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Title: The nature of living matter
Author: Lancelot Hogben
Release date: April 6, 2026 [eBook #78368]
Language: English
Original publication: London: Kegan Paul, Trench, Trubner & Co., Ltd, 1930
Other information and formats: www.gutenberg.org/ebooks/78368
Credits: Sean (@parchmentglow)
*** START OF THE PROJECT GUTENBERG EBOOK THE NATURE OF LIVING MATTER ***
THE NATURE
OF LIVING MATTER
BY
LANCELOT HOGBEN
_Professor of Social Biology in the University of London_
The mind that needs to know all things must needs
at last come to know its own limits, even its own nullity,
beyond a certain point.--D. H. Lawrence
LONDON
KEGAN PAUL, TRENCH, TRUBNER & CO., LTD.
BROADWAY HOUSE: 68-74 CARTER LANE, E.C.
1930
Made and Printed in Great Britain by
Butler & Tanner Ltd., Frome and London
To
BERTRAND RUSSELL
FOREWORD
In the summer of 1929 I was asked to speak for thirty-five minutes
in a symposium on the Nature of Life arranged by the officers of the
Physiological Section of the British Association. I soon discovered
that there are many ways of filling up thirty-five minutes devoted to
the consideration of so formidable a topic. Eventually I decided to
make my contribution in the form which appears almost unchanged in the
fourth essay of this book. By that time I had written a volume without
intending to break my silence before attaining my sixtieth year. With
the insertion of some material to elaborate the point of view I had
developed this collection might be described as the rejected addresses.
I owe to my friend Mr. Sewell, who has adopted the same standpoint in a
criticism of æsthetics in course of preparation, the suggestion of the
word _public_ in contradistinction to the _external_ world of Professor
Eddington.
Four contributors to the Symposium on the Nature of Life, General
Smuts, Dr. Haldane, Dr. Wildon Carr and Professor Eddington, had
already published their philosophical views in book form. General
Smuts and Dr. Haldane courteously wrote to me, expressing the hope
that I would criticize their views destructively. I found the time
at my disposal insufficient for stating my own point of view. I have
responded to their invitation in these essays. If certain passages
seem to some of my readers unduly polemical, I have the assurance that
my fellow-contributors will regard this collection as the continuation
of what was a very friendly argument.
I wish to acknowledge my indebtedness to my friend Professor Levy for
criticism and assistance in seeing this book through the press.
L. T. H.
Cape Town,
_April, 1930._
CONTENTS
PART I
VITALISM AND MECHANISM
Summary 1
Introduction 3
I: The Mechanization of Consciousness 33
II: The Atomistic View of Parenthood 56
III: The Nature of Life--an Introduction to the Theory
of a Public World 80
IV: The Concept of Adaptation 102
PART II
DARWINISM AND THE ATOMISTIC INTERPRETATION OF INHERITANCE
Summary 127
V: The Methodology of Evolution 129
VI: The Problem of Species 151
VII: Natural Selection and Experimental Research 170
VIII: The Survival of the Eugenist 193
PART III
HOLISM AND THE PUBLICIST STANDPOINT IN PHILOSOPHY
Summary 217
IX: Biology and Humanism 219
X: Publicity, Reality, and Religion 245
XI: Privacy, Publicity, and Education 266
XII: The Publicist Standpoint and Holism 289
PART I
VITALISM AND MECHANISM
SUMMARY
An uneasy recognition of the conflict between science and common sense
in our generation has rekindled interest in the relation of science to
moral philosophy. In this awakening the physicists have assumed the
leading part. It will not be possible to predict the outcome, until the
contribution of contemporary biology to natural philosophy is taken
into consideration. Some writers have expressed the hope that the
influence of biological concepts may assist to a reconciliation of the
claims of natural science and moral philosophy. This hope is based on a
failure to recognize that modern experimental biology is an ethically
neutral body of enquiry. The merits of a mechanistic or vitalistic
outlook in biology have been too often discussed from an ontological
rather than an epistemological standpoint. Our estimate of the
influence of biological concepts on the future of natural philosophy
must be guided by a recognition of the essential similarity of method
in biology and physics. This similarity is nowhere more evident than
in those branches of physiology which lie most conspicuously outside
the realm of applicability of physico-chemical hypotheses. Traditional
mechanistic physiology has accepted the Cartesian dualism of mind and
matter. The modern physiology of the conditioned reflex has undermined
the distinction between reflex and voluntary behaviour. There is thus
no nicely defined boundary at which physiology ends and philosophy
begins. Biology is annexing regions of enquiry which have hitherto
remained the province of moral philosophy. As a concept of biology
_Mind_ is replaced by _Behaviour_. Since modern biology claims to
interpret the characteristics of conscious behaviour as properties of
physical objects, the advance of biological science cannot be expected
to reinforce the claims of moral philosophy. How far it is possible
to reduce the interpretation of behaviour to purely physico-chemical
hypotheses, we have no means of predicting. At present we can foresee
no limit to progress in that direction. The significant issue is not
the completeness of the mechanistic solution, but whether there exists
any definable method of arriving at a more complete solution than the
mechanistic outlook permits.
* * * * *
“It is our happiness to live in one of those eventful periods of
intellectual and moral history when the fast-closed gates of discovery
and reform stand open at their widest. How long these good days may
last we cannot tell. It may be that the increasing power and range of
scientific method with its stringency of argument and constant check
of fact may start the world in a more steady and continuous course of
progress than it has moved on heretofore. But if history is to repeat
itself according to precedent, we must look forward to stiffer, duller
ages of traditionalists and commentators, when the great thinkers of
our time will be appealed to by men who slavishly accept their tenets,
yet cannot or dare not follow their methods through better evidence
to higher ends. In either case it is for those among us whose minds
are set on the advancement of civilization to make the most of present
opportunities that, even when in future years progress is arrested, it
may be arrested at a higher level.”
Tylor’s _Primitive Culture_
INTRODUCTION
§1
No one who is familiar with contemporary thought can have failed to
recognize two characteristics which have emerged into prominence during
the past two decades. With increasing elaboration of its logical
technique, science has been brought into apparently irreconcilable
conflict with common sense. The result is that scientists, uneasy
in the realization of this conflict, are seeking to establish a new
working relation between science and philosophy. This _rapprochement_
has been brought about especially through recent progress in physics.
It will not be possible to predict its outcome so long as the physicist
claims to speak for science as a whole. In this introductory essay I
propose to discuss in a somewhat discursive and preliminary way how far
the conflict between science and common sense is apparent rather than
real, and to indicate the special need for reviewing the progress of
modern biology in its philosophical bearings.
At the present time few biologists are anxious to court publicity
in the field of philosophic controversy. Those who do so are rarely
numbered among the ranks of those who are still actively contributing
to contemporary progress in biological enquiry. Those who are actively
contributing to the advancement of biological knowledge show little
disposition to commit themselves to far-reaching generalizations.
There has emerged from the morass of speculation associated with the
rise of the evolutionary hypothesis a recognition of the paramount
importance of painstaking quantitative study of limited aspects of
vital phenomena. This attitude is a salutary one. It does not signify
that biology is passing through a phase of stagnation. On the contrary
current biological discoveries contain the germ of philosophical issues
which may prove to be as revolutionary as Relativity and as repugnant
to common sense. In the essays which follow I shall confine myself
to accredited experimental data. I do not pretend that all or even
a majority of biologists will agree with my interpretation of their
philosophic significance.
There is no novelty in asserting the need for incorporating the
contribution of biological science in a modern philosophical outlook.
Herbert Spencer and the Evolutionists prepared the ground fifty years
ago; but they failed to lay emphasis on the methodological aspect of
biological enquiry. The methods and not the results of biological
science are specially significant to philosophical discussion. In
putting forward my own views upon the nature of life, it is not the
results of biological enquiry, but the methods which I propose to
discuss in the first series of essays in this volume. In contrasting
the methods and concepts of physical and biological science, I shall
sometimes draw inferences which will not commend themselves to the
judgment of biologists for whose contributions I entertain a lively
respect. I shall not be surprised to be told that my forecast of the
outcome of biological enquiry is pretentious, and that my philosophical
conclusions are in conflict with common sense.
At an early age I abandoned the conviction that scientific hypotheses
must conform to the requirements of common sense. When I was a boy,
there used to be in Portsmouth, the town of my nativity, a public
figure by name Ebenezer Breach. Mr. Breach was a philosopher. To be
precise he described himself as “Natural Astronomer and Poet.” In that
he belittled his gifts. Of his poetry I shall say nothing, save that he
stated the qualification “poet by Royal Patronage” in his fascinating
brochure _Twenty Reasons against Newtonianism or The Universal
Challenge to Unnatural Science_. This was sold for the modest price
of twopence sterling. As his contribution to modern thought may be
unfamiliar to many cultivated people who were not born in Portsmouth, I
propose to quote the first of his twenty reasons as representative of
the system he develops:
“Because the earth has no axis, therefore nothing on which to
revolve, an imaginary mathematical line is substituted. But no
solid body could revolve on an imaginary axis or line. It is an
imaginary cause which can only produce an imaginary effect, so all
that follows the cause must be imaginary. If anything be placed on
the top of a revolving body it will fly off at a tangent.”
From this you might infer, wrongly it happens, that Mr. Ebenezer
Breach earned a comfortable livelihood as Regius Professor of Moral
Philosophy in an authentic University. He had in fact chosen to bear
witness to the hope that was in him by the only alternative which a
harsher economic destiny had imposed. Every Saturday night he addressed
a handful of half-intoxicated seamen, tired commercial travellers,
adventurous nursery maids and irreverent pupil teachers foregathered
on the sea-front. There he occasionally succeeded in selling a copy
of the _Twenty Reasons_, and beyond this obtained, as far as I am
aware, no reward in the life that now is. In spite of his erudition and
distinction of person, Mr. Breach, the prophet of common sense, did
not make many converts. He was less successful in his popular appeal
than an evangelical competitor who used to minister to Portsmouth beach
before a banner whose legend stated, “the wages of sin is death.”
This banner I can still recall as, in its way, a work of art. On the
foreground were displayed the theatre, race-course, public-house,
dancing saloon and gaming tables along the edge of a precipice over
which poor folk in a semi-incandescent condition were tumbling into a
lake of brimstone and fire. It invariably drew a large crowd. I had
early imbibed the notion that science like Sunday travelling, whist and
dramatic entertainment is worldly, so that the gospel of Mr. Breach,
who condemned science on account of its essential unworldliness,
presented a new and arresting point of view. On the whole the
inhabitants of Portsmouth were more interested in their souls and what
would become of them after death. Mr. Breach had another competitor
with more peculiar views about the soul and about life. As far as I
can remember he held that the brain secretes consciousness in much the
same way as the liver secretes bile, and he asserted that the soul
was the shadow cast by the machine. My nurse held very definite views
about his domestic life. He was a materialist, and in all probability a
polygamist, if not worse. Mr. Breach who was a bachelor, the evangelist
who was certainly not a polygamist, and the Secularist who was
undoubtedly a bad man all agreed in one particular. Each believed that
the gospel he proclaimed was common sense.
Of the Flat Earth faith Mr. Ebenezer Breach is the only Confessor and,
financially speaking, Martyr I have been privileged to encounter. I
cherish the recollection of his secular ministrations for a reason
which is eminently relevant to everything which I propose to say about
the bearing of current biological concepts on philosophical discussion.
At an age when, to my way of thinking, Punch and Judy were the only
serious rivals to the magnetism of his stupendous intellectual
gifts Mr. Breach stands out in the sharp relief of retrospect as the
Forerunner of the coming conflict between science and common sense.
I have already remarked that the uneasy recognition that science
conflicts with common sense has been the keynote of philosophical
controversy during the past decade. Curiously enough some scientists
seem to regard this as a grave disability on the part of science.
They feel compelled in consequence to adopt an apologetic attitude
to the claims of traditional philosophy. Perhaps this is because the
protagonists of science in the nineteenth century made it their proud
boast that science is nothing more than organized common sense. They
therefore felt that they had the man in the crowd on their side. Even
Herbert Spencer, prophet of evolution, when evolution was still a
subversive doctrine, could soberly declare that “the ultimate truth of
a proposition is the inconceivableness of its negation.”
Neitzsche includes this quotation in the _Will to Power_ as one of his
“inscriptions over the porch of a modern lunatic asylum.” It is only
necessary to mention the word Relativity to indicate how impossible it
would be for a natural philosopher to express himself in similar terms
to-day. The situation which has been created by progress in modern
physics is not without parallel in human history. It is true that
the new theories have employed an immensely elaborate and difficult
logical technique. How far they can be simplified it is at present
impossible to predict. Newton’s fluxions were unfamiliar to his
contemporaries. The author of the _Principia_ devoted a good deal of
time to a geometrical presentation of his ideas, in order to make them
accessible to his generation. For more than a century after Newton’s
death the calculus remained a preserve for mathematical specialists.
To-day a knowledge of the calculus requisite to an elementary
understanding of the theory of elliptical orbits lies within the scope
of the first year’s work at a university, if it has not been acquired
in the higher forms of a good school. It is conceivable that the
mathematical development of modern physical theories will be simplified
in the course of time. In that sense the esoteric stage through which
physics is now passing may be a temporary phase. The essential feature
of the conflict between common sense and physical science in this
generation lies in the unfamiliarity of the new concepts. The conflict
between common sense and the new biological concepts shares the same
characteristic.
In Bernard Shaw’s _St. Joan_, La Tremouille asks: “Who the deuce was
Pythagoras?” “A sage,” replies the Archbishop, “who held that the earth
is round and that it moves round the sun.” “What an utter fool,” says
La Tremouille, “couldn’t he use his eyes?” La Tremouille here calls
attention to a fact that was overlooked by Herbert Spencer, by Mr.
Ebenezer Breach and by those Relativist philosophers, who, being unable
to convince the man in the crowd, indulge in the luxury of wondering
whether the claims of scientific method have been pushed too far.
Common sense is another name for what good citizens are prepared to
accept without argument. Scientific ideas only conflict with common
sense so long as they are still new and unfamiliar. Mr. Breach was in
advance of his time in daring to criticize the Newtonian system. He was
behind his time in thinking that Newton’s position could be assailed
successfully with the weapons of common sense. The essential rightness
of the Newtonian system had already become incorporated in British
middle-class respectability. To the rising generation suckled on Mr.
Wells’ _Outlines_ evolution is common sense. Two generations have
elapsed since, as La Tremouille would say, any fool who used his eyes
could see that a bishop was a product of special creation. The man in
the crowd has no clearer notion of the logical status of the doctrine
of descent than had his grandfathers who implicitly accepted the story
of the Fall.
The phenomenal success of those who set out to popularize the Theory
of Evolution makes it easy to overlook the circumstance that evolution
was wholly repugnant to common sense within the memory of those who
are still living. The outburst of public controversy which greeted its
announcement has no parallel in this generation. In consequence its
impact upon traditional philosophy has been far less apparent than
its influence upon religious dogma and social theory. The younger
generation of biologists cannot recapture the first fine raptures of
enthusiasm which their elders experienced. The prevailing attitude is
to welcome a return to the complacent dualism of pre-Darwinian days,
when scientists did not meddle with philosophy and metaphysicians
conceded to scientists the right to go to the devil in their own
way. Although this view is widely held, I do not believe that the
philosophical implications of evolution have ever been thoroughly
explored; or that it was possible to do so, while the study of animal
behaviour was still dominated by the language of introspective
psychology. By explaining the secular origin of philosophers Darwin
bequeathed to us the task of elucidating the anatomy of philosophy.
In the opening years of the present century, science had already
lost that truculence which one associates with the generation of
Huxley and Tyndall. It had surrendered its tradition of fearlessness
and candour. Academic philosophy, liberal theology and utilitarian
science went their placid ways without mutual interference. Bergson,
a philosopher more widely known than Mr. Ebenezer Breach, had cast
a pebble of _belles lettres_ into the mill-pond of compromise. The
indifference with which it was greeted by those engaged in the task
of placing the evolutionary problem upon a secure foundation of
experimental data is a measure of the esteem which they entertained
for it. It has been interpreted as assent by some contemporary writers
who are not themselves biologists. In _Science and the Modern World_
Dr. Whitehead even speaks of Bergson’s “instinctive grasp of modern
biology.” A modern biologist engaged in the study of behaviour would
refer with greater caution to Madame Blavatsky’s instinctive grasp
of modern astronomy or Mahatma Gandhi’s instinctive grasp of modern
economics. He would regard the instinctive grasp of any branch of
scientific knowledge with more suspicion than approval. No biologist
has undertaken the task of examining the philosophical implications
of Darwin’s doctrine in the light of contemporary progress in the
experimental analysis of living matter.
§2
Under the influence of Hegel, academic philosophy left the scientist
to his own devices. To-day the physicist has again driven the idealist
philosopher out of his retreat. He has compelled him to take account of
a conceptual world which we all recognize whenever we consult a railway
time-table or book a passage in an ocean liner. Secure in the prospect
of fresh philosophical victories, the astronomer surveys the world with
a blind eye to the microscope, and magnanimously dictates the new
territorial frontiers of science and moral philosophy to the advantage
of the latter. It has been customary in the past, and therefore common
sense, to assume that the issues with which moral philosophy deals are
more fundamental than those which fall within the scope of natural
science. It is an assumption which, whatever its meaning, does not
hamper the advance of pure physics; but the biologist is not bound to
accept this convention when it restricts his own field of enquiry. A
philosopher is a particular kind of organism. Philosophy itself might
therefore be regarded as an aspect of the behaviour of a piece of
living matter. The study of the properties of living matter is the
province of the biologist. From this point of view the study of biology
is more fundamental than the pursuit of moral philosophy.
The physicist brings to the discussion of philosophy the discipline
of an older branch of enquiry with a more elaborate logical technique
than that of biology. His claim to speak for the whole field of science
should be scrutinized with a critical eye. I am sure that Professor
Eddington will agree with me, when I say that the biologist has a
specific contribution to make to what he has aptly called the “world
symposium.” I am also confident that many biologists will agree with
me, when I state that the contributions of the Relativist philosophers
rarely display a profound understanding of the kind of problems
biologists are now attempting to solve, and the way in which the modern
biologist sets about his task. A quotation from Mr. Sullivan’s _Bases
of Modern Science_, a stimulating and provocative book, will illustrate
my meaning. Mr. Sullivan, whose physics I do not venture to criticize,
states: “The primary concepts in terms of which the science of physics
is constructed... have to be supplemented by others in the science of
chemistry, and for the sciences of life and mind, are so far from being
sufficient, that they have hardly yet been found to be relevant.” Half
a century has passed since the concept of chemical affinity was annexed
by thermodynamics, and the most conservative physiologist could hardly
refrain from ridiculing the latter part of this quotation. Professor
Eddington himself has adopted the “Principle of Indeterminacy” as an
_ad hoc_ hypothesis in a limited field of enquiry. From it he proceeds
to draw conclusions about human responsibility and the doctrine of free
will. These are topics which lie nearer to the province of biology than
physics. It would be well to await the verdict of biological science
before accepting inferences of so far reaching a character as those
which Professor Eddington has advanced.
By emphasizing the conflict between science and common sense Relativity
has engendered a new interest in the relation of science to moral
philosophy. To view that relation in its proper perspective the
concepts of modern biology must supplement the concepts of modern
physics. I am not suggesting that this need is overlooked by those
who are not biologists. Dr. Whitehead has gone so far as to advocate
replacing the traditional physical idea of matter by the biological
concept of organism, or as a modern biologist might prefer to say,
behaviour. When he expresses the hope that this will assist to “end
the divorce of science from the affirmations of æsthetic and ethical
experiences,” it is clear that his conception of the nature of
biological enquiry dates from Herbert Spencer and differs from that
which contemporary biologists would generally be willing to accept.
Owing to the separation of descriptive from experimental biology, a
separation for which the evolutionists were pre-eminently to blame,
a well-informed interest in the study of living matter is more rare
among physicists of our period than it was in the days of Robert Hooke
and Boyle or of Euler, Lavoisier, and Laplace. I am convinced that
very few scientists who are not biologists--perhaps no professional
philosophers--possess a clear notion of the way in which the modern
experimental biologist approaches the study of the organism and the
results at which he aims.
I have already suggested that there are special reasons why the
concepts of biology stand in a more intimate relation to the scope of
moral philosophy than do those of physical science in the restricted
sense. It is difficult to define the meaning of philosophy without
implying a particular point of view about the limitations of human
knowledge. There are as many different definitions of philosophy as
there are different schools of philosophical opinion. From the point of
view of the materialist a Hegelian is a sea lawyer. From the point of
view of the subjective idealist a materialist is not a philosopher at
all. If there is anything which all the two and seventy jarring sects
would agree to regard as a problem of philosophy, it is the Nature of
Life. If we are to avoid making any unjustifiable assumptions about the
nature of knowledge, we must for the present define a philosophical
discussion of the Nature of Life as the most comprehensive treatment of
the problem. It does not necessarily follow that there is any essential
difference between a scientific and a philosophic enquiry in this sense.
When people first hear their own voices recorded by a gramophone, it
is well known that they are often--like myself--a little humiliated,
and generally somewhat surprised. I once had occasion to witness an
instructive incident which occurred in the phonetics department of
the University of Cape Town. A gramophone record of three men engaged
in a conversation was prepared. None of the three participants had
previously listened to a record of his own voice. When the record
was completed each man agreed that the voices of the other two were
faithfully recorded. Each man denied that his own voice had any
semblance to its representation by the recording instrument. This
simple experiment in human behaviour illustrates what I shall later
call the distinction between the _private worlds_ and the _public
world_. It also illustrates a fundamental divergence of outlook which
distinguishes two tendencies in philosophical discussion, and makes
it difficult to give any definition of philosophy satisfactory to all
parties. One school of philosophers defines a good record as a record
which on the whole faithfully conveys the impression of human voices.
The philosopher of the opposing school feels that it ought to be
possible to manufacture a record which will faithfully represent the
voice of his opponent, while at the same time registering his own voice
as he hears it himself, when he is speaking, and would prefer other
people to hear it.
This distinction has an interesting history which will be discussed in
the third series of essays in this volume. Greek speculative philosophy
had its first beginnings in a secular curiosity about Nature.
Science and philosophy were thus one and the same thing to Thales,
to Empedocles or to Democritus. In Greek thought speculation was not
sufficiently disciplined by sustained observation of Nature. For that
reason it gave birth to innumerable conflicting hypotheses which could
never be made the subject of decisive tests. Out of this confusion of
conflicting ideas was born a reaction against science. Philosophy
turned from the slow and tedious task of examining the actual world
to the more facile and pretentious pursuit of an ideal world. In
the person of Plato it forfeited its secular temper. Science was
introduced into modern Europe by the Arabs, who assimilated the secular
curiosity of the Greeks. Ecclesiasticism seized upon the speculations
of the later Greek philosophers to provide a rational basis for
theological dogma. Since mediæval times scientists have submitted
to an arrangement which gives to those who have not studied Nature
the right to supervise the logical status of their conclusions. The
stability of this arrangement has been maintained by the circumstance
that human beings are far more interested in themselves than in any
other material objects. Greek materialism declined, because it could
not satisfy man’s curiosity about himself. The success of its rival
was not due to its ability to settle the problems of human nature and
social conduct. It succeeded because human nature demands a forum for
the ventilation of its grievances. Science has been most successful
in the past in dealing with inanimate things. Only in comparatively
recent times has the phenomenal success of scientific method, fortified
by the secular influence of Darwin’s teaching, encouraged the belief
that it might be applied to the study of man’s behaviour and social
organization. The belief that a philosophical discussion of the Nature
of Life lies beyond the province of the biologist is due to centuries
of subservience to a tradition which has identified philosophy with
the interests of statesmanship and ecclesiasticism. If the method of
science is applicable to the study of how statesmen and theologians
behave, it is legitimate to undertake a discussion of the nature
of life without assuming that the biological standpoint must be
reinforced by the discipline of scholastic philosophy.
There is a further assumption which we need not make in our enquiries
into the Nature of Life. We need not presume like Socrates that all
questions about life are permissible. A proper respect for our own
limitations is as essential to philosophy as to sanity and modesty in
everyday life. It is only possible to formulate questions in the right
way when we already have at our disposal a good deal of information
relevant to the correct answer. This was not recognized by the
materialists of the nineteenth century when they attempted to give a
common-sense solution of the Riddle of Life. To-day it is customary to
refer to materialism as an exploded fallacy. If instead of looking at
the way in which the materialist attempted to answer the man in the
crowd, we examine the way in which he attempted to answer the questions
which he himself propounded, the explosion of the fallacy is not so
encouraging to traditional beliefs. The term materialism, when it is
not employed like Bolshevism as a term of abuse, is loosely applied to
a constellation of beliefs, some of which concern the Nature of Life
and some of which concern the Nature of Knowledge. In the latter sense
materialism implies the conviction that the only genuine knowledge is
that which can be gained by pursuing the method devised by scientists
for the study of what are ordinarily called material objects. If this
conviction is carried to its logical conclusion, a discussion of the
Nature of Life in language which is intelligible to the audience of
Mr. Breach or his Secularist competitor is impossible. The materialist
who attempts a common-sense solution of the Riddle of Life is
inconsistent with his materialism. It is his inconsistency and not his
materialism which is an exploded fallacy. Common-sense materialism,
the materialism which is an exploded fallacy to-day, was based on the
belief that a plain answer to a plain question is the inalienable
birthright of the plain man. Secularist rationalism was the offspring
of Protestant democracy. Protestant democracy is suspicious of the
expert, who is the person who knows that there is a technique of asking
questions in the right way as well as a technique of answering them
in the right way. Perhaps Xanthippe, who has become the symbol of a
nagging wife, realized this profound truth more clearly than Socrates.
Perhaps her short way with introspective philosophers was based on a
considered recognition of human frailty, and experience of children.
An intelligent child of three once asked me to tell her the colour of
Wednesday. To the more sophisticated adult the question is ridiculous,
though I suppose the theosophist would regard it as permissible.
Metaphorically speaking, the habit of asking the colour of Wednesday
is not exclusively confined to children. Thousands of years ago human
beings began to associate particular sounds with objects around them,
so that these sounds became signals for activities. These activities
became increasingly more complex as articulate speech became more
elaborate. Gradually human beings ceased to employ a separate symbol
for every object around them. They began to condense and economize,
abstracting separate properties. It became no longer necessary to
have separate words for white cow, black cow, white horse and black
horse. In effecting this economy it was inevitable that new words with
no clear relation to experience were often invented. Common language
the world over is burdened with words which effect no economy of
discourse. Anyone who has not realized this may perform the simple
experiment of asking six educated people to define in writing on a
folded slip of paper the meaning of the word _sincerity_. With the
coming of civilization man invented a new form of symbolism, the
language of science. In spite of immense social inertia this symbolism
has become more and more important, because of the tremendous power
for controlling nature which it has given us. In the invention of this
new language not only sustained observation of nature, but active
interference with nature, or experiment, is enlisted in the process of
abstraction.
Because common language and the language of science are not the same
thing, there never can be a plain answer for the plain question of the
man in the crowd. There can only be a familiar one. In any restricted
field of scientific enquiry confusion of thought is avoided by the
introduction of new symbols to denote new experience, or a preliminary
re-definition of old symbols, if these are employed. So long as the
chemist is only concerned with the reducing power of a particular
sugar, it is sufficient for him to describe it as dextrose. When he
directs his attention to the optical properties of the sugars he finds
this symbol no longer adequate to define a homogeneous class, and
distinguishes between α dextrose, β dextrose and so forth. When
scientific hypothesis so broadens its channels as to merge into the
general current of human thought, the scientist finds himself dealing
with matters for which there already exists a vocabulary, but one that
has none of the precision of scientific nomenclature, one called into
being by an approach to experience which has none of the disciplined
restraint which scientific method imposes. That is why the practising
scientist is sometimes compelled to treat the conundrums of humanistic
philosophers like the question of the child who wanted to know the
colour of Wednesday. Concerning those things about which we talk most
our language is apt to be least definite.
§3
One of the things about which we talk most is life itself. A discussion
of the Nature of Life presupposes that we mean something quite
definite, when we use the term life. The familiar lines of Mr. Belloc
suggest a helpful analogy to illustrate the nature of a scientific
definition:
“Here you may put with critical felicity
The following question, ‘What is Electricity?’
‘Molecular activity,’ say some.
Others remain silent or are dumb.”
What is electricity?--is a plain question. It is only possible to
give it an intelligible answer when we translate it into the form,
what conditions determine electrical phenomena? A scientific concept
is a label for a class of properties which can be investigated
scientifically. Though this happens to be a cardinal doctrine of
modern logicians, it is also a commonplace of scientific thought,
when undisturbed by ulterior considerations. It is a commonplace
which is constantly overlooked by biologists as well as laymen in a
discussion concerning the nature of life. The temptation to overlook
it is assisted by the custom of spelling nature and life with capital
letters, a practice to which what the Melanesians call _mana_ adheres.
The only intelligible significance of the word Life in scientific
discussion is to denote collectively the properties of living[1] things.
The word life is variously employed in common language. To Mr.
Mantalini life is one demmed {sic} thing after another. Every
biological student is familiar with the experiment of removing a
frog’s heart from its body, maintaining its beat by perfusing it
with a suitable saline medium, arresting its rhythm and restarting
it by changing the constituents of the medium. This can be performed
repeatedly for many hours after the owner of the heart is, legally
speaking, dead. The layman confronted with this commonplace of the
laboratory invariably asks with some show of bewilderment, “Is it
alive?” It is extremely difficult to answer him in words he will
understand. He has been accustomed to think of an organism as a whole,
just as we think of solid matter as a whole. Unaided common sense
does not easily grasp the notion that the frog’s heart displays the
characteristic properties of living matter, after the frog, considered
as a whole, has ceased to display those characteristics of living
matter which we associate with whole frogs, when we say that they are
alive.
In biological discussion the nature of life can only be understood
to mean the characteristic properties of living things, how they are
related to one another and to the properties of non-living matter, how
they have come into being. To those who are accustomed to thinking in
abstract nouns and capital letters this way of defining life will seem
rather like the well-known definition of an archdeacon as a man who
discharges archidiaconal functions; but if life is only a convenient
label for the properties of living matter, we have foreshadowed an
important conclusion. Those who declare that materialism is an exploded
fallacy are usually those who deplore the judicial separation of
science and moral philosophy. If they entertain the hope that biology
is likely to effect a restitution of conjugal rights, they evidently
imply that life to the biologist means something more than the
properties of living matter. They assume that a biological concept of
life contains other implications of its use in common language.
The source of this confusion is easy to understand. The biologist
can no more avoid using the word life than the physicist can avoid
using the word matter in a loose and arbitrary sense in everyday
conversation. Whatever meaning the biologist may attach to the term
life, when he is exercising his domestic and political activities,
there is only one legitimate manner in which he can employ it in
his capacity as a scientist. Much discussion between the opposing
schools of vitalists and mechanists is utterly barren, because this
fundamental issue is not clearly defined at the outset. The vitalist
can legitimately attack the mechanist by pointing out that living
things have characteristic properties other than those which the
mechanist attempts to analyse. If he does so, he must specify what such
properties are. In the laboratory the biologist carries out his work
on the same lines, whether he calls himself a vitalist or a mechanist.
On the platform he may, and frequently does, overlook this. The layman
may thus acquire a disproportionate estimate of the extent to which
biologists differ among themselves about fundamental issues.
That biologists are still less unanimous than chemists in the hope of
resolving, in more universal terms, concepts traditionally restricted
to their own fields of enquiry, may be attributed to the complexity of
their subject matter. Biology is a younger science, and a vast amount
of purely descriptive work was necessary, before it was possible to
formulate the mechanical problems which living matter presents. This
task requiring considerable specialization in the descriptive study
of the exclusively geometrical aspects of the configuration of living
systems unhappily became divorced from the more fundamental issue of
biological enquiry. The physical analysis of the properties of living
matter is a problem necessarily spatio-temporal in its extension,
experimental in its method, and quantitative in its grammar. The
spectacular success of evolutionary speculation during the nineteenth
century preceded the birth of quantitative and experimental researches
on inheritance and variation, giving descriptive biology a reflected
glory on account of the far-reaching cosmological consequences of the
doctrine of descent.
By encouraging the hope of reconstructing the pedigree of mankind,
Natural Selection widened the gulf between descriptive and experimental
enquiry; and provided a satisfactory modus vivendi for two diverging
and independent schools of research. Anatomy claimed the relation of
one type of living being to another. Physiology concerned itself with
the relation of living matter to inanimate objects. During the present
generation evolutionary problems have emerged to the forefront of
experimental enquiry. Heredity and variation are no longer axioms with
which the taxidermist and the osteologist can conjure unchallenged.
Experimental biologists are grateful to those who have compiled
the Who’s Who of the Animal Kingdom. They refuse to concede that
the execution of this task implies a profound understanding of the
principles of political economy. Naturally the anatomist and the field
naturalist view the change with a jealous and suspicious eye.
Biologists agree among themselves in recognizing that the approach to
the organism as a physical object has led to many valuable discoveries;
and that the application of physical methods to the study of the
organism permits us to make many predictions about the behaviour
of living systems with as much confidence as we have in predicting
other secular events. In so far as recent investigation has probed
into phenomena which it has been customary to place beyond the limit
of applicability of physical methods and concepts to the analysis
of the properties of living matter, it is not surprising that many
biologists have failed to take stock of the situation. They may simply
deny that certain aspects of the behaviour of organisms can be treated
successfully by the traditional methods of experimental physiology. If
they do, it should be sufficient to set forth the new evidence at our
disposal. When they go further and assert that certain characteristics
of living things properly belong to the sphere of traditional
philosophy, it is permissible to entertain the suspicion that they
share the all too human desire to be _certain_ rather than to _know_.
The chief source of disagreement between different schools of opinion
in any discussion of the Nature of Life arises from the difficulty
of defining another concept which is intimately connected, but not
necessarily co-extensive with, that of life itself. It has been
customary in the past to assume that the concept of _consciousness_
defines a field in which the methods of experimental physiology break
down and require to be supplemented by the method of introspection. In
so far as it bears on the Nature of Life this implies the possibility
of identifying and specifying in living systems characteristics to
which the term consciousness directs attention. It is impossible to
avoid disagreement in connexion with this concept without recognizing a
fruitful source of confusion. The statement “I (N or M) am a conscious
being” has a formal relation to the statement “All men are conscious
beings” like the analogous statement “Mr. Bertrand Russell is a
conscious being,” so long as it is understood that I and Mr. Bertrand
Russell are both single valued and members of the class “men.” From
this it follows that any implication of the first proposition which is
not implicit in the second defies logical analysis and therefore eludes
philosophical enquiry. For the purpose of philosophical discussion “I
am a conscious being” contains nothing that is not implied by saying
that “all men are conscious beings.” I shall use the term _public_
to signify this way of looking at the concept of consciousness. Any
residuum of the first proposition which cannot be formally identified
with the third and shown like it to be included in the second and
more general proposition is a _private_ affair of the individual.
If we find that modern physiology has undertaken to investigate
those characteristics of the behaviour of living systems associated
with the term consciousness in its public sense, a new horizon of
philosophical discussion is unfolded. If physiology is more successful
than introspective philosophy in defining predictable conclusions about
living behaviour, we have no need to go outside the data of physiology
for the materials of a comprehensive discussion of the Nature of Life.
A philosophical discussion of the Nature of Life will only be more
comprehensive than a biological discussion of the Nature of Life in
the sense that more attention will be paid to the methods of enquiry
adopted.
Between two extreme schools of opinion existing at the present day the
issue, in so far as it is a tangible one to the practising biologist,
is thus defined by Dr. Haldane in his recent Gifford Lectures.
“We can of course leave the characteristic peculiarities of
conscious behaviour out of account, and regard persons from a
purely physical and chemical point, as weighing so much, as
yielding certain amounts of various proteins and other chemical
substances, distributed in a certain way, and as in various ways
continually converting potential into kinetic energy. This mode
of regarding persons is of great practical use for engineering
and other purposes, _but tells us nothing, however far we may
extend it, regarding the distinctive_ characters of conscious
behaviour...” (italics inserted).
In this passage Dr. Haldane is perfectly definite in stating where,
as he believes, the methods of traditional physiology cease to
be applicable. It is peculiarly felicitous that he uses the term
conscious behaviour rather than consciousness in this connexion. If
we find reason to believe that “conscious behaviour” can be analysed
with reference to a space-time framework by the methods of physical
science, Dr. Haldane’s attack on the mechanistic position falls to
the ground except in so far as he can refuse to capitulate until the
problem has been reduced to a question of pure physical chemistry. In
the succeeding essay on The Mechanization of Consciousness I shall
endeavour to show that in our generation the work of Pavlov’s school
has successfully tackled, for the first time in history, the problem of
what Dr. Haldane calls “conscious behaviour” in non-teleological terms.
It has reduced it to the investigation of the conditions under which
new reflex systems are brought into being.
In _Science and the Modern World_ Professor Whitehead states that
the “effect of physiology” on philosophical discussion has been
“to put mind back into nature.” I presume that he is referring to
the traditional distinction between reflex activity and voluntary
behaviour. It is true that physiology has accepted this distinction
which it inherited from the dualism of Descartes; but traditional
physiology never attempted to probe deeply into the nature of
voluntary behaviour. It was content to investigate reflex activity,
and concede the prerogative of discussing the characteristics of
conscious behaviour to moral philosophy. _Experimental physiology
like experimental physics is an ethically neutral science._ If Pavlov
has reduced the problem of conscious behaviour to the same level
of discussion as the problems of reflex behaviour, the traditional
distinction between reflex and voluntary activity has ceased to define
the boundary at which physiology ends and moral philosophy begins. If
the investigation of the characteristics of conscious behaviour can
be brought within the scope of an ethically neutral method, we must
abandon any hope that biology can assist to end “the divorce of science
from the affirmations of æsthetic and ethical experiences.” If the
Relativists can say that modern physics has given materialism its death
blow by referring solid matter to an atomic nexus of conceptual fields
of force which only exist in our consciousness, the physiologist can
add that modern biological enquiry is disintegrating consciousness into
an atomic nexus of reflex arcs. If modern physics has shown that we
can no longer think profitably of solid matter as existing in the way
in which it presents itself to common sense, modern biology is showing
that for the purpose of profitable discourse mind itself does not exist
as the essential unity which it assumes to common sense. If the advance
of science has disposed of the older forms of materialism, it is also
disposing of the traditional forms of idealism and dualism at the same
time.
Biological science no less than physics is opening up new fields
for exploration in philosophy. The new approach to the problem
of “conscious behaviour” involves an intellectual effort no less
repugnant than the non-Euclidean space of the relativist. The new,
in preference to the traditional biological standpoint, owes its
sanction to the same test as that by which relativistic theories must
in the last resort be assayed. A disinclination to discuss “conscious
behaviour” and a tendency to assert dogmatically the possibility of
reducing it to purely chemical concepts has been characteristic of the
mechanistic standpoint in the past. It would seem that to emphasize the
applicability of physical methods to living matter in all its aspects,
a new term, free from this taint, is now needed. _Behaviourist_ has
already acquired certain restricted implications, and for reasons which
will be set forth in a succeeding essay I shall sometimes speak of
the _publicist_ in preference to the mechanistic standpoint. Unlike
the Flat Earth doctrine of Mr. Breach the publicist standpoint in
philosophy is not based on an appeal to common sense.
I began these introductory remarks by calling attention to two
characteristic features of contemporary thought, the uneasy recognition
of the opposition of science to common sense and the renewed search
for a working agreement between the claims of science and of moral
philosophy. In concluding, I would add a third to which I have not
explicitly referred. The scientist brought into collision with common
sense has for the time being lost his former air of self-confidence.
We are told that science does not deal with reality, that the external
world of physics is a shadow world, that the laws of physics are only
statistical generalizations, that scientific hypotheses are no more
than convenient devices to aid us in the practical business of living.
I cannot but feel that the solemnity of these assertions is out of all
proportion to their novelty. I cannot discover why recent developments
in physics constitute a specially cogent reason for reiterating them
at the present moment. I am disposed to believe that some of the
younger generation who have been familiar with the writings of Mach,
of Pearson, of William James and of Bergson, since they first began to
think about the nature of scientific knowledge, must share with me a
sentiment of surprise, when told that living scientists ever seriously
put forward those extravagant claims which, as we are now assured,
received their death blow from the theory of a relativity and the new
quantum mechanics. The apologetic attitude so prevalent in science
to-day is not a logical outcome of the introduction of new concepts. It
is based upon the hope of reinstating traditional beliefs with which
science was at one time in open conflict. This hope is not a by-product
of scientific discovery. It has its roots in the social temper of
the period. For half a decade the nations of Europe abandoned the
exercise of reason in their relations with one another. Intellectual
detachment was disloyalty. Criticism of traditional belief was treason.
Philosophers and men of science bowed to the inexorable decree of herd
suggestion. Compromise to traditional belief became the hall-mark of
good citizenship. Contemporary philosophy has yet to find a way out of
the intellectual discouragement which is the heritage of a World War.
The physicist has abandoned teleology in his own field. He has banished
the spiritual values from the domain of his enquiries. He now looks
to the biologist to shoulder the task of proving that the universe is
consonant with our notions of ethical propriety. I shall endeavour to
show that the progress of modern biology gives no justification for
the belief that such a compromise is possible. In approaching this
task my aim is not primarily to advocate the mechanistic conception of
life or to criticise the vitalistic standpoint. Controversy between
writers of the mechanistic and vitalistic schools has too often focused
attention on whether a complete solution of the Nature of Life can be
found within the mechanistic framework. The more significant question
is whether any solution can be obtained outside the mechanistic
framework. It may be interesting to know how far the biologist has
progressed in his enquiry into the Nature of Life. Philosophically it
is more significant to understand what methods of investigation have
permitted him to advance towards an admittedly partial solution of his
problem. To show that the mechanistic conception of life is inadequate
is one thing. To show that any alternative and more comprehensive view
can be gained by pursuing methods other than the traditional methods
of experimental biology is a more difficult task. It appears to me
that the mechanist can admit every criticism which the vitalist brings
to bear upon his case without weakening its essential strength. If
we commence our enquiries with the assumption that it is possible to
know everything, we shall be disappointed to find that the mechanistic
conception of life does not--and probably never will--find an answer
to every question which we may be tempted to propound. In that
disappointment lies the false security of the vitalistic standpoint.
It was the peculiar merit of Hume’s philosophy that he rejected the
necessity of making this assumption.
In assessing the respective contributions of the biological and
physical sciences to the construction of a Public World, we are
investigating the existence of certain characteristics common to all
branches of natural science. The method of science is not static. It
is ever growing and expanding, incorporating new territories within
its empire. For this reason formal definitions unfortified by an
examination of the historic past tend to be superficial and barren.
The origins of even the most exact sciences are deeply rooted in
the soil of magic. At any stage in the progress of human knowledge
particular features may be evident in more than one branch of enquiry.
As time goes on fresh similarities present themselves. The exact line
of demarcation between the already scientific and what is not as yet
scientific is therefore somewhat arbitrary. No definition of scientific
method is adequate unless it implies the recognition of a developmental
sequence in which new characteristics emerge successively into
prominence.
In the natural sciences, as customarily defined, it is essential that
the data shall be publicly accredited by the testimony of independent
observers. The observation and recording of publicly accredited data
is not in itself regarded as an adequate criterion of scientific
study, unless the data are arranged or classified in a particular way.
Such classification makes it possible to draw inferences which extend
beyond the range of the original data. The validity of the relations
implied in a particular classification is referred to their capacity
to permit us to predict verifiable conclusions. In practice it is
necessary to classify the data of a problem in a variety of ways before
it is possible to arrive at the type of classification which yields
relations satisfying this criterion of validity. This circumstance
assists us to draw a rough distinction between a type of enquiry
which is maturely scientific and one which is in process of becoming
scientific. In the older and more firmly established branches of
science, it is evident that severe economy in the initial assumptions
promotes the construction of hypotheses which are valid in the sense
defined. Ethical values have been eliminated altogether. The same
characteristics are increasingly recognized in newer departments of
scientific investigation.
When every criticism of the limitations of scientific method has been
accepted, the belief that philosophy can provide a means of solving
the problems which lie outside the realm of scientific enquiry still
remains to be proved. In the essays which form the third series of this
volume, I shall endeavour to discuss whether an enquiry into the nature
of reality has any intelligible meaning. With Hume I doubt whether it
is possible to attach any significance to deciding whether scientific
beliefs are a faithful representation of “reality.” Scientific beliefs
are specially characterized by their communicability, or, to use the
term which I shall employ more frequently, their _publicity_. The
fundamental problem of a philosophy which does not presuppose what
it sets out to establish is to find what characteristics of beliefs
make them communicable. It is by examining these characteristics
that we can hope to decide whether the discussion of our ethical and
æsthetic predilections can yield conclusions which have the same kind
of communicability as scientific beliefs, and, if that is possible,
in what manner such discussion must be conducted. I shall endeavour
to show that there is a confusion of meaning involved in discussing
whether the experiences with which science deals are more or less real
than the experiences which moral philosophy has claimed for its parish.
The more modest task of deciding whether the conclusions of science
have more or less communicability than ethical and æsthetic beliefs is
not a problem which necessarily eludes unprejudiced investigation.
I have indicated that an enquiry into the nature of life and the
nature of consciousness presupposes the necessity of formulating the
problem in the right way. This task is a necessary preliminary to
the analogous question, what is philosophy? The firefly emits light.
When we say that we understand what animal light is, we mean that we
understand what processes are involved in the production of animal
light. The method of science can lay bare the structures in which
luminescent materials are secreted and the physical transformation
of their chemical energy into visible radiation. Animal light is an
unusual characteristic of a species of insect known as the firefly.
The light of reason is a peculiar characteristic of certain human
beings known as philosophers. We can only say that we truly understand
philosophy or the light of reason, if we understand the processes which
confer upon philosophers their unusual characteristics. A philosopher
brought into being by the process of natural generation develops in an
environment which includes inanimate objects and other human beings.
He reacts to his physical environment by growth and to his social
environment by learning. If the method of science can assist us to
elucidate the processes of growth, learning and natural generation,
science can assist us to understand what philosophy is. The anatomy
of philosophy and the physiology of philosophers are inseparable. We
need not be discouraged in pursuing this line of enquiry, because the
answer which science can give us at present is incomplete. It is the
chief glory of science that its answers are always incomplete. The
pitiful failure of introspective philosophy resides in the finality of
its answers. Perhaps the most permanent influence of Relativity in the
history of philosophy will prove to be the challenge it issued to the
finality with which Kant enunciated the concepts of space and time.
I. THE MECHANIZATION OF CONSCIOUSNESS
“Now, in conclusion, the Method which teaches adherence to the
true order and an exact enumeration of the conditions of the
thing sought includes all that gives certitude to the rules of
arithmetic.”--Descartes, _Discourse on Method_
§1
The onus of proving that all the properties of living matter can be
reduced eventually to problems in physical chemistry or, on the other
hand, of denying that such will ever be accomplished, may be laid on
the shoulders of those who commit themselves to rash affirmations and
denials. If this were the only matter to decide, a discussion of the
merits of the mechanistic conception of life could reveal nothing more
than a temperamental difference between the disputants. A temperamental
difference does exist. The mechanist has a cheerful attitude to
knowledge and refuses to capitulate to the fear of the Unknown: the
vitalist, a sadder but not necessarily wiser type, finds balm in the
limitations and failures of human effort. The average biologist, who
has little sympathy either for the heroic or the desperate point of
view, maintains a detached scepticism.
Such scepticism has much to commend it; but scepticism no less than
piety can be employed as an excuse for mere intellectual laziness.
Between those who advocate the mechanistic conception of life and those
who reject it, there is a divergence of outlook more fundamental than
usually appears in the course of controversy. Whether the same set of
hypotheses will ultimately serve to interpret the properties of living
and non-living matter may be left to the arbitrament of time. For
practical purposes a decision one way or the other makes very little
difference to the course of biological enquiry. The fundamental unity
of scientific method in chemistry and physics is not invalidated by
the fact that some phenomena can only be dealt with successfully in
thermodynamical terms, while yet others yield only to treatment with
the aid of kinetic and molecular hypotheses. It is less important to
know how far the properties of living matter can be reduced to physical
chemistry than to decide whether the logical structure of biological
enquiry is essentially similar to or different from that of physical
science. This is an issue of the most far-reaching consequences, not
merely for philosophy but for biology as well. Though rarely stated
explicitly, it represents the basic divergence of standpoint between
the mechanist and the vitalist or holist. It is not merely a matter of
taste or temperament: it is profoundly relevant to the way in which
biological enquiry continues to develop. In this matter scepticism can
only be justified by disinclination to face uncomfortable conclusions.
If the logical structure of biological enquiry is essentially similar
to that of physical science, we must entertain the possibility of
interpreting the whole domain of living matter without departing
from the principle of ethical neutrality. This is not a pleasant
possibility to admit; and it is hardly surprising that few biologists
are enthusiastic in committing themselves with regard to it. If we
find that there is no fundamental difference between the logical
structure of biological and physical science, we cannot follow Dr.
Whitehead in reviving the hope that scientific enquiry will eventually
yield conclusions about the universe in conformity with our ethical
predilections. If, without modifying the structure of its logic,
biological science is capable of annexing as its parish the entire
survey of living matter, there remains no nicely defined boundary
at which science ends and philosophy begins. Philosophical enquiry
must then abandon its pretensions to arrive at conclusions about
the universe unaided by scientific discovery. It must restrict its
operations to an examination of the logical structure of beliefs. It is
therefore remarkable that the biological standpoint has been so little
explored in contemporary criticism of traditional philosophy.
During the past two decades there have been three outstanding
developments in biological research, the work of A. V. Hill and
Meyerhof on the chemical mechanics of muscle, the extension of Mendel’s
hypothesis by Morgan and his colleagues at Columbia, and the study of
the conditioned reflex by Pavlov’s school. Of these the first alone
represents an advance in the actual reduction of vital processes to
physical chemistry. Yet no aspect of biology could be selected more
appropriately than Morgan’s hypothesis to illustrate its logical unity
with the study of chemistry. The study of the conditioned reflex
has not as yet enlisted the resources of physical chemistry to any
noticeable extent. Nor does it employ a logical technique as elaborate
as that of the modern chromosome hypothesis. Its importance lies in
the fact that it has emancipated biological study from the Cartesian
dualism with its implicit assumption that method of enquiry applicable
to one aspect of the properties of living matter is of a totally
different kind from that employed in dealing with the remainder.
To estimate the significance of this advance it is necessary to start
with a clear statement about the meaning of a word. The term _reflex_
is used by dentists, politicians and faith healers with a variety of
implications irrelevant to the biologist. To exclude these irrelevant
associations it is best to be concrete. Suppose that we decapitate
or destroy the brain of a frog, and suspend it, legs downwards, in a
vertical position. On raising a vessel of warm--about 40° C.--water,
until the tips of the toes touch the surface, the legs of the animal
are withdrawn after a short interval. This event takes place regularly
and similarly under the same conditions. It is as definite and
predictable a property of secular objects as is the precipitation of
barium sulphate on mixing a solution of barium chloride with a solution
of sodium sulphate. It is, if you care to express it in that way, a
physical reaction between warm water and frog toes. In biological
nomenclature it is a reflex.
The word reflex is not used in biology to denote every change that
occurs in living matter. To clarify its meaning further we must
consider how such a phenomenon can be studied more intimately. To the
biologist it presents two types of problem. One is that of analysing
the constituent parts of the reaction, and is analogous to what the
chemist does, when he determines the solubility and dissociation
constants of barium sulphate, barium chloride, sodium sulphate and
sodium chloride to define more precisely what occurs during the
reaction with a view to elucidating conditions under which it may be
expected to occur. In the biological example that we have taken the
first stage involves the purely spatial (or anatomical) examination of
the reaction. It may be noted in this connexion that anatomy in its
initial phase was an experimental science, and only became a catalogue
in its dotage. We observe that we are dealing with a localized response
to a localized agent involving a spatially localized structure the
nervous system. We can in fact obtain the reaction from a preparation
from which every structure but the skin of the toe, the nervous system
and the muscles of the leg have been removed. From this point we
proceed by a study of the temporal relations of the phenomenon, first
undertaken by Helmholtz, to show that a disturbance is propagated
at a measurable, predictable and modifiable rate from the seat of
application of the agent to the seat of the visible reaction. The
further analysis of the problem from the physico-chemical standpoint,
an essentially modern development, will be referred to in a subsequent
essay. We have now obtained the current definition of a reflex as a
localized response to a localized stimulus, involving the intervention
of the propagated disturbance known as the _nervous impulse_. Erroneous
ideas implied in the common use of the term reflex arise chiefly in
connexion with the second aspect of the study of reflex phenomena. This
is not readily comparable with the investigation of a simple reaction
like the precipitation of barium chloride. It might be compared with
the interpretation of a more complex system such as the oxidation of
oxalic acid in the presence of potassium permanganate and sulphuric
acid, when the behaviour of any two reactants towards one another is
already known. Frogs lift their legs from time to time in civil life,
when they enjoy the use of a head. We may therefore ask what part
do such reflexes, as we can study in the headless frog, play in the
behaviour of the intact animal.
In any reflex displayed by the pithed frog the nervous impulse
traverses a characteristic path. From the skin, the receptive area
affected, it passes by one of numerous fibres of microscopic thickness
to the spinal cord. Such fibres together with others carrying impulses
from the cord to the muscles or glands collectively constitute the
visible nerves. Fibres carrying impulses into the cord divide into very
fine branches in the inner core or grey matter. These fine branches
are intertwined with the ramifications of other fibres passing up
and down the length of the cord. The latter branch at their other
extremities around the fine endings of fibres which pass from the cord
to the glands and muscles. An impulse entering the spinal cord first
therefore passes across the junction or _synapse_ between the fibre
along which it enters the cord and some other fibre running up or down
the cord. Having traversed the latter, it passes across the junction or
synapse between its branched ending and that of some fibre connecting
the spinal cord with a muscle or gland. Reflex action depends upon the
fact that an impulse travelling along a particular fibre can traverse
some synapses more readily than others. This is a physical process,
occupying a measurable time. By the use of certain physical reagents it
is possible to increase the conductivity of the synapses, so that an
impulse entering the cord irradiates to all the muscles of the body.
Strychnine is such a reagent.
The familiar fact that the moth flies towards the candle will serve
to illustrate how the study of a simple reflex, like the withdrawal
of the toes of the pithed frog from warm water, makes it possible to
make predictable conclusions about the normal behaviour of animals.
If the nerves of the frog’s leg are severed, the leg hangs limply.
Normally the muscles of the leg are never completely relaxed. They
are maintained in a state of partial contraction or _tone_, reflexly
determined by a number of agencies which for our present purpose it
is unnecessary to specify. The nerve fibres which run up and down the
length of the spinal cord in the frog cross from one side to the other
at some level, and on this account most reflexes obtained in the pithed
frog, when only one side is stimulated, involve muscular response of
both sides of the body. Insects which move towards the light become
noticeably more limp in darkness. Light reflexly increases the tone of
their muscles. In insects there is little crossing of fibres from one
side of the central nervous system to the other. It follows that, if
light reflexly increases tone, the muscles of that side will be more
contracted, when one eye is illuminated more strongly than its fellow.
This will have the effect of bending the body round in the direction of
the incident beam, until the head is brought into such a position that
both sides are equally illuminated. Having attained this position the
body will continue to move along the direction of the incident beam. If
it swerves to the right or left, it is automatically readjusted.
This interpretation of the proverbial flight of the moth towards the
candle permits us to make a very large number of easily verifiable
predictions. One simple consequence repeatedly confirmed by experiment
on a variety of insects which fly towards the light is the fact that,
when one eye is blinded, they fly in circles. There is no need to
mention the variety of predictable positions which such insects occupy,
when allowed to crawl up rotating cylinders illuminated in various
ways. One other rather interesting result of the experimental analysis
of this phenomenon is worth mentioning. According to the common sense
view the insect moves towards the candle, because it likes the
light. There is one and only one fairly evident inference from the
teleological way of looking at the matter. It implies that the moth
should always fly from the darker to the brighter situation. Now the
interpretation of its movement in terms of reflex action signifies that
it is the direction of the light rays and not primarily the intensity
of illumination which determines the direction of its movement. In
Nature moving along the direction of the rays towards the source of
light usually involves progression from a darker to a brighter region.
In the laboratory it is easy to arrange conditions so that an insect
crawling along the direction of an obliquely incident beam, moves from
a brighter to a darker area, as it approaches the source. In doing so
it behaves, as it would be predicted to behave in such a situation
on the assumption that its behaviour is determined by reflex action.
According to the teleological view it should do the opposite.
Even in the behaviour of so capricious an animal as man himself, it
is possible to isolate units of behaviour to which the term _reflex_
is appropriate. The entire behaviour of a pithed frog or of a dog
deprived of its brain can be regarded as the summation of a number
of discrete reflexes compounded according to ascertainable laws. The
problem is not a simple one; but the way in which the operation of
one reflex affects the exercise of another has been elucidated with
considerable success by Sherrington and his co-workers. Sherrington has
paid special attention to what occurs in the simultaneous application
of two stimuli whose appropriate responses involve the propagation
of impulses along common fibres within the central nervous system.
A further complication is introduced by the existence of inhibitory
reflexes, responses which involve the cessation or the diminution of
activity already in progress before the application of the stimulus.
The work of Magnus and his colleagues, who have solved the riddle of
how a cat falls on all fours, demonstrates to a very large extent the
possibility of interpreting balancing movements of the body as the
summation of such reflexes as are readily exhibited in the brainless
or “spinal” animal. Yet few physiologists have ventured to entertain
the likelihood that the entire behaviour of even such an animal as a
cat, still less man himself, could be treated successfully in this
way. Hence has arisen the traditional distinction between reflex and
voluntary activity. So long as that distinction was a valid one,
biology admitted a fundamental dualism in its subject matter and in its
method. The vitalist was in a position to claim that there is a group
of properties of living matter in dealing with which we must adopt
introspective rather than physical methods of enquiry. The mechanist
might reply epigrammatically that physiology deals with what we know
about the central nervous system, psychology with what we do not know.
The distinction still remained.
There are certain fairly evident reasons why the behaviour of a frog
deprived of its brain should be simpler than that of the intact animal.
One is that the number of possible paths along which nervous impulses
can pass is much smaller. Another is the fact that the brain receives
the nerves which bring in impulses from the three great receptor
organs, or, in the older terminology, sense organs of the head. The eye
and the ear bring the organism within the range of physical influence
of innumerable events remotely situated in space. When we have allowed
for all such differences there remains a perfectly tangible distinction
between the behaviour of the spinal and that of the intact animal.
The response that we have hitherto called a reflex is such that for a
given agency under the same external conditions we may expect the same
result. There are the best of reasons, based not on any introspective
ideas but upon the study of behaviour to make us think that however
much we standardize the external conditions at the moment, when the
stimulus is applied, we can never predict from that alone exactly
what will happen as the result of the application of certain types of
stimuli. The performance of “learning” justifies this conclusion, and
it has been customary in the past to refer this property of living
matter to essentially non-physical concepts such as _memory_. By
defining in this way the distinction between reflex behaviour in the
traditional sense and voluntary or conscious behaviour, a new problem
has emerged. This may be stated in the following way. If instead of
concentrating exclusively on what is happening at the moment, we take
into consideration the way in which a given stimulus has been presented
to an organism on previous occasions, is it possible to establish any
relation between the effect it now produces and the events associated
with its application antecedently? In so stating the issue we have
introduced no new and introspective concepts foreign to the traditional
physiology of the reflex. We have simply envisaged the possibility of
studying conditions under which new reflex systems may be brought into
being.
§2
It is this problem which the Russian physiologist Pavlov and his
co-workers have attacked with such conspicuous success during the
past two decades. For some time their researches remained little known
in this country, but two translations of Pavlov’s lectures are now
accessible to the English-speaking reader. There is therefore no need
to go into details concerning the experimental technique which is
formidable. The more significant developments of the subject may be
dealt with by considering how aspects of behaviour which were formerly
referred to the introspective concepts of memory, attention and
sensation can now be investigated without departing from the language
adopted by physiologists, when describing the properties of simple
reflex action.
Pavlov’s investigations commenced with the study of salivary secretion
in dogs. A dog which has been deprived of the forebrain secretes
saliva, when food is introduced into the mouth. The intact animal also
secretes saliva, when food is brought within the range of its eyes or
nostrils. In the adult the sight or smell of food is an appropriate
stimulus for reflex salivary secretion. The ringing of a bell is
ordinarily without effect on the secretion of saliva; but the ringing
of a bell if repeated a certain number of times, when food is also
presented, eventually comes to evoke salivary secretion, when food
does not accompany it. In general it is found that, in the intact
animal, a previously indifferent stimulus applied at suitable intervals
simultaneously with the application of a stimulus which unconditionally
evokes a reflex response is found to acquire the property of evoking
the same reflex response, when unaccompanied by the original or
“unconditioned” stimulus. A new reflex has been built up. Such reflexes
are called by Pavlov _conditioned_ reflexes, and the previously
indifferent stimulus is called the conditioned stimulus. Any event in
the external world which affects a receptor organ may in the intact
animal become a conditioned stimulus, provided external conditions
are rigidly standardized in other respects, provided also that it
accompanies the unconditioned stimulus a sufficient number of times
depending on whether the application is precisely simultaneous, whether
the conditioned stimulus begins to operate before the unconditioned,
overlapping it in duration or separated from it by a short interval.
The task of defining the facility with which a conditioned reflex is
built up involves a study of the significance of the interval between
successive applications of both stimuli and of the juxtaposition of
conditioned and unconditioned stimulus. In defining the conditions
which determine the bringing into being of a new reflex system by this
method, we are investigating a class of phenomena which would formerly
have been attributed to “memory.” At no point is it necessary to depart
from the conventions of scientific nomenclature; and in place of a
descriptive epithet, we arrive at a definite specification regarding
when and whether an event will occur.
What it has been the custom to denote by the term memory is only one
aspect of the problem of “conscious” or “voluntary” behaviour, that
is to say those aspects of behaviour which are spatially referable to
reflex paths in the fore brain. An animal is constantly subject to
the simultaneous application of many indifferent and unconditioned
stimuli, but its behaviour is selective. This introduces the problem
of _attention_. To ascertain the conditions which prevent new reflex
systems from coming into being, or extinguish them when they have
become established, was perhaps the most important aspect of Pavlov’s
work, because an understanding of this part of the problem underlies
the successful control of experimental procedure. The possibility of
isolating a conditioned reflex for study implies the existence of
some inhibitory agencies which prevent the normal surroundings of the
laboratory from exerting a significant influence on the course of
the experiment. The inhibition of conditioned reflexes is a complex
question; and its complexity emphasizes how broad a basis they offer
for the interpretation of “conscious” behaviour in general and the
interpretation of _attention_ in particular.
From this standpoint two important types of inhibition are called
by Pavlov inhibition by extinction and conditional inhibition. The
first term refers to the fact that, when an indifferent stimulus has
been converted into a conditioned stimulus, and is then allowed to
act repeatedly without the unconditioned stimulus, it gradually loses
its potency, regaining it after an interval of rest. Conditional
inhibition is the extinction which occurs, when a new indifferent
stimulus is superimposed upon the effective phase of a conditioned
stimulus. A third and especially important form of inhibition is the
extinction of a state of inhibition by conditional inhibition, or as
Pavlov calls it, inhibition of inhibition. Let us suppose that an
organ note of one thousand vibrations per second has been made the
signal for salivary secretion by repeated application of the stimulus,
when food is administered to the animal. If it is now administered
repeatedly without the accompaniment of food, it suffers inhibition
by extinction, but recovers its efficacy after a period of rest. If,
during the indifferent period, the experimenter superimposes on the
now ineffective sound stimulus another indifferent agent such as the
flash of a lamp before the dog’s eyes, secretion of saliva ensues.
The sound regains its efficacy as a conditioned stimulus. One other
type of inhibition which can be studied experimentally is “generalized
inhibition” or elimination of the activity of the fore brain, which can
be brought about in the dog by local warming or cooling of an area of
the skin. This has an intimate bearing on the phenomena of sleep and
hypnotic trance, as also on the advantages of summer time.
Perhaps the most radical consequence of the line of work which we
are now considering lies in the possibilities which it presents for
inverting our traditional attitude to the discussion of “sensation.”
When we can isolate some simple unconditioned response to a particular
stimulus, we can investigate the extent to which the efficacy of
the stimulus is localized with reference to some receptive area,
and discuss the sense organ in the same way as a piece of physical
apparatus. We know for instance that a frog does not respond to white
or black background by the appropriate change in colour of the skin, if
its eyes are removed. The influence of the earth’s gravitational field
on the way in which a frog maintains its normal balance in swimming
provides another illustration of the way in which the experimental
biologist deals with the phenomenon of receptivity, when it is possible
to isolate a type of response which invariably accompanies a particular
type of stimulation. In this instance the receptor is that part of the
internal ear known as the labyrinthine organ. After destruction of the
labyrinthine organ on one side only, a frog swims in a spiral path. If
the internal ear of both sides is removed, it swims hither and thither,
as likely as not upside down or sideways without any sign of its normal
maintenance of balance. The inner ear of the frog or man with its
three semicircular canals in the three Cartesian planes is a rather
elaborate example of a type of receptor organ represented in shrimps
by two little sacs called statocysts at the base of the feelers.
These sacs contain concretions of sand known as the statoliths.
Experimentally the sand can be replaced by iron filings. If this is
done, the shrimp swims upside down, when a strong electromagnet is
placed above it. The position occupied by the statolith in its sac is
determined by the pull of gravity in ordinary circumstances. When the
body is bent, the statocyst comes into contact with a new portion of
the wall of the sac, thus stimulating a different set of nerve fibres,
and initiating appropriate muscular reflexes. The balancing movements
of a shrimp in swimming also depend on the eyes. With both feelers
removed a shrimp swims normally in daylight. It loses its balance
completely in a dark room; and swims on its back if illuminated from
below. Removal of one eye or one statocyst does not affect its balance
in daylight, unless the two operations are performed on the same
animal. It then swims in spirals.
A modern biologist adopts to the statocyst and the eye the same
attitude which he would adopt to the self starter of a motor car, if he
were quite ignorant of its mechanism. Sometimes his problem is further
complicated by the necessity of turning on the switch before the engine
will start, adjusting the spark or cutting down the air. In an animal
whose behaviour is largely conditioned behaviour, it is not so easy to
isolate simple invariable responses to particular types of external
agency. We lapse into the language of introspective psychology. Pavlov
has shown that this is unnecessary. By employing the method of building
up conditioned reflexes to define the limits of discrimination, the
analysis of sensation can be carried out without departing from the
attitude which we adopt to a motor car. Let us suppose that the sound
of a tuning fork of 256 vibrations per second, i.e. middle C, is
accompanied by electrical stimulation of the paw of the dog, until the
note itself becomes an effective stimulus for withdrawal of the paw.
A tuning fork of 264 vibrations will also evoke the withdrawal of the
paw; but the application of the second stimulus suffers inhibition by
extinction before the original (middle C), as can be shown by applying
the latter after response to the tuning fork of 264 vibrations has
been extinguished. Applying series of tuning forks in such experiments
it is found that the limits of discrimination in dogs is a fraction
of a tone. The delicacy of this method of testing discrimination or
selective receptivity to a given range of stimuli depends on the fact
that it is possible not merely to show whether one stimulus can be
substituted for another in a conditioned reflex but to measure the
extent to which a given stimulus can replace another. Judged from this
standpoint dogs and cats are colour blind, as far as such a statement
can have any tangible meaning. That is to say, differences of light
intensity but not of wave length in the effective range determine the
reactions of these animals to photic stimuli.
§3
In the light of Pavlov’s work the problem of conscious behaviour, or
as we should now say conditioned behaviour, no longer presents itself
to biological enquiry as a domain in which the methods of traditional
physiology must be abandoned in favour of introspective speculation.
It becomes the problem of defining how new reflex systems can be
built up. The possibility of a further analysis of the process on
mechanistic lines will be discussed elsewhere. Whatever success attends
such an attempt, the fact remains that the controversy between the
mechanistic and vitalistic schools must now be conducted on a new
basis. Mechanistic biology could not claim to take a comprehensive view
of the properties of living matter, so long as it failed to indicate
how “voluntary” activity, as it was almost universally denoted by
physiologists, differs from reflex activity. It is true that some of
the more radical mechanists like Loeb preferred to speak of associative
behaviour as having a more objective flavour. But Loeb’s own use of the
concept of “brain images” emphasizes how fundamental is the innovation
which the work of Pavlov’s school has introduced into philosophical
discussion. The mechanist never legitimately claimed more than the
right to investigate the properties of living matter in its simpler
manifestations by those methods whose success had been justified in
the domain of physics and chemistry. If the mechanist ventured to
speculate beyond those limits he transgressed his terms of reference.
Until the publication of the work of Pavlov’s school physiology was
tied hand and foot to the traditional distinction between reflex and
voluntary behaviour. Thus the author of a standard work on human
physiology with a distinctly mechanistic tendency writes on the
functions of the cerebellum: “... the degree of consciousness, if any,
exhibited by the cerebellum is of a much lower order than that shown
by the cerebrum. All observers agree that there is no apparent loss of
sensation after removal of the cerebellum, but Luciani, Russell and
others state their belief that in some indefinable way it is affected
by such operations. Whatever functions of this kind are present we can
define only by the unsatisfactory terms of subconscious rather than
unconscious...” What Howell wrote in 1905 might have been written by
any mechanist of that period. The physiologist inevitably lapsed into
introspective terminology, when dealing with brain physiology; and it
is this restricted mechanistic outlook which Dr. Haldane has attacked
in his recent Gifford Lectures. It is not difficult to show that the
mechanist, as that term is used by Dr. Haldane, accepted implicitly the
Cartesian compromise. It is surprising that, although Pavlov’s work
has been generally accepted by contemporary biologists, Dr. Haldane
completely refrains from considering its bearing on the present status
of the mechanistic conception of life.
Dr. Haldane’s statement that the method of traditional, i.e.
mechanistic, physiology “tells us nothing, however far we may extend
it, regarding the distinctive characters of conscious behaviour” is
especially remarkable. Although few writers have hitherto ventured to
formulate the far-reaching philosophical consequences of Pavlov’s work,
more than fifteen years have passed since the veteran physiologist Sir
William Bayliss made the following pronouncement:
“Pavlov states that he was struck by the fact that when the
physiologist leaves the study of the simpler parts of the central
nervous system which he has investigated by the observation of
reflexes, and proceeds to the higher parts, his methods suddenly
change. He gives up the observation of the relation between
external phenomena and the reaction of the organism to them and
introduces psychological ideas, derived from his own internal
consciousness. To extend to the higher centres the method of
observing what changes in the organism are correlated with external
changes might appear too difficult, but Pavlov has succeeded in
doing so to a remarkable degree” (_General Principles_, 1914, p.
502).
In denouncing the mechanistic view of life as set forth by Professor
Donnan at the meeting of the British Association in 1928, Dr. Haldane
states:
“I regard this view as now entirely obsolete, since it ignores
the facts, and this is far more evident now than it was a few
years ago, before physiology had become to so large an extent a
_quantitative science_” (italics inserted) “... The fact that
Professor Donnan, though his work in physical chemistry commands
universal respect among those who know it, is not a physiologist,
may partly account for his opinions.”
Perhaps also the fact that Dr. Haldane, whose work on the physiology
of respiration and excretion commands universal respect among those
who know it, neglects in his Gifford Lectures to make any reference to
the work of Pavlov may partly account for his belief that “a biologist
interprets his observations in a different manner from a physicist”
(p. 97). It is certainly permissible to state that Dr. Haldane is not
speaking for biologists as a whole, when he denies that the problem
of conscious behaviour can ever be attacked successfully by the
traditional method of the physiologist.
Biologists may be expected to differ in the hopes they may entertain
as to the progress of further investigation. We can at least envisage
the possibility that biology will advance towards a comprehensive
account of the properties of living matter without interpreting its
observations in a manner different from that adopted in physics. The
work of Pavlov’s school shows that it is not necessary to introduce
concepts foreign to other parts of biology in dealing with conscious
behaviour. Of late years the notion of matter which is so fundamental
to common sense has been disintegrated by the advance of the physical
sciences. The notion of mind or consciousness so fundamental to common
sense is being disintegrated by contemporary biology in an analogous
way. If materialism in the traditional sense is dead, idealism in
its traditional form is dead. Like traditional dualism they are dead
because they never contained within themselves the capacity for
growth. The success of biology in attacking the problem of “conscious
behaviour” in Haldane’s terminology has been consistent with the
attitude of treating _conditioned behaviour_ as an aspect of the
properties of a peculiar kind of matter, living matter. In that sense
the new philosophical outlook which emerges from Pavlov’s work is a
materialistic one.
Physiology has at length discovered a neutral ground for the
investigation of the problem of learning. If it is too early to
predict the final outcome of this advance, it is permissible to
proffer some tentative suggestions concerning its influence on the
future of philosophical discussion. From Plato to modern times
philosophical enquiry has mainly occupied itself with what Kant calls
“the problems of mere pure reason.” Of these Kant enumerates God,
Freedom and Immortality as the three principal objects of philosophical
enquiry. For the final solution of these problems, Kant asserted that
“philosophy stands in need of a science which shall determine the
possibility, principles and extent of human knowledge _a priori_.”
Introspective psychology was the “science” to which he assigned this
task. Introspective psychology has failed to fulfil the expectations
which Kant entertained, when he concluded the _Critique_ by expressing
the hope that it “would bring reason to perfect contentment in
regard to that which has always, but without permanent results,
occupied her powers and engaged her ardent desire for knowledge.”
The type of psychology which Kant promoted had already begun to
sever its connexion with moral philosophy before the emergence of
the Behaviourist tendency in an explicit form. Kant did not refute
Hume’s arguments when he proposed the question, “whence could our
experience acquire certainty, if all the rules on which it depends were
themselves empirical and fortuitous”? He stated a problem. For its
solution he lacked a method. For its discussion he lacked a vocabulary.
If the physiology of human learning continues to progress under the
Behaviourist influence to which Pavlov’s work has given birth, Kant’s
solution of the problem, which he himself propounded, must eventually
be relegated to the same status as astrology and palmistry in the
history of human knowledge.
The strength of Kant’s case against Hume’s empiricism lay in the
immature state of physiological knowledge, when the _Critique of
Pure Reason_ was published. Kant’s views on Space and Time were
circumscribed by the biological limitations of his period. The Kantian
conception of experience was defined by the influence of light, sound,
chemical stimuli, mechanical pressure and temperature affecting the
eye, the ear, the nose, the mouth and the skin--the only receptor
organs recognized by the physiologists of the eighteenth century. Two
of the most important instruments of receptivity in the human body, the
labyrinthine organ and the proprioceptors which respond to the state
of tone of the muscles, were not studied till the nineteenth century.
If Kant had been familiar with the physiology of the labyrinthine
organ, he would not have argued with the same cogency that the concept
of space is essentially different from the concept of weight. The
_a priori_ necessity of the proposition that “space has only three
dimensions” was determined, according to Kant, by the existence of an
“external sense” which is “a property of the mind.” If he had lived
fifty years later he would have realized that the “necessity” of the
Cartesian frame work is a material consequence of the structure of the
internal ear. If Kant had been familiar with Sherrington’s work on
the proprioceptor organs, he would have seen a deeper significance in
the experiment which Galileo performed, when he used his own pulse to
measure the period of a swinging lamp. Kant was compelled to attribute
the “_a priori_ necessity” of the proposition that “time has only
one dimension” to “the internal sense by which the mind contemplates
itself.” The time conditioned reflexes which Pavlov has demonstrated
are intelligible to modern physiology without recourse to a “faculty
of pure _a priori_ cognition.” The human body is itself a clock from
whose tickings we can never escape. Periodic changes in tone of the
body muscles influence the proprioceptor organs in a manner essentially
analogous to the way in which light exerts its effect on the eye.[2]
Kant’s physiology calls for more detailed treatment elsewhere. In
concluding this essay, I must remove one source of misunderstanding. I
do not assert that all aspects of conscious behaviour will eventually
be explained in terms of Pavlov’s conditioned reflexes. I do affirm
that Pavlov has successfully applied the methods of traditional
physiology to the study of processes presumably included in Dr.
Haldane’s definition of conscious behaviour. The strength of Dr.
Haldane’s position lies in the fact that behaviour ceases to be called
conscious so soon as it is possible to bring it within the range of
scientific prediction. I can well believe that the vitalists of fifty
years hence will be assuring their opponents that they never regarded
the process of learning, the phenomenon of attention or sensory
discrimination as characteristics of the conscious state.
II. THE ATOMISTIC VIEW OF PARENTHOOD
“When you can measure what you are talking about, and express
it in numbers, you know something about it; but when you cannot
measure it, when you cannot express it in numbers, your knowledge
is of a meagre and unsatisfactory kind; it may be the beginning
of knowledge, but you have scarcely in your thoughts advanced to
the stage of science whatever the matter may be...”--Lord Kelvin,
_Addresses_
§1
The future progress of biological science depends upon a large number
of unpredictable contingencies, some political, others meteorological.
The collision of the earth with a comet may leave the fate of the
argument between the mechanist and the vitalist for ever unsettled.
There is therefore no justification for a dogmatic assertion that
all the properties of living matter will eventually be reduced to
the same hypotheses as are adopted in physical chemistry. But it is
doubtful whether any biologists of the mechanistic persuasion have on
any occasion explicitly committed themselves to so rash a statement.
The vitalistic Sarah Gamp has invented a mechanistic Mrs. Harris with
the express object of giving her a piece of her mind. As a polemical
device this is most valuable, especially in political propaganda. It
does not help the mechanist to understand what vitalism can offer as a
guide to further biological enquiry. His perplexity is increased by the
circumstance that so many vitalists of the platform behave themselves
with mechanistic propriety in the laboratory. Dogmatism is at least as
frequent among those who call themselves vitalists as among mechanists.
The vitalist does not qualify his denial that a complete solution
of the riddle of life can be obtained in physico-chemical terms. The
mechanist is usually content to state that he knows of no other terms
in which an intelligible solution could be found. The vitalist even
goes further, and, quite inconsistently with his laboratory practice,
if he is a competent biologist, asserts, that in its very methodology,
biology is an _independent_ science. A biologist, says Dr. Haldane
in his Gifford Lectures, “interprets his observations in a different
manner from that of the physicist.”
This I think is the main bone of contention between the two attitudes
which are generically denoted by the terms mechanistic and vitalistic.
The real issue has shifted from deciding whether the hypotheses
of physics and chemistry suffice for the interpretation of vital
phenomena to deciding whether there is an essential difference between
the logical structure of those branches of science that deal with
living matter and those which deal with inanimate objects. This is a
welcome change, because it presents a much more genuine and concrete
problem for solution. It is somewhat surprising that the controversy
should undergo such a metamorphosis at the present moment. The recent
development of evolutionary biology is especially calculated to
reinforce the belief that biological theory only progresses, when the
biologist adopts towards the subject matter of his investigations the
same attitude as that which the chemist and physicist adopt towards the
objects which they study. In our generation it is possible to find in
those aspects of biology which are most recalcitrant to the application
of physico-chemical hypotheses the most conspicuous examples of a
fundamental similarity in the logical procedure which the biologist
on the one hand and the physicist or chemist on the other employ in
constructing their hypotheses. It would not be possible to select from
the whole field of biological science a more striking illustration of
the success of quantitative and experimental methods than the recent
extension of Mendel’s hypothesis by Morgan’s school. This advance
has entailed an extensive elimination of teleological concepts in
the interpretation of the evolutionary process. Yet the phenomena of
heredity and variation at present lie completely outside the scope of
physico-chemical analysis in the ordinary sense of the term; and any
attempt to formulate the problems of genetics in physico-chemical terms
is still a matter of pure conjecture.
In this sense we may agree with one writer of the vitalistic school in
saying that to speak of the “mechanism of heredity” is a meaningless
collocation of words. But if our interest is primarily directed not
to the end product itself but towards the way in which the scientist
proceeds to elaborate his hypotheses, the study of heredity provides
a particularly clear example of how a hypothesis developed without
any departure from the _principle of mechanism_ can yield verifiable
conclusions about the behaviour of living systems. From this point of
view it is both legitimate and intelligible to speak of the mechanisms
of heredity and variation; and the expression is as permissible as the
analogous phrase, the mechanism of chemical reaction. A comparison
of the growth of the Mendelian principle with Dalton’s atomic theory
of the structure of matter will help us to see whether the biologist
does actually interpret his observations in a manner different from
that adopted by the student of non-living matter, and whether the
biologist has recourse to a kind of logic which is different from
the logic which the physicist and chemist employ in framing their own
generalizations.
When Mendel took up the problem of hybridization, the nature of
fertilization in plants was known in a general way. Just a century
before Mendel began his work Kolreuter by painting pollen from one
individual on to the stigmas of another variety, and vice versa, had
shown that hybrids inherit equally from the pollen and seed plant. At
the end of the eighteenth century and the beginning of the nineteenth,
Knight and Goss in England had made further progress in crossing pure
bred varieties by calling attention to the “splitting” of hybrids, or
reappearance of parental types when intercrossing hybrid offspring.
Contemporaneously with Mendel, Naudin in France studied this phenomenon
more closely, and came very near to formulating Mendel’s principle.
His results were published in 1862. These pioneers in hybridization
laid down the necessity of working with what to the geneticist is like
pure chemicals to the chemist, pure breeding stock. They fell short of
arriving at far-reaching results, because their attitude to heredity
was dominated by the holistic standpoint. They could only think of
the plant in terms of a preconceived notion of individuality. They
refrained from focusing their attention on the separate parts, and
following out the fate of discrete characteristics in their crosses.
We must not overlook the debt which Mendel owed to the pioneers of
hybridization. There would have been no modern chemistry if the
Arabs and alchemists had not devoted years of laborious study to the
clarification of our idea of a pure substance; and there would have
been no genetics, if the idea of pure breeding stock had not been laid
down by Mendel’s predecessors. Chemistry failed to progress beyond
the stage of describing new compounds so long as it remained entangled
in the vitalistic “phlogiston” concept; and genetics, the study of
heredity and variation, remained purely descriptive, until it was
emancipated by Mendel from the holistic tendency to concentrate upon
the organism as a whole. Naudin did in fact envisage less definitely
than Mendel the atomistic concept of heredity, just as William Higgins
had partly visualized the chemical possibilities of atoms before Dalton
published his theory.
Mendel used in his researches pure breeding stocks differing only in
well-defined particulars, employing single characteristics as units
of study, and recording the progeny of every cross separately for
comparative observation. In his original work Mendel chiefly dealt
with the common pea, which possesses two advantages which recommend
it for such experimentation, namely, that its flowers are capable
of self fertilization (i.e., the pistil can be pollinated from the
stamens of the same flower) and that it has a number of well-marked
varieties distinguished by tangible characteristics such as the shape
(round or wrinkled) and colour (green or yellow) of the seeds, or the
stature (tall or dwarf) of the shoot, etc. In all his crosses involving
a single difference of this kind he found that the first generation
of the cross resembled one of the parents. When these crossbreeds
were self fertilized, they produced offspring resembling the original
parents in the constant ratio of three to one. One-quarter of the
offspring of the crossbreeds resembled one parent and bred true;
one-quarter resembled the other parent and bred true; and the remaining
half being like the “dominant” parent, which the first generation
of hybrids resembled, behaved exactly like the latter, when self
fertilized.
An investigator who had not the attitude which makes a capable chemist
might have been distracted by the peculiar circumstance of dominance,
or the resemblance of the impure individuals to one of the parents
exclusively. Mendel rightly judged this to be insignificant. A chemical
analogy will perhaps assist to make this clear. Sodium and potassium
yield colourless salts with most common acids, but the permanganates
of both are purple in solution. The salts of copper are generally of
a bluish or greenish tint in solution. In the one case the anion, in
the other case the kation, is the dominant factor in determining the
physical property of colour; but in both cases the other component
behaves in any reaction with no less characteristic efficacy, because
its presence is seemingly masked. So likewise Mendel looked beyond the
bodily resemblance of the dominant parental and hybrid individuals
to their hereditary makeup; and recognized in his experimental data
two general conclusions which prompted special consideration. One
was the fact that the original parental types can be recovered in
all their purity. The other was the fact that the various hereditary
types produced by hybridization regularly appear in the same numerical
ratios. Both conclusions are of universal validity, though Mendel had
the very good fortune to select materials which yield the simplest
type of numerical results which occur in crosses between pure strains.
When Dalton formulated the atomic hypothesis two fundamental empirical
generalisations of chemistry were fully accredited. The law of the
conservation of matter and the law of constant proportions had been
established. Mendel found in his data the proof of what we might call
the principle of the conservation of genetic materials and the law of
constant genetic proportions. To the recognition of these empirical
generalizations he added a conceptualization of the basis of their
existence in terms of discrete factors. These factors were according
to Mendel’s hypothesis (or Mendel’s “first law”) units of hereditary
combination, just as Dalton’s atoms were units of chemical combination.
Each character involved in his crosses was regarded by Mendel as
determined by a factor derived from the maternal and one derived from
the paternal parent. A pure individual was thus represented by _aa_
or _bb_, and an impure individual by _ab_. Mendel assumed that _a_
and _b_ are atoms of heredity in the sense that they retain their
separate entities through the whole course of development. Having
introduced this conception, he showed that all his numerical data
followed from the laws of chance, if the maternal and paternal factors
which determine a particular character separate in the formation
of the gametes (pollen and ovules) so that one-half of the gametes
contain only the maternal and one-half only the paternal factor for the
character considered. The combinations which may occur as the result of
fertilization are compatible with the assumption that any given male
gamete (pollen or sperm) may fertilize any given female gamete (ovule
or egg cell). Mendel’s first law may then be stated thus: characters
distinguishing different hereditary strains depend upon factors which
are inherited from both parents and _segregate_ in the formation of
the gametes, so that one-half contain the paternal and one-half the
maternal factor. Mendel tested the implications of this hypothesis by
crossing his hybrids to pure types with verifiable results. He then
proceeded to make crosses involving two or three character differences.
This led him to enunciate a second law which might be compared with the
law of multiple proportions in chemistry, for its validity is of less
general significance than the first law. It served eventually to direct
attention to the much more complicated numerical results which arise in
dealing with character differences attributable not to one but several
pairs of factors. The analysis of such cases was left to Mendel’s
successors.
There is internal evidence in Mendel’s writings to support the
view that Mendel himself realized that the atomistic conception of
inheritance would demand a drastic revision of the prevailing notion
of variation. To Mendel’s generation, to Darwin and the pioneers of
Natural Selection, variation and heredity were co-extensive terms.
Offspring were always on the whole like their parents, but always on
the other hand a little different. So the species in conformity with
sound liberal principles broadened down from precedent to precedent.
But on the atomistic view heredity is essentially conservative, and
variation essentially revolutionary. For an indefinite number of
generations the atoms of heredity remain unchanged. But times come,
when the political barometer falls, and the change when it happens is
a discontinuous one. Something new has been brought into being, as
when lead is produced from the disintegration of radium or another
allotropic modification of an element is formed. The full implications
of this were not destined to be realized till forty years had elapsed.
Meanwhile the evolutionary ship drifted upon an uncharted ocean of
speculation without the compass of experiment to direct its course.
§2
Mendel’s work published in an obscure horticultural journal
remained neglected for forty years, till in 1900 his principle
was independently rediscovered by three continental workers--de
Vries, Tschermak, and Correns. During that period the study of the
reproductive process had progressed rapidly. The way was being paved
for new and spectacular developments of the atomistic standpoint
in heredity. To appreciate the subsequent elaboration of Mendel’s
hypothesis in its historical perspective a brief digression into the
anatomy of the cell is necessary.
Mendel’s researches were confined to plants. When he started his work
the nature of fertilization in animals was still obscure. The bodies of
animals like plants were known to be built up of microscopic bricks, or
_cells_ as Robert Hooke had called them. With the use of more powerful
microscopes this had gained general recognition during the thirties
and forties. Two centuries had elapsed, since Leeuwenhoek with the
first microscope had seen seminal fluid teeming with minute vibratile
bodies, the _spermatozoa_. At the end of the eighteenth century
that inquisitive ecclesiastic Spallanzani had shown that the sperm
is the essential constituent of the seminal fluid. By 1841 Kolliker
had traced the development of the spermatozoa from single cells of
the testis. It was not until 1875-9 that Hertwig and Fol working on
sea urchins independently observed for the first time in history the
penetration of the egg by the sperm, and established the universal
rule that fertilization involves the union of a single sperm with a
single egg cell. All modern discussion of genetic differences takes its
starting point from the fact that anything which is implied by the word
inheritance has its material basis in the microscopic sperm contributed
by the father or in the egg cell with which it unites.
In all animals the sperm is a microscopic entity. In all animals
from the jellyfish to Man with very few exceptions its appearance is
extraordinarily similar. It consists of a thicker portion to which is
attached a long vibratile process, or flagellum. The eggs of different
animals are of very different dimensions. Sometimes they contain
immense stores of food material (yolk). Sometimes as they pass to the
exterior by the female generative tract they are invested with an
additional slimy coat and a leathery or calcareous shell, secreted by
special glands. The immature egg of all animals is essentially similar.
In the living condition it is a spherical or ellipsoidal body in
which a clear spherical vesicle is seen; this vesicle present in all
cells is called the _nucleus_. The thicker part or body of the sperm
consists mainly of the nucleus of the cell from which it is derived. At
fertilization it swells up and unites with the nucleus of the egg. The
fertilized egg then divides into two separate segments or cells, and
the process of dividing is repeated an indefinite number of times. The
cells or segments into which the fertilized egg divides each contain a
nucleus, and the process of segmentation which involves the division of
cells into two is accompanied by the division of the nucleus of each
dividing cell. Like the testis or ovary the substance of all the organs
of the animal body is built up of the microscopic bricks which we
have called cells. In some tissues like bone and cartilage the bricks
are separated by a good deal of mortar. Others, such as the lining
membranes of the body, consist simply of cells packed tightly together.
At the beginning of embryonic existence all the cells are very much
alike. In the course of development the cells of different tissues
are considerably differentiated. Throughout all stages the process of
cell division always involves the partition of the nucleus in a highly
characteristic manner.
The details of this peculiar process, first elucidated by Flemming
and others during the seventies, has proved to be of astonishing
significance for the further understanding of Mendel’s hypothesis.
When a cell is about to divide, the nucleus looks like a tangle of
fine threads; and this tangle of fine threads resolves itself into a
number of readily distinguishable filaments which become progressively
shorter, assuming the appearance of stout rods staining deeply
with basic dyes. These rods, visible only with high powers of the
microscope, are the _chromosomes_, whose behaviour has provided us
with a tangible basis for Mendel’s conception of inheritance, and have
thereby permitted an extensive clarification and amplification of the
original hypothesis. From one point of view they might be said to have
done as much for the Mendelian conception of heredity as the discovery
of alpha particles has done for our belief in the atomic structure
of matter. As the dividing cell begins to constrict, the chromosomes
arrange themselves at its equator, and split longitudinally into
halves, each half travelling to opposite poles, where they spin out
again into fine threads from which the nuclei of the daughter cells are
built up. Thus each of the chromosomes in the nucleus of any cell in
the body is structurally equivalent to a corresponding chromosome in
the preceding or succeeding cell generation. About the year 1875 it was
recognized that this numerical constancy extends beyond the life of a
single individual. In every species of animal or plant the number of
chromosomes which can be counted in dividing nuclei is a constant for
the species.
With the discovery of this fact a new problem arose so soon as the
essential features of fertilization were appreciated. How is this
constancy maintained from generation to generation of new individuals?
Two investigators, Van Beneden and Boveri (1881-3), who worked on
the horse threadworm, a form which has only four chromosomes in the
dividing cells of the segmenting egg, showed that the egg and sperm
each contain only half the number of chromosomes characteristic of
the cells of the embryo. This conclusion turned out to be a perfectly
general one. Attention was immediately directed to the nuclear changes
which happen in the formation of the gametes. Innumerable cell
divisions occur in the testis or ovary of an animal. These are at first
similar in all respects to those which occur in the segmentation of the
developing embryo; but cell division goes on in the testis or ovary
throughout life. If we trace backwards the history of an individual
sperm or egg in the testis or ovary in which it originates, we find
a reduction of the number of chromosomes effected during the last
division but one, leading up to the formation of a sperm or ripe egg.
This penultimate division of the germ nuclei is preceded by the fusion
of the chromosomes lengthwise in pairs. When the division actually
takes place, each pair behaves like a single chromosome, splitting in
such a way that one member of each pair goes to form each daughter
nucleus. The succeeding division being normal, each gamete receives
half the number of chromosomes present in ordinary cell division. At
fertilization the normal number is restored. Thus each ordinary cell of
the body has a chromosome set of which half the components are paternal
and half maternal in origin.
In many animals and plants the chromosomes are very distinctly of
different sizes and shapes, and can be sorted out into corresponding
pairs. Such arrangements are constant for the species, and could only
be maintained constant, if each gamete contains one representative of
each pair. This means that the maternal and paternal constituents of
a pair are distributed in the reduction division to different cells.
The chromosomes therefore exist in pairs of which one element is of
maternal origin and one of paternal origin. Each gamete receives
one element of each pair, just as Mendel supposed that each gamete
contained either the paternal or maternal element of his paired
“factors.” By a curious coincidence this far-reaching conclusion was
first established in the very year which witnessed the application of
Mendel’s principles to animals by Bateson in England and Cuenot in
France (1902). Its recognition accompanied the elucidation of another
peculiarity of nuclear division, also destined to have important
theoretical consequences. In many animals there is found to be an
unequally mated pair of chromosomes, the XY pair. When this occurs, it
occurs in one sex only. In the alternate sex there is a corresponding
equal pair (XX). In birds and moths the female is the XY, the male
the XX individual. In other animals the male is usually found with
sufficiently careful measurement to have an unequal (XY) pair which
is equally mated in the female (XX). During the nineties it was found
that some animals had in one sex an odd number of chromosomes, a fact
which at first sight seemed to conflict with the numerical constancy
of the chromosomes. In the early years of the present century American
zoologists provided the key to an understanding of the discrepancy.
In all such cases the alternate sex has one more chromosome. The case
of the large cockroach will serve as an illustration. The male of
_Periplaneta americana_ (its technical name) has 33, the female 34
chromosomes. The eggs will all have 17 chromosomes. One-half of the
sperm will have 17, the other half 16 chromosomes. If a sperm of the
former class fertilizes an egg, the individual produced will be a
female (17 + 17 = 34); and if a sperm of the second type fertilizes
an egg, the individual produced will be a male (17 + 16 = 33). In an
animal with an unequally mated (XY) pair of chromosomes in the male
reduction will result in one-half of the sperm carrying the X and
one-half the Y chromosome. The eggs will all have the X, since this
chromosome is equally paired in the female. Thus an egg fertilized by
a Y-bearing sperm will become a male, while an egg fertilized by an
X-bearing sperm will develop into a female.
§3
By statistical reasoning Mendel had deduced from his experimental
data the existence of entities which behave just as the chromosomes
do. He had no direct evidence that his factors had any material basis
in the architecture of the germ cells. The new cell anatomy provided
independent confirmation of his predictions from an unexpected quarter;
but it was not immediately recognized that this was so. Antagonism to
the belief that the chromosomes fulfilled the requirements of Mendel’s
hypothesis is easily explicable. To Mendel’s first disciples his second
and first laws were equally sacrosanct. Mendel’s second law implies
that different pairs of hereditary factors behave quite independently
of one another. On such an assumption one of two deductions is
inevitable. Either the applicability of Mendel’s first law is extremely
restricted; or the number of factors is too large to permit of their
localization in the chromosomes. The sweet-pea, for instance, has only
seven pairs of chromosomes. If Mendel’s second law were as general as
the first, only seven pairs of factors could be accounted for by the
behaviour of the chromosomes. From this dilemma further development
of the atomistic view of heredity was rescued, when it was discovered
that Mendel’s second law is only a particular case of the possibilities
inherent in the first.
In 1910 Bateson and Punnet first discovered in the sweet-pea what they
then called “coupling and repulsion,” or as we now say, _linkage_.
Without going into the experimental data, we may define the phenomenon
of linkage in the following way. Suppose that these are two varieties
A and B which obey Mendel’s first law and two other varieties C and
D which likewise conform to its requirements, when crossed with one
another. Mendel’s second law stated that in a cross between AC and BD
the second generation will consist of the types AC, AD, BC and BD in
numerical proportions agreeable to the assumption that it is equally
likely that the factor determining A will be present in the same gamete
as the factor determining C or the factor determining D. Bateson
and Punnet found that this does not always happen. There is another
category of cases in which the factor which determines A sticks more
or less completely to the factor for C in preference to the factor for
D. The detailed analysis of these cases was at first made difficult
by Mendel’s literal symbolism, and his way of thinking of factors in
_pairs_. But the discovery of linkage at once led Lock to formulate the
fruitful suggestion that factors located on the same chromosome pair
would satisfy the requirements of linkage, while factors located on
different pairs of chromosomes would fit in with Mendel’s second law.
From this point onwards the most spectacular development came from
the study of inheritance in animals, and the significance of the
chromosomes was immensely reinforced by newly gained knowledge of sex
determination. Almost contemporaneously with the discovery of the sex
chromosomes or XY mechanism, as we now say, Leonard Doncaster had
elucidated in moths the phenomenon of sex-linked inheritance. This was
soon found to be of common occurrence in animals. Till this discovery,
which was made in 1905, the same results had always been obtained
in crosses of pure-bred varieties, whether the male or the female
parent displayed one or the other characteristic distinguishing them.
Doncaster’s work on the currant moth showed that there is a category of
cases which at first sight obey Mendel’s first law in its simplest form
when the cross is made in one way, but yield a different type of result
when the cross is carried out reciprocally with respect to the sex of
the parents. In such cases one sex is only able to transmit certain
characters to its offspring of the opposite sex. It was already known
that the XY sex (male in Man and most animals) can only transmit its X
chromosome to the XX type. The facts did not dovetail at first sight,
because sex-linked inheritance was originally elucidated in birds and
moths of which the female is the XY type. There was still an attitude
of hesitancy towards accepting Lock’s hypothesis, strengthened by the
persistence of an incorrect interpretation of the process of reduction
which had been made the basis of Weismann’s metaphysical speculations
concerning “germinal selection.”
When in 1914 Doncaster summed up the case for regarding the chromosomes
as the material basis of Mendel’s first law, a new era had already
dawned. Thomas Hunt Morgan, the central figure of a group of ardent
investigators at Columbia, had initiated a body of enquiries which
within half a decade eclipsed all other achievements that had
succeeded Mendel’s pioneer labours. About the time when Bateson first
encountered the phenomenon of linked inheritance Morgan began to rear
the fruit-fly Drosophila for breeding experiments. Till then genetic
experiment had been held in check by the slow rate at which most
convenient animals and plants reproduce and the expense entailed in
breeding them in sufficiently large numbers to permit statistical
inference. The fruit-fly completes its life cycle, if kept in warm
laboratory conditions, in a period of ten days. It is prolific. It
feeds on rotten banana skins. It therefore costs little to breed. To
these immense advantages it adds two others of supreme importance.
It has only four pairs of chromosomes readily distinguishable from
one another by size and shape; and it has produced in the laboratory
a crop of several hundreds of sports or _mutants_. Each mutant type
differs from the wild parent stock in some well-defined characteristic
inherited in crosses with the wild type in accordance with Mendel’s
first law. The mutant characters are extremely varied. One is
distinguished from the red-eyed parent by having white eyes, another
by having purple eyes, another by having no eyes at all. One is
distinguished by having wings that are practically vestiges, another
by wings that turn up at the tips, another by wings that are truncated
at their extremities. From the wild type which has a greyish body, one
mutant is distinguished by a deep black, another by yellow coloration.
The mutant characters are thus in general clear-cut differences
lending themselves to easy identification. With an animal that breeds
so rapidly and prolifically information accumulated with astonishing
rapidity. From data based on the study of a large assemblage of mutant
characters there soon emerged the precise requirements of Lock’s
hypothesis. All the mutant characters of Drosophila fall into four
groups. Members of the same group always tend to stick together in
hereditary transmission. Members of different groups like Mendel’s
dihybrids behave independently of one another. Of several hundred
mutant characters in Drosophila every one belongs to one of these four
linkage groups; and the number of chromosome pairs in Drosophila is
four.
This discovery was only the beginning of what might well be called
one of the faery tales of modern scientific research. In the way of
accepting Lock’s hypothesis there were still difficulties. It was in
evading the principal difficulty that Morgan’s school extended the
atomistic concept of heredity much further than his predecessors had
done. Till then the main outcome of experiments on breeding had been
to show that Mendel’s principle was of vastly wider applicability
than was at first supposed, and to engender the suspicion that the
patient unravelling of difficult and elusive cases would establish its
universal validity. As yet the world of Mendel’s atoms was without
form. Morgan and his colleagues gave it a map. Not content with
showing that Mendel’s atoms of heredity have their material basis in
the chromosomes, nor with actually identifying which chromosome is
significantly associated with a particular mutant character, Morgan
went further and localized the region of an individual chromosome in
which a particular Mendelian factor resides. He thus gave to Mendel’s
factors spatial co-ordinates in the living cell.
At the outset the study of linkage upon which the chromosome map is
based was facilitated in the case of Drosophila, because the varieties
dealt with were all known to be mutants from a fixed wild type. Thus
it was possible to break away from Mendel’s conception of “pairs”
of hybridizing characters. The Mendelian factor was replaced by the
mutant _gene_, by saying which is implied that a mutant arises because
at some point on a particular chromosome a physical change has taken
place. The gene is the Mendelian factor for the mutant condition, but
no assumptions are made about what determines the wild-type condition.
The inter-relationship of different characters is greatly simplified
by thinking only of the relation of one _mutant_ gene to another. The
discovery that all the genes fall into four groups corresponding to the
four groups of chromosomes presented one stumbling-block. Members of
the same group in general do not invariably stick together. When two
mutants are crossed the numerical proportions of the various types of
offspring give a definite value for the probability that the gene A and
the gene B will stick together or separate apart. This is a constant
for A and B. The constant used in practice is the tendency for A and B
to separate. Expressed as a percentage, it is called the _cross-over
value_. Some additional information was necessary to explain why A
and B do not always stick together, if they are associated with the
same chromosome. It was from the solution of this problem that the
chromosome map took shape.
Here the sex chromosomes came to the rescue. One very interesting
type of sport which has turned up in breeding the fruit-fly is not
recognizable by any discrete bodily peculiarity but merely by an
abnormality in the number of chromosomes. Of these the first to be
discovered was a type of female which has in addition to its usual
four pairs of chromosomes an additional Y chromosome. The XXY females
yield very extraordinary numerical results both as regards the sex
ratio and other characteristics, when used in making crosses involving
mutant characters. There is a class of mutant characters in Drosophila,
more than a hundred in all, distinguished by the fact that they are
not inherited symmetrically with regard to sex. They display linkage
_inter se_. They behave as “sex-linked” characters. The introduction of
XXY females into crosses involving such mutant characters results in
numerical ratios which are inexplicable on any assumption other than
the view that the sex-linked gene is referable to the X chromosome
alone. Yet, although the sex-linked genes are all borne on the same
chromosome, they do not invariably stick together in crossing. The
holistic chromosome clearly would not do. An atomistic chromosome had
to be put in its place.
The clue to this was provided by studying more closely the extent
to which the different genes stick together. Taking all the genes
located on the X chromosome this remarkable generalization emerged
from Morgan’s researches. If A, B, and C are three sex-linked genes;
if the probability that A and B will not stick together is _x_, and
the probability that B and C will not stick together is _y_, the
probability that A and C will not stick together is either the sum
or the difference of _x_ and _y_. The correspondence here stated is,
of course, subject to the margin of error permitted by the theory of
probability. To interpret this new _law of the linear alignment of the
genes_ Morgan made use of a structural peculiarity of the reduction
process. When the chromosomes pair in the reduction division, they
appear to become twisted. The appearance suggests that in the ensuing
split corresponding lengths of the original pair are interchanged. It
is very natural to assume that the likelihood that two points will be
separated from one another in such a manner is proportional to their
distance apart. So if the sex-linked genes are arranged in a series
along the length of the chromosome, the probability that A and C will
not stick together must be the sum of the probabilities that A and B
and B and C will be separated. This is just what experiment had shown
to be true. Thus all the genes on the X chromosome can be arranged in a
linear series. The intervals between consecutive genes in such a series
represents a space dimension.
The law of the linear alignment of the genes was soon found to apply
to the other groups of linked characters. Abnormalities in the
number of chromosomes have made it possible to identify each of the
remaining three linkage groups of the fruit-fly with its corresponding
pair of chromosomes. The first chromosome map of Drosophila was
constructed in 1916. It revealed the suggestive coincidence that the
number of ascertained points on each pair of chromosomes is roughly
proportional to its size. There is now very little doubt that the
work of the Columbia school has revealed an aspect of inheritance
which is of general significance. After years of patient work with the
relatively slow breeding sweet-pea, Punnet has at length elucidated
seven linkage groups corresponding to its seven pairs of chromosomes.
He has constructed a chromosome map of a seed plant on the basis of
the principle first established for the fruit-fly. A law which holds
good for two organisms so far apart in the evolutionary scale can
hardly be supposed to be lacking in universal validity. The chromosome
hypothesis may now take its place as one of the major generalizations
of biological science. The law of linear alignment has transformed
Mendel’s original conception of inheritance in a way which might
be compared with the elaboration of Dalton’s hypothesis after the
discovery of the law of combination of gases by volume. Mendel’s
atoms of heredity are now units spatially localized in larger units
of microscopically visible dimensions. These supermolecules are the
chromosomes.
Being a portion of living matter the chromosome is constantly
undergoing chemical change. Some critics of the chromosome hypothesis
have based objections upon this circumstance. The difficulty is more
apparent than real. Like the individuality of the modern atom the
individuality of the chromosome must be conceived in statistical terms.
For the discussion of the more familiar chemical reactions the statical
atom of traditional chemistry is adequate. For the interpretation of
hybridization experiments the diagrammatic chromosome of the text-book
suffices. In the field of radioactivity the statical atom makes way for
a dynamical model. So also in the domain of cell physiology we conceive
the chromosome as an ever-changing entity. The logical situation is
analogous in the two cases. Those who hold with Dr. Haldane that the
biologist must interpret his data in a manner different from that in
which the chemist or physicist interpret theirs have now to fall back
on the contention that the Mendelian view is only a partial picture of
heredity transmission. Anything which might have been said in favour
of this contention ten years ago has been weakened by recent work on
the inheritance of size. The pioneers of Mendelism selected clear-cut
hereditary differences which ordinarily manifest themselves in any
environment in which the animal or plant can live. They succeeded
in showing that a vast number of hereditary differences involving
a great variety of anatomical and physiological features conform to
the requirements of Mendel’s hypothesis. There was one category of
phenomena which remained obscure till quite recently. Differences in
size, height, body weight and the like vary greatly with environmental
conditions. Two stocks may be distinguished from one another by the
fact that the average member of one is measurably different from the
average member of another; but any given individual of one stock may
be indistinguishable from another individual of the other, because,
even when the environment is standardized as much as is practicable,
the range of variability of the two stocks overlaps. The analysis of
such cases cannot be undertaken by the ordinary technique of Mendelian
experiments; but certain statistical requirements of Mendel’s laws may
nevertheless be verified. By elementary statistical reasoning we can
deduce that the coefficient of variability of the progeny of a cross
between two inbred stocks must be a minimum in the first generation and
a maximum in the second. This has been shown to be true in a number of
crosses in which it is impossible to distinguish individual genetic
types by direct observation.
There is no longer any adequate reason to support the contention that
Mendel’s atomistic concept leads us to an incomplete understanding of
biparental inheritance in animals and plants. Those who assert that it
is so are now forced to fall back upon the last resort of obscurantism
by appealing to the magnitude of our ignorance. The modern theory of
the gene is a statistical construction consistently developed by a
logical interpretation similar to that adopted in elaborating the great
generalizations of physical science. The mechanist is often accused of
attributing vital processes to “chance” combinations of phenomena.
If the word chance is used to imply that we do not know the precise
conditions which determine such combinations, the statement is hardly
exceptionable. It might also imply that the phenomena which biologists
study can be successfully interpreted in terms of the mathematical
laws of chance. The history of Mendelism shows that these laws provide
a fruitful basis for predicting the behaviour of living systems, even
where physico-chemical hypotheses at present fail to throw light on
the phenomena which the biologist studies. The biologist is able to
progress to greater certainty of prediction only when he interprets his
data with the same logical method employed by the chemist and physicist
to deduce physical “laws.” Whatever the future holds in store for
further interpretation of heredity and variation on physico-chemical
lines, the progress already achieved has at every stage involved
elimination of holistic concepts by the ruthless application of
mechanistic logic. To the application of physico-chemical hypotheses no
branch of physiology has proved more recalcitrant than the physiology
of inheritance. No branch of physiology might more suitably be chosen
to cast doubt on Dr. Haldane’s recent statement that “anything which
can properly be called scientific physiology is impossible apart from
the assumption of _holism_.”
III. THE NATURE OF LIFE
“I am sorry then, I have pretended to be a philosopher: for I find
your questions very perplexing; and am in danger, if my answer be
too rigid and severe, of passing for a pedant and scholastic: if
it be too easy and free, of being taken for a preacher of vice and
immorality. However, to satisfy you, I shall deliver my opinion
upon the matter, and shall only desire you to esteem it of as
little consequence as I do myself. By that means you will neither
think it worthy of your ridicule nor your anger.”--David Hume, _The
Sceptic_
§1
Since a man must needs live before he can be a philosopher, no problem
of philosophy is more fundamental than the nature of life. There
is also no issue which provides more scope for vague, barren and
undisciplined discussion. A Regius Professor of Moral Philosophy,
whether he accepts the fact with resignation or refuses to do so, is a
piece of living matter. Perhaps this is why physicists are more vocal
than biologists in promoting a pacific solution of the territorial
dispute between science and traditional philosophy. At the present
moment it is the fashion among those who are writing on scientific
philosophy either to neglect the contribution of the biologist to
the world symposium, or to assume that the biologist in dealing
with living matter operates with different methods and different
concepts from those employed in physics. No phase in the history of
biology is more fitted than the present to illustrate the fundamental
unity of scientific method. In no branch of science is the limit of
applicability of scientific method a more significant issue.
Since a scientific concept is only a way of describing a class of
properties, the nature of life cannot refer to anything but the nature
of the properties of living things. Having arrived at some general
classification of the characteristic properties of living things, a
discussion of the nature of life in the light of modern biological
science presents two issues of pre-eminent interest. One is how far
the _methods_ employed in physical science have been successful
and are likely to continue to prove successful in dealing with the
properties of living matter. The other is how the increasing measure of
success which attends the utilization of purely physical _concepts_ to
interpret the properties of living matter is calculated to influence
our evaluation of the place of science in human thought. Whatever
differences of interpretation may exist among biologists on matters of
detail, it should at least be possible to infer from a survey of the
progress of biology whether the study of living matter is progressing
satisfactorily along the lines of quantitative analysis of experimental
data towards greater certainty of prediction, and whether there is good
reason to believe that the preservation of the teleological standpoint
in dealing with living matter is likely to ensure conspicuous success
in the same direction.
It may be admitted that there exists among biologists more unanimity
with reference to the first than towards the second issue. Every infant
science makes use of notions peculiar to its own province. Chemistry
has but lately passed beyond the stage when the concept of _affinity_
first became amenable to interpretation in thermodynamical quantities.
There are still many biologists who would assert that the concept of
_adaptation_ demarcates the province of biology from that of physics
and chemistry by an impassable gulf. There are others, fewer in
number, who, surveying the teleological growing pains of the more exact
sciences and bearing in mind that only 300 years have passed since the
properties of familiar chemical compounds were literally personified as
spirits of wood, spirits of salt and the like, do not feel compelled to
regard the concept of adaptation as final. They are able to entertain
the possibility that those properties which enable an organism to
maintain its continued existence as an organism are not permanently
more incapable of physical interpretation than the polarization of a
voltaic battery, a phenomenon which the consistent teleologist would
presumably regard as an attempt on the part of the latter to save its
own life. Clearly the onus of defining what precisely is implied in the
concept of adaptation lies on those who assert its uniqueness. Until
the vitalist is more definite on this issue, the mechanist is under no
obligation to refrain from classifying the properties of living matter
in the light of his own experience. The mechanist denies that anything
is to be gained by clinging to the teleological standpoint with its
implication of some extra- or intra-mundane purpose which has been
abandoned in all branches of science that lay claim to exactitude. He
refuses to deal with living matter except in as far as it is considered
as a series of “events” whose characteristics must be interpreted with
rigid economy of hypothesis.
In approaching any lump of living matter, let us say the author of
these essays, as an object of the external world, the maintenance of
economy of hypothesis compels the enquirer to seek as far as possible a
common basis for the characteristic properties of living and non-living
systems. This necessitates a clear definition of the distinction
between the two. Taking a comparatively complex organism, as, for
instance, the common frog, a distinction might be attempted along the
following lines. In the first place, its possibilities of behaviour
are more varied than those of any machine which can be manufactured
by man; yet, while possessing a greater range of reversible response
than any non-living system, it would be difficult to specify in a
living system any single activity which could not be reproduced by a
mechanical system. Apart from this diversity, which we may refer to
under the generic term _reactivity_, living matter is characterized
in general by the wide range of external influences which are
significant in determining its characteristic reversible responses.
This peculiarity, in view of the subjective preconceptions implicit
in the older terms irritability, sensation, etc., may be denoted by
the term _receptivity_. Here again it is impossible to isolate any
single agency (or “_stimulus_”) capable of evoking reversible change
in any living system and incapable of evoking reversible change in
any non-living system. Finally--and at first sight--a more diagnostic
difference between living and non-living matter is seen in the property
of _reproduction_ (taken in the broader sense of the term, to include
growth). A given piece of living matter comes into being in our
experience only through the agency of other pieces of living matter
closely resembling itself.
§2
Were the more obscure process of sexual reproduction universally
characteristic of living matter, this distinction would appear
especially fundamental. Experimental biology is far from the
achievement of a complete physico-chemical analysis of asexual
reproduction in any type of organism. On the other hand, in the life
cycles of those multitudes of micro-organisms which multiply by simple
fission after attaining a certain limit of growth, there is nothing
which compels an unprejudiced investigator to regard the process as
more intrinsically incapable of physical interpretation than the
splitting into two of a liquid drop. Although our knowledge of the
nature of sexual reproduction is fragmentary, in this very field some
particularly spectacular advances have been registered in substituting
physical agencies as effective instruments for initiating processes
which at one time were only amenable to the influences of living matter
itself. Thirty years have now passed since Loeb’s discovery that
changes in the osmotic pressure of the external medium or alteration
of the permeability of the egg itself, leading to changes in its own
internal osmotic pressure, can initiate without any assistance from the
sperm the development of the ovum into a new and complete organism.
That discovery was the starting-point of a body of investigations whose
influence has radiated into many other fields of biological enquiry.
Especially noteworthy in this connexion is the work of Warburg during
the last decade. Warburg was able to show that sea-urchin eggs, and
later animal cells in general, if rapidly dehydrated and ground to
a powder, will, like the intact cell, absorb oxygen for some time
when moistened. He showed also that this property, like respiration
in the intact cell, can be abolished by the action of cyanides and
other classes of tissue poisons. By doing so, Warburg has taken a
characteristic and highly complex property of living matter out of
the realm of vitalism into that of physical chemistry. His analysis
went further. Experiment showed that three classes of poisons which
inhibit tissue respiration can be distinguished by their quantitative
relations. Of these, the efficacy of one class, the cyanides, was
shown by Warburg to be correlated with the iron content of the
cell. On the hypothesis that iron catalysis is the main factor in
the oxidation of organic material in the cell, Warburg manufactured
suspensions of charcoal with a high iron content capable of catalysing
the auto-oxidation of sugars, fats, etc. The catalytic activity of
these suspensions was found to be related quantitatively to the three
categories of respiratory poisons in a manner closely parallel to the
action of the latter on tissue respiration.
Though reproduction is, in some respects, to the biologist at least,
the most fundamental of all the three features which I have defined
above, the ever-changing reactivity and manifold receptivity to
external influences so characteristic of living matter pre-eminently
engage our attention in connexion with the more intimate and subtle
issues of a field of enquiry which biology may yet claim. I refer to
the analysis of human behaviour. In this connexion I shall mention
progress in three directions as illustrating the transition from
teleological to quantitative treatment during the last half century;
namely, the physical analysis of the events which constitute an
isolated unit of response or reflex, the integration of reflexes in the
normal behaviour of animals, and the determination of new behaviour
patterns along the lines laid down by Pavlov’s school. With regard to
the first, we will consider the effect of flashing a bright light upon
an animal that has been previously kept in the dark. The characteristic
response, let us say, blinking of the eyelids, and the intervening
events involved are, first, a physical change in a receptive area,
namely, the retina; secondly, the propagation of the disturbance
there set up along a certain path, the nervous system; thirdly, the
liberation of a considerable quantity of energy at the seat of response
or effector organ, that is to say, the muscles of the eyelid.
Our knowledge of the nature of receptivity is least complete. That it
is a measurable physical event is beyond dispute. When light impinges
upon a given area of the retina there follows a characteristic series
of changes in electrical potential of the excited area with reference
to a non-excited area. Through the work of Jolly, Adrian and others
the sequence, the time relations and the magnitude of these changes
are being related to the intensity and duration of the stimulus
within predictable limits for a given species. These events initiate
the propagation of the disturbance known as the nervous impulse. The
nervous impulse is a physical event whose space-time relations can be
defined as concretely as the passage of an electric current through a
wire. Three-quarters of a century ago Helmholtz showed that the time
which elapses between the application of a stimulus to a nerve and
contraction of its attached muscle is a linear function of the distance
between the latter and the point of application of the stimulus. The
conception of the nervous impulse as a physical event had been, till
this discovery, entirely repugnant to scientific thought. We now know
not only, as Helmholtz showed, that the nervous impulse has definite
space-time co-ordinates, but that it has the dimensions of energy. Its
passage corresponds to the rate of propagation of an electrical change
of an analogous character to the electrical response of the excited
retina. The total energy of its propagation has been recently measured
by Gerrard and A. V. Hill from determinations of heat production during
its passage. Its mass relations are attested by a measurable increase
in the carbon dioxide production of stimulated nerve. The rate of
propagation of the nervous impulse varies like all chemical reactions
in a characteristic way with increase in temperature. The goal of the
nervous impulse after it has traversed one or more synapses in the
central nervous system is the effecter organ itself--in the case of
blinking of the eyelids, a muscle fibre. During the past two decades
a series of brilliant researches based on calorimetric methods have
revolutionized our knowledge of the final component of the reflex.
A. V. Hill and Meyerhof have correlated the chemical and energetic
changes accompanying muscular contraction with a precision of the order
expected in purely physico-chemical determinations. They have shown
that the total energy of muscular contraction can be quantitatively
related to the energy liberated _in vitro_ by the breakdown into lactic
acid of an amount of glycogen equivalent to that which is converted
into lactic acid in the actual contractile process.
Passing from the analysis of the constituent events of the reflex to
the integration of reflexes in normal behaviour, we are faced with a
striking change in the attitude of enquiry adopted in the study of
those aspects of behaviour determined by generalized stimuli such as
light and gravity and denoted by the term _tropisms_. Three-quarters
of a century ago, after Helmholtz had dispelled the belief that
identified the nervous impulse with an imponderable psychical
principle, biologists like Lubbock were content for the most part with
the statement that the moth flies towards the candle because it likes
the light. The work of Loeb and others has shown that the state of
contraction of particular groups of muscles is reflexly determined by
the stimulation of particular areas of the retina. It is a mechanical
necessity that when different areas are unequally stimulated,
differences in tension of different groups of muscles will bring the
body into such a position that symmetrically opposite areas will be
equally illuminated. The animal must move, as in fact it does, along
the path of the incident beam, whether by so doing it brings itself
into a brighter, or, as can easily be arranged experimentally, a darker
situation. Whereas the older and purely teleological attitude permits
us to predict nothing of consequence, the objective interpretation of
tropisms by experimental methods permits us to make many verifiable
predictions, as, for instance, the fact that the moth will move in
circles, if one eye is blackened, owing to the fact that the muscles on
that side will be more relaxed.
By the end of the nineteenth century, experimental biologists were
generally disposed to the belief that the analysis of the reflex and
the integration of reflex systems were problems not of apologetics but
of energetics. Investigation had been confined to those aspects of
behaviour which are for practical purposes invariable responses to a
particular situation. From the human standpoint the most fascinating
feature of the behaviour of an organism is, after all, the extent
to which its behaviour is conditioned not by the immediate but by
the antecedent situation. In the opening years of this century the
researches of Sherrington were elucidating the integration of reflexes
in normal behaviour. Restricted as they were to the decerebrate
animal, the traditional distinction between reflex and voluntary
activity remained as a defeatist formula in biological nomenclature.
The distinction was not a gratuitous olive branch to introspective
philosophy. It had its objective basis in the domain of behaviour
which is not uniquely determined by the immediate stimulus, when all
synchronous conditions have been standardized. That distinction has
been superseded to-day by the work of Pavlov’s school, which has shown,
first, that in the higher animals with the cerebrum intact, new reflex
systems can be built up experimentally under perfectly definable and
reproducible conditions; that the relations between such conditioned
reflexes can be defined in the language of space and time; and that the
concept of sensation can be externalized by reference to the ability of
a given stimulus to become a specific agent in the building up of a new
reflex system. In short, it is legitimate to anticipate the possibility
of giving a complete specification of how such an animal as a dog
will behave in a given situation without recourse to the traditional
nomenclature of memory, consciousness, sensation, etc.
Pavlov’s work is now accessible to the English reader through two
translations of the Russian physiologist’s own writings and several
excellent résumés, such as the one given in Lovatt Evans’ _Recent
Advances in Physiology_. How far-reaching are its consequences has not
been widely recognized even by biologists themselves. Experimental
biology, during its brief career, has attempted to accommodate itself
to the introspective temper of traditional philosophy by a compromise
explicitly formulated in the writings of Descartes, who bequeathed
to physiology the dualism of mind and matter. In conformity with the
Chaldæan mythos, many philosophers, Descartes among them, have endowed
Man alone with soulfulness. The coming of the Evolutionary hypothesis
has broken down so inflexible a distinction between Man and other
forms of living matter. Evolutionists in the nineteenth century, like
Haeckel, were prepared to equip the Amœba with a soul. In our time
the Cartesian compromise has again shifted its boundaries. By the
beginning of this century the moth once more had gone to join the
candle. Still Man stood with a little family of mammals around him,
each with one leg on either side of the frontier that separates the
universe of space and time from the Platonic world of universals.
Pavlov has taken those aspects of behaviour which would have been
referred twenty years ago to exclusively introspective concepts, and
has treated them successfully as predictable configurations in a
space-time framework. The little family of mammals has been let through
the tollgate of the Cartesian compromise. A new school of psychologists
has come into being with the express object of making psychology a
physical science, relieving Man, the celestial pilgrim, of his burden
of soul.
Philosophers have always had a legitimate cause for complaint that
biologists were unable to deal with those aspects of human life
which interest people most. The distinction between reflex and
voluntary activity provided the fullest absolution for that amiable
libertarianism which we all entertain under the influence of alcohol
and love. Because that distinction was implicit in the outlook of the
most radical mechanists of the last generation, Loeb among them, Dr.
Haldane finds it so easy to point out the inadequacy of the mechanistic
outlook. In the light of Pavlov’s work we can now envisage the
possibility that the methods of physical science will one day claim the
whole field of what can be properly called knowledge. If I am right in
cherishing such an opinion, it would thus appear that the investigation
of the conditioned reflex initiates a new epoch in biology, pregnant
with more far-reaching philosophical implications than the evolutionary
speculations of the nineteenth century. The fact that no reference to
the conditioned reflex is contained in Dr. Haldane’s Gifford Lectures
may in part account for the fact that he can so easily dispose of the
mechanistic position. The modern mechanist does not say that thought
and love and heroism do not exist. He says, show me behaviour to
which you apply the adjectives thoughtful or loving or heroic, and we
will, one fine day, endeavour to arrive at predictable conclusions
with reference to it by following the only method of enquiry which
we have learned by experience to trust. When Dr. Haldane goes out of
his way to dispose of the puerile formula that thought is a secretion
of the brain, as bile is a secretion of the liver, and does so, I
gather, under the impression that mechanists either believe it to mean
something or alternatively shut their eyes to the major problems of
existence, I can only respectfully suggest that he is flogging a dead
horse, while the living ones are getting out of the vitalistic stables.
I have endeavoured so far to indicate the increasing measure of
success that has crowned the application of physical methods and the
use of physical concepts in modern biological investigation. I have
attempted to illustrate the continuous retreat from teleological
concepts that has accompanied this advance. In asking what progress
may be anticipated from encouraging the teleological attitude to the
nature of life, I wish now to urge that the important advances of
biological science during the last hundred years have not only involved
continual abandonment of teleological concepts, but have consistently
been made in the teeth of opposition from the vitalists, organicists
and holists of their time. A century ago, in the same year that
witnessed Wöhler’s announcement of the successful synthesis of Urea,
the great chemist Henry wrote (1827) concerning organic compounds:
“It is not probable that we shall ever attain the power of imitating
Nature in these operations. For in the functions of a living plant a
directing principle appears to be concerned peculiar to animated bodies
and superior to and differing from the cause which has been termed
chemical affinity.” Only six years before Helmholtz’s determination
of the velocity of the nervous impulse in 1851, Johannes Müller had
declared that to measure the propagation of that imponderable psychical
principle was a theoretical absurdity.
It is not unlikely that before another celebration of the centenary
of Wöhler’s achievement, Fischer’s synthesis of an octadecapeptide
will have been surpassed by the manufacture of complex proteins in the
laboratory. Looking forward a little in the light of what success has
crowned the construction of physical models of vital processes, it
is, as Sir Edward Sharpey Schafer scandalously suggested at a meeting
of the British Association some years ago, perfectly legitimate to
entertain the possibility, even the likelihood, that scientists will
one day construct from artificially synthesized organic materials,
systems with so wide a range of reversible reactivity and receptivity
to external influences that they would be called organisms, if met with
in Nature. While taking a more hopeful view in this matter than some
biologists, I would remark that the validity of the mechanistic outlook
is quite independent of this possibility. The security of any dynamical
system of treating the motions of the heavenly bodies is independent of
the possibility that human effort could manufacture a new satellite for
Jupiter.
§3
If we can assert that the present phase of biological enquiry is
a peculiarly fruitful one, and that there is no reason to see any
immediate cessation of progress in the use of physical concepts as
the basis of our analysis of the properties of living matter, can we
not go further and state that we have absolutely no encouragement
for entertaining the hope that any deeper knowledge will accrue from
apostrophizing under the sobriquets of entelechy, life force, élan
vital that elusive entity to which, perhaps, the poet William Blake
referred as Old Nobodaddy? It is doubtful whether we shall see a
recrudescence of such frankly animistic devices as these. As biology
becomes more technical and more exact, an aptitude for rehabilitating
oriental mysticism in somewhat unusual verbiage will be regarded
as an insufficient equipment for entering the field of biological
controversy. The investigator who abandons physics for the pursuit
of biology will contribute new ideas. Fruitful contributions need no
longer be expected from those who combine the pursuit of literature
with an amiable interest in natural history. The days of Butler and
Bergson are passed.
Dr. Haldane, the most vigorous contemporary critic of the mechanistic
standpoint, is very anxious to avoid any suspicion of being tainted
with the cruder forms of vitalism. He disowns any allegiance to the
life force, élan vital et hoc genus omne, except in so far as he,
somewhat mysteriously, contrives to introduce an adventitious deity
into the latter portion of his Gifford Lectures. This does not make
its appearance until his major thesis is complete. Anxious as is Dr.
Haldane to disclaim adherence to the tenets of vitalism, he is very
definite in denying the possibility that atomistic concepts will
ever successfully deal with the problem of what he calls “conscious
behaviour.” In the light of Pavlov’s work we see that the problem of
what is usually called conscious behaviour, or as we should rather say
_conditioned behaviour_, can now be approached as a problem in the
study of those conditions which determine whether a new reflex will,
or will not, be brought into being. We may state this in other words
by enquiring how the passage of impulses along particular tracts in
the central nervous system _influences the facility with which the
nervous impulse will pass across a particular type of synapse_. Since
the problem of the conductivity of the synapse is, as we have seen,
an essentially physical problem, it is not overstating the case to
say that the work of Pavlov’s school has brought the study of what
Dr. Haldane calls “conscious behaviour” within the realm of physical
enquiry. Once this is fully grasped it no longer seems incredible
that the interpretation of conditioned behaviour will eventually come
within the scope of physico-chemical analysis. Contrary to the holistic
standpoint, we are thus led to an atomistic concept of individuality.
This I shall venture to formulate as _the statistical probability
that in an immensely elaborate system of reversible reactions a
certain number of states characteristic of any given moment will be
reproducible at another moment_.
In his Lowell lectures Professor A. V. Hill lays down two general
conclusions derived from the extension of modern biological enquiry.
First, as I have endeavoured to show, there is no limit to the extent
to which the mechanisms of life can be elucidated with the aid of
physical methods and concepts. Second, that, however far we get, we
shall still find function, adaptation, organization and purpose in
the processes we explore. I would venture to suggest that, however
alluring such a compromise between vitalism and mechanism may appear,
these two conclusions, though formally in nowise inconsistent, are,
nevertheless, in practice incompatible. As Henderson points out in his
_Fitness of the Environment_, if we wish to indulge in teleological
phantasies, we can find as much scope in physics and chemistry as in
biology. We do not dismiss the hypothesis that thunderstorms occur when
a blue unicorn sneezes on Uranus, because it is actually possible to
disprove so engaging a fancy, but simply because other ways of treating
thunderstorms lead to more useful conclusions.
Hence it seems to me that as we come to understand more and more about
the mechanics of living systems by using methods of which Professor
Hill is so brilliant an exponent, we shall inevitably find ourselves
talking less and less about purpose and function. In consequence many
of the problems which now engage the attention of philosophers will be
relegated to the same status as the philosopher’s stone. No doubt such
a change will come very gradually, so gradually that we shall hardly
notice it. Nevertheless, one may venture to predict that philosophers,
already forced by the developments of modern physics to divert their
attention from the pretentious crossword puzzles of the Hegelian
tradition, will sooner or later be driven to take account of the
post-evolutionary developments in biology, and more especially those
which have their starting-point in Pavlov’s researches.
By undertaking the analysis of the characteristics of conscious
behaviour without departing from the methods of the traditional
physiology of reflex action, biological science in our generation has
shown that there is no nicely defined boundary at which physiology
ends and moral philosophy begins. Hitherto physiology and academic
philosophy have developed independently, because physiologists
themselves have accepted the common sense dualism of mind and matter.
Moral philosophy can no longer claim that there is any distinctive
aspect of the Nature of Life, which lies beyond the province of
physiological enquiry. If any fundamental distinction between mind
and matter remains, that distinction henceforth defines the antinomy
of a _public world_ of common beliefs which all can share, the
conceptual world of science in which ethical neutrality and economy
of hypothesis reign supreme, and, in contradistinction to that public
world, many _private_ worlds which for the present remain impenetrable
through the medium of discourse. Biological science is continually
socializing our beliefs. What seems irrevocably part of the private
worlds of one generation becomes irrevocably part of the public world
of its grandchildren. Thus the new pluralism will not be, like the
Cartesian system, static, but dynamic. It is ever tending towards a
monistic outlook as a limiting case. Such a monism, unlike traditional
materialism and traditional idealism will be regarded not as a formula
but as an asymptote. It is evidently immaterial to _public_ discourse
whether we _privately_ entertain the view that _the_ public world is
more or less _real_ than _our_ private worlds. It would thus seem that
as biological science invades the province of human behaviour the
concept of _publicity_, as I venture to call the communicability of
beliefs, will come to occupy the status of importance which _reality_
has held in the systems of egocentric philosophers.
The public world, as I have conceived it, is a construction based on
the continuous extension of the principle of mechanism. The principle
of mechanism, that a complex system is interpretable only by reference
to the properties of its constituent parts, is not urged in the spirit
of dogmatic assertion, but because it has served us well in the past.
We still await any single verifiable conclusion that is uniquely
developed from any alternative principle. Holism, the newest form
of Vitalism, claims to have found an alternative or supplementary
principle that is essentially teleological. The holist does not specify
by reference to any single concrete situation how he proposes to use
his principle. It is admitted even by the mechanist that we are not
in a position to construct a symbolic relation which will completely
describe the vagaries of a Ford car in terms of the field equations
of the proton and electron. Does the holist wish us to believe that
we can help anyone to drive a car by assuring him that at every level
of complexity between the internal structure of the atom and the
newly licensed automobile there emerges an ever-increasing urge to a
wholeness or unity which is somehow indefinably different from the
interaction of the parts? Verily the mechanist of all people knows that
we know in part and we prophesy in part. For this very reason, because
he is prepared to await with patience the slow advance of science, he
refuses to subscribe to high-sounding pseudonyms for ignorance and
principles that are never seriously intended to be put into practice.
In the recent symposium on _The Nature of Life_ before the British
Association both General Smuts in his exposition of the holistic
standpoint and Dr. Haldane who supported him dwelt upon the supposed
collapse of mechanistic principles in physics itself. The former
cited in support of his point a somewhat rhetorical remark by Dr.
Whitehead in this sense. It is of course evident that if our mechanical
principles undergo modification our biological interpretations must
share in the general change of outlook. It is, therefore, beside the
point to criticize the mechanistic standpoint on the ground that our
mechanical principles are undergoing revision. Let us examine this
objection a little more closely. Experimental biology, we are told,
has been directed towards the attempt to describe the properties
of living matter in terms of the traditional physical concepts of
mass, length, time, energy, etc. Since these concepts now appear to
be less fundamental than we once believed, the hope that a complete
mathematical description of the universe is realizable, has, as
Mr. Sullivan asserts with triumphant _naïveté_, “no longer any
plausibility.” Surely it is evident that a signal advance towards
a more monistic interpretation of nature has been made, when the
analysis of any biological phenomenon has been achieved with the aid
of traditional physical concepts, and when concepts once peculiar
to biology, as affinity was once peculiar to chemistry, have been
translated into the traditional language of physics. Physics to-day
is seeking a new synthesis to take into one system of equations all
the old data, and many new ones which have lately accumulated. This
is not a new situation. The old mechanics remains as valid as ever
for the realm in which it was developed to operate. To effect a more
comprehensive scheme it has been necessary to examine many of the
old postulates. In the meantime we have to recognize that we are not
so near to a single unifying hypothesis as the rise of energetics
led the physicists of Kelvin’s generation to hope. What does this
signify? Certainly not that mechanics has abandoned the principles
of mechanism. Is it not rather a fact that the modern physicist is
complaining that the inadequacy of Newtonian principles is in part
attributable to teleological implications insufficiently recognized
till now? The very hope of finality which Kelvin’s generation
entertained seems from the new mechanistic standpoint, as I have stated
it, to savour of scholasticism.
In taking this line General Smuts and Dr. Haldane seem to me to have
laid bare the source of a misunderstanding that lies at the root of
most of the criticism which vitalists old or new direct against the
new or the old mechanistic standpoint. Those who have the scholastic
predilection for finality and the scholastic predilection for the
abstract noun, do not seem to be able to believe in the existence of
people who are not like themselves. They cannot, it appears, understand
that unless one starts off with the obsession that the universe can
be summed up in a monosyllable, one is under no imperative necessity
on the one hand to be resentful towards or disappointed with science
because it lays no claim to the finality of religious dogma, nor
on the other to make the assumption that such finality ought to be
obtainable. The mechanist does not claim that his system is, or ever
will be, complete in the sense that science will one day find an answer
for all the conundrums which the scholastic temperament dictates. On
the contrary, it is the essence of the mechanistic position that there
is a technique of asking questions profitably as well as a way of
answering them satisfactorily. All the mechanist claims is that as far
as we can see at present his way of dealing with things leads to the
most complete unanimity which it is possible to attain. Against the
old vitalism, that of Dr. Haldane, who denies that the principle of
mechanism can ever deal with conscious behaviour the older mechanistic
outlook was secure in the assurance that, if the principle of
mechanism failed at such a level, no other principle led to verifiable
predictions in the same field. Against the new vitalism or holistic
standpoint of General Smuts which no longer asserts dogmatically that
the principle of mechanism is inapplicable at any specific level of
existence, but contends that it does not anywhere give a complete
account, the new mechanistic or _publicist_ standpoint which I have
outlined contends that if the principle of mechanism fails to give a
complete account at any level no alternative or supplementary principle
has been discovered. The reply of the mechanist old or new to the
vitalist old or new is that of Mr. W. B. Yeats’ faeries:
“Is anything better, anything better
Tell us it then...”
It follows that, in any discussion between the two, the combatants
are generally at cross-purposes. The mechanist is primarily concerned
with an epistemological issue. His critic has always an ontological
axe to grind. The mechanist is concerned with how to proceed to a
construction which will represent as much about the universe as human
beings with their limited range of receptor organs can agree to accept.
The vitalist or holist has an incorrigible urge to get behind the
limitations of our receptor organs and discover what the universe is
_really_ like. What we mean by _really_ in this connexion evidently
depends upon whether we view the question socially or individually. In
our relation to other human beings the nearest approach to what the
universe is really like is found in the schematization of our common
experiences. If there is any other reality its sanction is non-social.
Thus in contradistinction to the _reality_ of traditional philosophy
which is an individualistic concept, the concept of _publicity_, which
it is proposed to substitute as the goal of synthetic philosophy, is an
essentially social one.
IV. THE CONCEPT OF ADAPTATION
“No philosopher who is rational and modest has ever pretended to
assign the ultimate cause of any natural operation, or to show
distinctly the action of that power which produces single effect
in the universe. It is confessed that the utmost effort of human
reason is to reduce the principles productive of natural phenomena
to a greater simplicity.... The most perfect philosophy of the
natural kind only staves off our ignorance a little longer, as
perhaps the most perfect philosophy of the moral or metaphysical
kind serves only to discover larger portions of it.”--David Hume,
_Sceptical Doubts_
§1
By those who hesitate to commit themselves to an explicit advocacy of
either the vitalistic or mechanistic views about the Nature of Life it
has often been urged that the concept of adaptation is fundamental to
biological science. Professor A. V. Hill is perhaps the most brilliant
physiologist now living. He adopts a hopeful attitude to the progress
which awaits further analysis of the properties of living matter in
physico-chemical terms. He also thinks that, however far mechanistic
principles are extended, the biologist will always encounter
“adaptation” in the phenomena which he studies. Another distinguished
physiologist, Professor Lovatt Evans has expressed himself in rather
more emphatic terms.
“Physiologists,” he states, “in attempting to know what life is,
have in my opinion attempted too much, and I think that a new point
of view is essential.... The idea of adaptation, urged by Claude
Bernard, should be adopted by physiology as its basal principle, as
the chemist accepts the conservation of matter or the physicist
the conservation of energy. We need not seek to know why it is so,
that is the province of the philosopher.... It is not a definition
of what life is, but a brief statement of its way.... Life is
conserved by adaptation.”
When I first read these words I was not sure that I agreed with them.
I was not quite certain that I knew what they meant. I had already
come to the conclusion that the word adaptation is frequently used
by biologists without a very clear agreement as to its content. I
cannot subscribe to the view that there is a sort of trade union of
philosophers to which physiologists are ineligible, unless they can
show their articles of apprenticeship. Nor can I conceive what is meant
by a concept of life except such as is implied in a statement of _its
way_. A scientific concept defines a class of properties. A scientific
concept of life or adaptation must conform to this requirement. In
this essay my object is not to criticize Professor Lovatt Evans for
whose breadth of view I entertain a very sincere respect. I have
quoted his words, because they focus attention on some significant and
controversial issues. They serve to reveal how imperative it has become
that biologists should agree about the sense in which they intend to
use the word _adaptation_.
The quotation given above might be interpreted to mean two very
different things. If the term adaptation is used to define certain
very general characteristics of living systems, it becomes almost
co-extensive with a scientific concept of life itself. If we use
_principle_ in a somewhat archaic sense to indicate a field for
investigation, like the principle of affinity or the active principle
of the thyroid gland, there can be no question that the idea of
adaptation is the basic principle of physiology. The comparison of the
biologist with the chemist or physicist seems to go beyond this, and
imply that adaptation is not something to be explored and interpreted,
but part of the logical procedure of biology, something by the aid of
which we can predict conclusions of universal validity in the field
of biological enquiry. I do not think that Professor Lovatt Evans
really means this. I do urge that biologists continually confuse within
the compass of the concept of adaptation the notion of a problem for
solution and of a _vera causa_. This in everything but verbiage is
precisely what the cruder type of vitalist does, when he invokes the
vital principle. He first introduces a term to describe a large number
of things about which we are ignorant and wish that we knew more. He
then falls into the trap of imagining that the invention of a new term
has solved the problem.
Quite apart from this difference which, if it is to define the scope
of our scientific enquiries, cannot be dismissed as metaphysics,
biologists differ a good deal concerning the extent of the phenomena
and the kinds of phenomena they are dealing with, when they speak
of adaptation. The physiologist--in the restricted sense of the
term--is usually referring to something which might be called
the self-regulating characteristic of the body. The evolutionary
biologist--who to-day is a physiologist in the broader sense of the
term--is usually thinking of “a change in the structure, and by
implication also in the habits of an animal which render it better
fitted” for life. I here quote Professor D. M. S. Watson’s suggestive
address on adaptation from the evolutionary standpoint.[3] Sometimes
the word adaptation has a more comprehensive significance and includes
both definitions which I have distinguished. It then amounts to saying
that living systems are self-regulating and self-propagating, which
is one way of defining the nature of life as a scientific concept.
None of these technical uses of the word adaptation imply anything
that the most dogmatic mechanist could decry. If we define adaptation
as the self-regulating processes by which living matter retains its
recognizable characteristics, it is a truism to say that life is
preserved by adaptation. In that case, if adaptation is to be made
the paramount issue for biological enquiry, we can hardly upbraid our
predecessors for presumptuously seeking to know what life is. If we are
to reach any agreement about the use of the word adaptation we must
therefore retrace our steps, and examine more closely what are the
characteristics of a living system. It is useless to define the goal
of biological enquiry in terms of a concept which is as vague as life
itself. I suggest that when, in its various uses, the term adaptation
has any objective utility, it refers to these two more or less
distinct categories of characteristics which living beings display,
i.e. self-regulating and self-propagating. They are separable issues
inasmuch as a worker bee and a Dominican friar are self-regulating but
not self-propagating systems. There is no particular reason to object
to the use of the prefix, so long as no personalistic implications of
the word self are imposed upon it without further discussion.
§2
Of the two ways in which the word adaptation is used in biological
discussion, that which implies the notion of self-regulation is
most fundamental. A living organism is an extremely complex system
in dynamic equilibrium with its environment. The idea of dynamical
equilibrium is not peculiar to biology. The atom, which for traditional
chemistry was a statical concept, is no longer regarded in that way
by the modern physicist. What is more peculiar about living matter
is its amazing complexity, and the idea of adaptation in the sense
of self-regulation calls attention to the fact that a system of such
extreme complexity, a system with so many characteristics, continues
to maintain its individuality, i.e., its manifold characteristics,
in spite of all the changes that are taking place within it and
without. The recognition of this complexity is common ground. If the
mechanist underrates the difficulty of the problem, he is certainly
to be discouraged, except in so far as the scientist in attacking any
problem must always focus his attention on a limited range of data
and rule out certain things as insignificant for his present purpose.
It may be true, as Professor Lovatt Evans opines, that mechanistic
interpretations tend to become arrogant and superficial. Is he on surer
ground in holding that “it is unthinkable that a chance encounter
of physico-chemical phenomena can be the explanation”? Might we not
reflect with David Hume that “our own mind being narrow and contracted,
we cannot extend our conception to the variety and extent of nature,
but imagine that she is as much bounded in her operations, as we are in
our speculation”?
Scientific hypotheses are not always thinkable, if by that we mean
pleasant, easy or conformable to common sense. Our grandfathers
thought it “inconceivable” that her Gracious Majesty, Queen of Great
Britain and Ireland, Empress of India and Defender of the Faith,
could be descended from an ape. The atomic structure of matter was
unthinkable to many people little more than a century ago. To-day the
quantum atomic model is unthinkable; but we think it is the best way
of interpreting the data. Given this amazingly complex system in
dynamically stable equilibrium with its environment, we have to decide
consistently with the fullest requirements of the problems what is the
most economical way in which we can envisage its existence. Seeing that
a mechanistic interpretation is evidently the most economical one, the
real issue is to decide whether there are any characteristics of the
complex which are inconsistent with such an attitude.
From the modern standpoint the individuality of the atom is a
statistical concept. The atom is in dynamically stable equilibrium
with its surroundings. It might, therefore, be argued that a Ford car
is an example of a complex mechanism which is in dynamical equilibrium
with its environment. This would be a superficial analogy for the
order of complexity which we encounter in living matter. The molecular
constitution of the parts of a Ford car is comparatively static. In
the minutest parts of an organism new molecules are being built up and
replacing others that have been broken down. Nevertheless, in all this
astonishing panorama of microscopic revolutions which underlie the
microscopic continuity of the organism we know of no events which are
in conflict with the great generalizations of physical science.
On this point Professor Hill speaks with special authority, when he
declares:
“Fortunately for physiology several of the generalizations of
science appear to be fairly strictly true, even when applied
to the living organism. Although such exact experiments are
not possible on man, or animals, or plants, as may be made on
non-living objects, there is little evidence--indeed, I would be
bold and say there is no evidence--that such living creatures can,
in any manner or degree, evade the ordinary laws of mechanics,
chemistry and physics, the principles of the Conservation of Energy
and Mass.... There really is _no_ evidence that momentum and
kinetic energy, that chemical transformations, that electrical and
magnetic phenomena, occur in the living body in any manner, or to
any extent, which differs from that obtaining in the more readily
investigated non-living world.”
In the same lecture Professor Hill replies to a statement which has
been frequently reiterated by vitalistic writers including General
Smuts and Professor Julian Huxley. Referring to the Second Law of
Thermodynamics, he says:
“Philosophically speaking, the Second Law of Thermodynamics,
dealing with the limitations of the availability of Energy, is
more liable to doubt. It is known to rest on a statistical basis,
and when we are dealing with units, complete, self-producing,
yet as invisible and intangible as the filter-passing or other
micro-organisms, it is, theoretically speaking, possible that some
means may be available of evading the statistical relations which
govern the behaviour of larger systems. But here again we must ask
for evidence--and there is none of a precise or definite character
which suggests, in the least degree, that the living cell can
escape the jurisdiction of the Second Law.”
We are thus forced to consider the order of complexity of the living
system maintained in dynamical equilibrium with its surroundings as
the essential feature which distinguishes it from non-living things.
This complexity can be arbitrarily divided into many levels; but for
convenience we may confine ourselves to two, the macroscopic and the
microscopic. Let us be explicit about the meaning of this distinction.
In the more familiar animals, we are accustomed to recognize a variety
of responses to a variety of external agencies. Generally speaking
in the more complex animals each kind of reactivity and each kind of
receptivity is spatially localized. For instance, light impinging upon
the retina evokes contraction of the pigment cells in the toes of a
frog. From this macroscopic complexity of the gross architecture of
the animal body arise two types of problems: first, the problems of
co-ordination dealing with the way in which a disturbance recurring in
some receptive area is propagated to an effector organ (gland, muscle,
etc.) in some other region; and second, the problems of metabolic
exchange, dealing with how the supply and distribution of sources
of energy for all this display of activity is maintained. The first
involves the study of the nervous impulse along the peripheral nerve
fibres and through the central nervous system; it also involves the
study of the internal secretions. The second involves the study of
digestion and assimilation of foodstuffs, the intake of oxygen to burn
up the waste products of chemical activity, and the removal of carbon
dioxide, water and other products of oxidation. In contradistinction
to the gross complexity of organs or populations of cells, we have to
take into account the microscopic complexity of the cell itself. This
presents a more general issue, because there exist many organisms whose
complexity is of the same order as that of the separate cells which
make up the bodies of familiar animals of visible dimensions. Two of
the major problems of cell physiology concern the way in which the cell
maintains its semi-permeability, and the way in which it maintains
a constant renewal of chemical materials by utilizing the energy
liberated in certain organic oxidations.
If we remove the magneto from a car, we can keep it intact for an
indefinite period: it is fundamental to our idea of a mechanism that it
can be taken to pieces and put together again. We are so accustomed to
think of a leg or an arm as dependent for their activity on the rest
of the body, that the conception of a living mechanism is repugnant to
common sense. In the laboratory it is possible to study properties
of nerve, muscle, the cell membrane, absorption of food in the gut,
oxidation of nitrogenous materials in the liver, etc., as isolated
events. A person who is not a biologist almost invariably expresses
bewilderment when he sees the isolated heart of an animal beating
regularly in a perfusion apparatus. There exists the idea that the
living organism differs from a mechanical system in that the parts
cannot persist without the whole.[4] Behind this illusion of common
sense the holistic concept of adaptation stands securely entrenched.
The holistic conception implies that for living systems the part must
be interpreted in relation to the whole, and not the whole from the
interaction of parts. We have seen that the ultimate non-biological
constituents of living matter, molecules, atoms, etc., do not behave
differently when united to form a living system. In transcending this
level of organization we are faced with an equally striking conclusion.
The contraction of an isolated muscle preparation is essentially the
same as the contraction of a muscle considered as an isolated aspect
of the behaviour of the intact organism. The passage of the nervous
impulse along an isolated nerve is not fundamentally different from the
passage of the nervous impulse in the normal animal. The conversion
of sugar into alcohol by the isolated enzyme zymase obtained from
crushed yeast cells is a process like that of the conversion of sugar
into alcohol by the living yeast fungus. The whole development of
physiology, from the time when Haller first made an isolated muscle
preparation and Spallanzani produced animal light by moistening a
dessicated powder of luminescent jelly fishes, bears witness to the
conclusion that the separated constituents of a living whole do not
at any level of complexity behave differently from the way in which
they behave as parts of a more complex order. Thus, when the fullest
recognition is given to the extreme complexity of living systems, the
problem of self-regulation submitted to experimental analysis does not
bring forward any confirmation for the holistic view of adaptation as
the creative interpolation of new irreducible properties at different
levels of complexity. The holist may reply that it is one thing to take
the living machine to pieces, and another thing to put it together
again. Even here the analogy with the machine holds good. To graft the
eye of one salamander tadpole on to the head of another individual
is now a commonplace of experimental embryology. Five-legged and
two-headed newts are now manufactured in the laboratory.
Self-regulation, the way in which an organism maintains a seeming
continuity of arrangement in spite of the uninterrupted and ubiquitous
flux of macroscopic and microscopic changes which its existence
implies, defines the sense in which the term adaptation is ordinarily
used by the physiologist. In contradistinction to this physiological
and individual use, adaptation is employed in biological discussion
in a morphological and specific sense, when we consider how one
animal comes to be distinguished from another by some architectural
arrangement appropriate to a particular kind of environment. In this
sense the problem of adaptation has played a prominent part in the
evolutionary speculations of the past century. Given the fact that
organisms are not only self-regulating but self-propagating, the
evolutionary theory sets out to explain how living systems come to
exist in so many specific forms, and how it is that these specific
forms are on the whole _fitted_ or _adapted_ to their respective
surroundings. The qualification _on the whole_ is highly significant.
Organisms display many peculiarities of architecture which by no
stretch of imagination can be regarded as necessarily fitting them
better for their conditions of life. To assume that every peculiarity
of structure in an animal is useful to it in the struggle for existence
is a pure assumption unfounded on anything but teleological prejudice.
Adaptation in the morphological sense really includes two ideas which
to some extent coalesce, and are therefore all the more readily
confused. At times the word implies nothing more than _viability_.
In this sense adaptation is the whole problem of evolution. Up to
a certain point an organism must be “suited” to its environment in
order to live at all. At other times adaptation is extended to mean an
essential utility in every detail of the structure of an organism. This
is a mischievous implication which, as will be seen later, has hindered
the formation of a clear conception of the evolutionary process.
Even if we could justify the belief that female peafowl are as much
impressed by peacocks as are some male biologists, we have still failed
to supply a criterion of survival value which has any satisfactory
significance. The enthusiast who describes an adaptation is often like
the advertizing manager who tells us how many customers we shall get,
if we advertize with him, but is inclined to be reticent about whether
the profit derived from more customers is commensurate with the fees
he proposes to exact for his services. Bateson, who first applied
Mendel’s principles to animals, wrote five years before the Mendelian
Renaissance in terms which may still be commended to the thoughtful
examination of every student of the evolutionary problems:
“Whereas the only possible test of the utility of a structure is
a quantitative one, such a quantitative method of assessment is
entirely beyond our powers. To know that the presence of a certain
organ may lead to the preservation of the race is useless, if we
cannot tell how much preservation it can effect... unless we know
also the degree to which its presence is harmful, unless, in fact,
we know how its presence affects the profit and loss account of the
organism.” (_Materials for the Study of Variation_).
That animals do in fact display many structural characteristics which
are in no sense useful to them is generally admitted to-day. It
thus becomes as much the function of any theory of the evolutionary
process to explain the origin of useless as to explain the origin
of useful devices. There is a practical limit to the use of the
concept of adaptation in morphology. There is a no less obvious limit
to the use of the concept of adaptation in physiology. An animal
is a self-regulating system up to a point; but it cannot in every
contingency take arms against a sea of troubles and by opposing end
them. If we could define in some general terms where this limit lies,
we should be justified in speaking of a principle of adaptation in
the sense that we speak of a principle of conservation of matter.
The ideally self-regulating unit of living matter endowed with the
secret of perpetual youth is as imaginary as the Economic Man. At
present the fact that organisms cease to regulate themselves and die
is as fundamental a problem of biology as the converse fact that they
regulate themselves and thereby continue to live. The fact that the
organism has a good deal of useless anatomical equipment seems to be
as true as the fact that on the whole its anatomy is suited to the
requirements of its surroundings. In whichever way we employ the term
adaptation we are forced to the conclusion that it is only legitimate
to speak of a principle of adaptation in the sense in which we speak
of the active principle of the thyroid gland. Adaptation defines a
field of problems which await solution. In that sense the concept of
adaptation is as fundamental to mechanistic as to any other theories of
the organism.
§3
This is not what is generally meant when it is said that adaptation
is a fundamental principle of biological enquiry. I believe that it
is the only legitimate sense in which it can be said that there is
a biological principle of adaptation. It seems to me that, when we
go further and put more than this into our concept of adaptation, we
are driven to formulating the problems of biology in a wrong way. By
inventing hypotheses to explain facts which do not exist, we then
proceed to give false interpretations of the significance of facts that
do exist.
When the principle of adaptation is treated as a principle which
enables us to predict conclusions, it constantly leads us to fantastic
distortions of what really happens. If I wished to illustrate this in
connexion with the self-regulating aspect of the concept of adaptation,
I could not do better than refer to current speculations about the rôle
of the ductless glands in the economy of the organism. The physiologist
who interprets his field of observation in a manner analogous to
that of the physicist and chemist realizes that we have no reason
to believe that every chemical entity found in the animal body is
necessary or even useful to its owner. He will not therefore draw any
conclusions of a far-reaching nature from the discovery that a certain
tissue extract has highly specific physiological properties, unless
he can show that the removal of the tissue itself produces effects
of an opposite nature to those which ensue on injecting its active
constituent. The student of ductless glands who regards adaptation as
a principle to be applied rather than as field to be explored will
not be held back by such restraint. We must thank the “principle” of
adaptation in endocrinology for the romantic guess-work of that school
which undertakes to interpret the whole of human history in terms of a
glandular explanation of temperament. Most speculations on which the
glandular theory of temperament are based have their only experimental
basis in the presence of supposedly specific active substances in one
or other tissue extract. A “principle of adaptation” does not assist
us to understand why the pituitary gland of a fish should contain one
specific constituent which produces expansion of the black pigment
cells in the skin of a frog, another specific constituent which causes
the uterus of the mammal to contract, and yet a third which produces
a specific fall of blood pressure in the bird and a specific rise of
blood pressure in the mammal.
It is especially in the field of evolutionary biology that we must look
for most guidance, because the concept of adaptation has occupied such
a prominent part in the evolutionary controversy. As an example of how
“the principle of adaptation” leads to incorrect conclusions I need
cite only one example from an exceedingly able and provocative address
of Professor D. M. S. Watson.
“It is not unusual for a student of fossils to discuss the habits
of an extinct animal on the basis of a structural resemblance of
its ‘adaptive features’ with those of a living animal and then to
pass on to make use of his conclusions as if they were facts in
the discussion of an evolutionary history or of the mode of origin
of a series of sediments. In extreme cases such evidence may be
absolutely reliable: no man faced with an ichthyosaur so perfectly
preserved that the outlines of its fins are visible can possibly
doubt that it is an aquatic animal, and such a conclusion based on
structure is supported by the entire absence of ichthyosaurs in
continental deposits of appropriate ages and their abundance in
marine beds. But if extremes give good evidence, ordinary cases are
always disputable. For example, there is, so far as I know, not the
least evidence in the post-cranial skeleton that the hippopotamus
is aquatic; its limbs show no swimming modification whatsoever, and
the dorsal position of the eyes would be a small point on which to
base assumptions. Most palæontologists believe that the dentition
of a mammal, and by inference also that of a reptile or fish, is
highly adaptive, that its character will be closely correlated with
the animal’s food, and that from it the habits of an extinct animal
can be inferred with safety. Here again the extreme cases are
justified, the flesh-eating teeth of a cat and the grinding battery
of the horse are clearly related to diet. Crushing dentitions, with
the modification of skull and jaw shape and of musculature which
go with them, seem equally characteristic. I had always believed
that the horny plates and the jaws of Platypus were adapted to
hard food, and that that animal possessed them, whilst the closely
allied Echidna was toothless, because it was aquatic and lived in
rivers which might be expected to have a rich molluscan fauna which
could serve as food. But the half-dozen specimens whose stomachs I
have opened contained no molluscs whatsoever, and seem to have fed
on insect larvæ, the ordinary soft bottom fauna of a stream.” (_Op.
cit._)
We are now beginning to see that the evolutionists of the nineteenth
century focused their attention far too exclusively on adaptation. In
other words, they regarded adaptation as a principle like the principle
of conservation of matter, one of universal validity within the field
of biology. Any theory of evolution has to explain why non-adaptive,
as well as adaptive, features arise. In that sense the fundamental
problem of evolution is not the origin of adaptation but the origin of
species. Both the theories of Lamarck and Darwin implicitly assumed
that the differences between species, in the traditional, i.e. Linnæan
sense, are mainly utilitarian. Having started with an incorrect
apprehension of the facts they proceeded to elaborate hypotheses to
account for them. Thence inevitably they drew from these hypotheses an
unsatisfactory account of the way in which new species do arise. From
the modern standpoint analysis of the species problem does not demand a
recognition that species differences are even in the main utilitarian,
though such a statement would probably be true of differences between
larger units such as genera. Nor from the modern standpoint do the
hypotheses of either Lamarck or Darwin give us any clue to the way in
which the species barrier, i.e. inability to breed with other species
successfully, can have arisen. Anything which remains of the Lamarckian
principle in the light of modern research has no special relevance
to the origin of adaptations. Whatever remains of the theory of
natural selection has been completely divested of the implication that
non-adaptive characters were necessarily adaptive at their inception.
A discussion of the fate of the Lamarckian and Darwinian theories must
be undertaken elsewhere. Here it is sufficient to point out that both,
more particularly the latter, had a peculiarly sterilizing influence
on the growth of experimental biology. Obsessed with the principle of
universal adaptation which Natural Selection had secularized, zoology,
from the publication of the _Origin of Species_ to the rediscovery of
Mendel’s Laws, wandered for forty years in a wilderness of phylogenetic
speculation. Biological research in the words of Professor Punnett
became
“devoted to the construction of hypothetical pedigrees suggesting
the various tracks of evolution.... The result of such work may be
said to have shown that the diverse forms under which living things
exist to-day, and have existed in the past, so far as palæontology
can tell us, are consistent with the view that they are all
related by the community of descent.... It is obvious that all this
work has little or nothing to do with the manner in which species
are formed.”
According to the Selectionist doctrine in its original form, characters
originated and persisted in virtue of their utility and what Darwin
somewhat vaguely called “the strong principle of inheritance.” To
explain any peculiarity of structure or habit, it became necessary
only to show one of two things, either it was useful to its owner or
was once useful to an ancestor of its owner. Everything was or had
been an adaptation. This resulted in a complete divorce of comparative
anatomy from comparative physiology. The morphologist and systematic
zoologist regarded it as an impertinence of the physiologist to seek
for experimental evidence, where a perfectly good case of adaptation
was evident to anyone who would accept their premisses.
I will illustrate this from a field in which I have myself carried out
experimental investigations for twelve years. Writing of colour change
in frogs Dr. Hans Gadow makes the following remarks in the _Cambridge
Natural History_ (_Amphibia and Reptiles_, p. 36):
“Biedermann concludes that the chromatic function of frogs in
general depends chiefly upon the sensory impressions received by
the skin, while that of fishes depends upon the eye. All this
sounds very well, but the observations and experiments are such
as are usual in physiological laboratories, and the frogs, when
absorbed in their native haunts, or even when kept under proper
conditions, do not always behave as the physiologist thinks they
should. There is no doubt that in many cases the changes of colour
are not voluntary but reflex actions. It is quite conceivable that
the sensation of sitting on a rough surface starts a whole train of
processes: roughness means bark, bark is brown, change into brown;
but one and the same tree frog does not always assume the colour of
the bark, when it rests or when it sleeps upon such a piece. He
will if it suits him remain grass green on a yellow stone or on a
white window frame.... The sensory impression received through the
skin of the belly is the same, no matter if the board be painted
white, black or green, and how does it then come to pass that the
frog adjusts its colour to a nicety to the general hue or tone of
its surroundings.”
It is safe to say that no one, unless at the outset prejudiced by the
principle of adaptation, could be led to entertain the view that frogs
as a rule are able to adjust themselves “to a nicety” to the general
hue and tone of their surroundings. The state of the pigment cells in
the skin is influenced independently by a number of diverse factors,
including moisture, temperature, diffuse light acting on the skin
and reflected light acting on the retina of the eye in the opposite
sense. Individual frogs differ in basic pattern, but the range of hue
between the dark and pale condition for any frog is fixed, as is also
true of the proverbial chameleon. When the conditions affecting colour
change in a frog are defined, it is possible to predict the pigmentary
response of a frog and its time relations with as much confidence as
any other physical event in nature. It is, on the other hand, quite
impossible to draw any far-reaching conclusions about colour change
from uncontrolled observation of the frog in its native haunts, because
the number of significant variables is far too numerous to handle
in this way. I have quoted this passage to show the attitude which
zoologists under the influence of the post-Darwinian tradition adopted
towards experimental enquiry of any description. Dr. Gadow applies
the “principle of adaptation,” as it was then used in morphology, to
the self-regulating aspect of the organism with results which show
what might well happen to physiology if the physiologist employed
the principle of adaptation as the chemist employs the principle of
conservation of matter.
Ecology, or the study of the relation of species to particular types
of environment, provides a clear illustration of the progress that
has been achieved by detailed study of physiological mechanisms in
place of the speculative application of the principle of “adaptation.”
Krogh and his pupils have made a special study of the physico-chemical
properties of the blood pigments of the lower organisms, and have
thereby thrown a good deal of light on the conditions which determine
their ecological distribution. Let us take the case of two common bony
fishes, the carp and the trout. It is a matter of common experience
that in nature the trout will only live in running streams. It can
be kept with great difficulty in aquaria, if special precautions for
aerating the water are taken. The carp will live in still water, where
the oxygen content is low, and like its ally the goldfish accommodates
itself to the aquarium with great ease. The difference between the two
types is at once understood, when we know that the hæmoglobin of the
carp has a much higher affinity for oxygen than the hæmoglobin of the
trout. In consequence the blood of the carp is completely saturated
with oxygen when the oxygen content of the water in which it swims is
far below that which is in equilibrium with the oxygen pressure of the
atmosphere. The blood of the trout on the other hand is only fully
saturated with oxygen when the water is itself nearly saturated.
The concentration of salts in the blood of fishes like the trout
and carp is kept constant at a level below that of sea water. The
concentration of dissolved substances in the blood of sharks and
dogfishes which are all marine is in equilibrium with the osmotic
pressure of the sea. The respiratory centre of the wrasse is
paralysed at 60° C. {sic}, while the heart of the English dogfish
shows irreversible changes above 18° C. Taking these facts together
we can deduce a good deal about the viability of a species in a given
locality. A fish like the skate placed near the estuary of a large
river is forced to remain where the salt concentration is above a
certain level. A salmon is not subject to this restraint. Assuming that
the fish can pass the estuarine boundary and proceed upstream, two
alternatives present themselves. He can remain in the swiftly moving
main stream or take to backwaters and stagnant lakes connected with
it. If he has the hæmoglobin of a trout, he is committed irretrievably
to the former alternative. Being compelled to remain in the swiftly
running part of the river bed, he might stay in the lowlands or make
for the source, which in general will be much colder. In the case of
a fish like the wrasse, whose respiratory centre is paralysed at a
temperature of 6° C., the latter course is impossible, if the river
rises in a high range. Thus in place of vaguely speculating about how
an organism is specially “adapted” to live in some particular place,
experimental biology is gathering clearly defined ideas about why an
organism cannot live in any place other than that in which it does live.
The idea that a problem can be solved by invoking the principle of
adaptation assumes its most grotesque form in Haeckel’s discussion of
Recapitulation. The classical example of what is called recapitulation
is provided by the gill clefts of vertebrates. All vertebrate
embryos have pits or clefts at the sides of the throat, supplied by
a characteristic arrangement of blood-vessels. In fishes the clefts
acquire filaments richly supplied with blood-vessels, and act as
gills. Both the gill clefts and the characteristic arrangement of
blood-vessels associated with them persist throughout life. In frogs
and salamanders gill filaments are developed in the tadpole stage, but
the clefts disappear in adult life and the characteristic arrangement
of their blood supply becomes profoundly changed. In Man and most land
vertebrates the gill clefts are never used as respiratory organs, and
with their blood-vessels disappear at an early stage in development.
During the first half of the last century Van Baer, the pioneer
embryologist, propounded a generalization which may be stated thus:
embryos of different species of animals of the same group are more
alike than the adults, and the younger the embryo the greater are the
resemblances. This generalization, well illustrated by the gill clefts,
was later extended by Haeckel with the sonorous title “Biogenetische
Grundgesetz.” It is thus defined by its author: “The history of the
fœtus is a recapitulation of the history of the race, or in other
words, ontogeny is a recapitulation of phylogeny.”
The way in which the modern geneticist handles the problem of
development offers a striking contrast to the attitude of Haeckel and
a generation of zoologists unduly preoccupied with the concept of
adaptation. A recent investigation from the laboratory of Professor
Julian Huxley will illustrate the difference. In the little crustacean
_Gammarus_ there are a number of varieties distinguished by the colour
of their eyes. All coloured eyes are at an early stage of development
colourless. They then become scarlet owing to the formation of a red
pigment. They may subsequently darken owing to the deposition of the
black substance known as melanin. Varieties with eye colour from a
dark red through various grades of chocolate to dark brown and black
are distinguished by the time at which the deposition of melanin
begins and the rate at which it occurs. Here there is no difficulty in
seeing what conditions must be fulfilled in order that a new variety
should or should not recapitulate the characteristic of the ancestral
stock from which it arises. If a red-eyed variety of Gammarus arose
from a white-eyed stock, it would necessarily exhibit the ancestral
condition at the beginning of development, because all eyes are at
first colourless. If a black-eyed form arose as a sport from a red-eyed
stock, it would also recapitulate the ancestral characteristic, because
all black eyes are at first red. If a white-eyed form arose as a sport
in a red-eyed stock, or a red-eyed form emerged from a black-eyed
stock, in neither case would the ancestral condition be manifest at any
stage of development. There is no question of the intrinsic usefulness
of a new character involved in this. Whether recapitulation does or
does not occur here depends upon whether the Mendelian factor which
distinguishes a new variety hastens or retards some feature of the
developmental process.
Now Haeckel’s “Grundgesetz” implies an additional statement to that
contained in Van Baer’s Law. It signifies that the embryonic stages of
one form are to be compared with adult rather than embryonic stages
of another. This in fact is not correct, as the classical cases of
recapitulatory phenomena demonstrate most clearly. The mammalian
embryo never possesses true gills. It goes through a stage at which it
has the characteristic clefts and arterial arches which in the _fish
embryo_ precede the development of functional gills. This is also
true of crustacean larvæ. _Sacculina_, the crab gall, passes through
the two characteristic larval forms of the true _barnacles_. It has
no resemblance to an adult barnacle in any stage. A more serious
objection to Haeckel’s way of stating the idea of recapitulation in
development is the vagueness it assumes when brought face to face with
the exceptions that are as numerous as the applications of the rule. An
illustration of the exceptions is provided by eye colour in the human
species. It is fairly certain that the blue-eyed condition has arisen
as a mutant in a brown-eyed stock; yet the eyes of brown-eyed adults
are often blue in the newly born.
It is not difficult to discover in Haeckel’s own writings the train of
reasoning which led him to distort the facts of development in stating
the law which is often associated with his name.
“The evolution of the fœtus (or ontogenesis),” states Haeckel, “is
a condensed and abbreviated recapitulation of the evolution of the
stem (or phylogenesis); is preserved by a constant heredity; on the
other hand, it becomes less complete in proportion as a varying
adaptation to new conditions increases the disturbing factors in
the development (or cenogenesis). The cenogenetic alterations or
distortions of the original paligenetic course of development take
the form, as a rule, of a gradual displacement of the phenomena,
which is slowly effected by adaptation to the changed conditions
of embryonic existence during the course of thousands of years.
This displacement may take place as regards either the locality or
the time of the phenomenon. The first is called heterotopism, the
second heterochronism.”
So naïve a combination of garrulous teleology and self-contradiction
is characteristic of the hopeless confusion of thought which existed
in evolutionary biology, while it remained dominated by the principle
of adaptation. The larval “adaptations” should on the face of it
recapitulate their ancestral story--and so on in endless regression.
There is no intelligible meaning in Haeckel’s explanation of the
admittedly ubiquitous exceptions to his rule.
Haeckel’s so-called Biogenetische Grundgesetz exerted a profound
influence on biology during the second half of the nineteenth
century, and perhaps did more than anything else to divert zoologists
from the study of activity to the pursuit of insignificant details
of no conceivable physiological interest. Instead of furthering
the development of zoology as an exact science, it substituted
the construction of architectural mnemonics for the search after
quantitative laws. With Haeckel’s law is associated an interesting
logical fallacy in the development of the argument for evolution.
Huxley made a good debating point when he disclosed the embarrassing
information that a bishop at one stage of the episcopal life cycle
has gill structures like those of a fish. From the standpoint of
formal logic the point is worthless. Only the atmosphere of religious
propaganda which surrounds the birth of the evolutionary doctrine
can explain the perennial reappearance of the contention that
recapitulation constitutes an argument _sui generis_ in favour of the
doctrine of descent. If experimental breeding taught us that mutant
forms recapitulate the characteristics of the stock from which they
originate, the resemblance of developmental stages of present-day
forms to adult organisms which existed in the geological past would
constitute a special consideration in favour of regarding fossil
remains as ancestral to contemporary animals. As yet experimental
breeding teaches us no such thing. We do not find that a white-eyed fly
originating as a sport in a red-eyed stock invariably has red eyes at
any prior stage of development. Recapitulatory phenomena are difficult
to explain on a theological basis, but they do not constitute a special
argument in favour of the evolutionary alternative. To-day biologists
are beginning to realize that evolution must furnish an explanation
of specific differences which are not adaptive as much as specific
differences which are adaptive. With this change of outlook it is
becoming possible to discuss the logical status of the evolutionary
hypothesis without recourse to arguments which belong more properly to
propaganda than to science.
PART II
DARWINISM AND THE ATOMISTIC INTERPRETATION OF INHERITANCE
SUMMARY
The failure to recognize that biology no less than physics is
an ethically neutral science is a heritage of the evolutionary
controversy. The doctrine of organic evolution evoked intense religious
hostility in the middle of the nineteenth century. Biologists were
compelled to fight for their right to speculate on their own lines.
Forced into the forum as a propagandist the biologist gave less
attention to the logical structure of the new theory than to its
apparent implications for social philosophy. The ethical concept of
progress became entangled in the evolutionary idea. In the writings of
Herbert Spencer and the evolutionist philosophers Darwinism has left a
lasting impress upon contemporary thought. Experimental biology in this
generation has undertaken the task of reducing the problems of organic
evolution to an exact science. This must necessitate a re-examination
of many traditional biological concepts and many philosophical and
sociological inferences which have been extracted from an earlier phase
in the development of the evolutionary doctrine.
V. THE METHODOLOGY OF EVOLUTION
“Chemistry is not so far from physics as the generation before ours
thought. Biology, through bio-physics and bio-chemistry, no longer
stands aloof from the methods and procedures of physical science.
And these new alliances cannot be made without modifications in
the logical construction of the separate concepts upon which these
various sciences previously took their stands. This is a task which
laboratory practice alone cannot undertake.”--_Dorothy Wrinch_
§1
From Aristotle to our own time biologists have been too preoccupied
with collecting information about the extremely complex phenomena which
they study to pay very much attention to the logical structure of the
hypotheses they adopt. This not only tends to make controversy between
the mechanist and vitalist barren, but also explains why much that has
recently been written and said about evolution is both unsatisfactory
and perplexing to the intelligent layman. Many of the views which
gained well-nigh universal assent among biologists in the latter half
of the nineteenth century have been undermined by the discoveries of
the Mendelian renaissance. When the onlooker asks the biologist for a
straightforward exposition of the present status of the evolutionary
hypothesis, he is frequently met with the guarded statement that
biologists are no longer so sure that they know _how_ evolution
occurred, but are more certain than ever that it _has_ occurred. Such
a statement might conceivably have a logically admissible meaning,
though if so, it belongs to the category of things which were better
said otherwise. On the face of it, the layman has very good reason for
wondering whether it means anything at all. It is logically permissible
to say we know that common salt is soluble, but we do not know how it
happens that common salt should possess this property. But evolution is
not a simple property. It is a process. We cannot very well know of the
existence of a process unless we can say in what the process consists.
The doctrine of evolution which deals with the way in which living
matter has come to exist in the manifold forms which biologists call
species is one which can only be placed on the same footing as the
great generalizations of physics and chemistry, when it is examined
from the experimental standpoint. From that standpoint the particular
phase in the growth of the evolutionary hypothesis associated with the
names of Darwin and Wallace has less significance than is customarily
attached to it. From a purely experimental point of view Darwin and
Wallace brought to bear on the discussion of the evolutionary doctrine
nothing which their predecessors Buffon, Erasmus Darwin, Lamarck, St.
Hilaire, Goethe and Oken lacked. The importance of their work lies in
the history of the controversy. Under Cuvier’s influence biology had
turned away from premature speculation to industrious study of the
nature of species differences from every available standpoint. Darwin
and Wallace brought together the fruits of the progress resulting
from a generation of intensive research on such lines, and formulated
the evolutionary problem in a much more explicit form than _les
philosophes_ were in a position to do. The particular answer that they
gave to the problem they formulated is the least significant part of
the contribution which Darwin and Wallace made to biological science.
The biological world did not begin to examine the experimental
implications of the selectionist solution until the rediscovery of
Mendel’s laws by Correns, de Vries and Tschermak, and their extension
to animals by Bateson and Cuenot in the opening years of the present
century. The Mendelian renaissance provoked considerable hostility from
a generation of biologists untrained in experimental methods. It is
only now becoming possible to re-examine the selectionist doctrine with
detachment and candour.
It must not be implied that antagonism to the new movement was a mere
disinclination to face the effort of learning new methods of attacking
the problem. In the nineteenth century biologists had to fight for
their right to speculate freely in their own field. The generation in
whose memory the struggles of that period were fresh not unnaturally
resented the suggestion that biologists were no longer unanimous among
themselves. It was heresy to betray the policy of a united front. If
such schisms were permitted, and the truth were allowed to leak out
to the general public, the church somnolent might again become the
church militant. The recently published biography of the late William
Bateson shows how keenly this was felt. In the end hostility towards
the new movement which followed the rediscovery of Mendel’s work gave
place to a comfortable compromise, based on the attractive device of
inventing a word for human ignorance. This device is not peculiar
to biological science. There were from the start physicists who
entertained the most profound suspicion of the ether on that account.
It was agreed to state that inheritance in animals and plants is of
two kinds, Mendelian and non-Mendelian. Study of the former was to be
encouraged because it was useful to stock breeders, horticulturalists,
and pigeon fanciers. The latter was the peculiar speciality of the
evolutionist. Apart from that, the impenitent selectionist did not
attempt to define exactly what non-Mendelian inheritance was. Its
sphere was progressively encroached upon by the Mendelian variety,
until nothing was left of it but a comfortable corner for those highly
variable characters which were somewhat vaguely referred to under the
term “quantitative inheritance,” i.e. hereditary differences in size so
subject to fluctuating variability in response to external conditions
that they are only definable by reference to a statistical average for
a particular inbred stock. Naturally experiment first turned to the
analysis of clear-cut hereditary differences such as colour, where
little trouble is requisite in standardizing external conditions, so
that an hereditary difference will be apparent in the individual. Since
mathematical analysis has been brought to bear on the study of size
inheritance in such work as that of East and Jones, there can no longer
be any justification for doubting that the atomistic conception of
heredity which Mendel formulated covers the whole domain of biparental
inheritance.
While experimental analysis was progressing towards a recognition of
the universal validity of the Mendelian conception, the brilliant
work of Morgan’s school was leading to an exact theory of the
inter-relation of genetical factors based on the observed behaviour
of the chromosomes. Experiment now equipped with a definite criterion
of genetic purity could assert that new forms do come into existence
discontinuously in nature. It could state the conditions which
determine whether a new genetic character will persist. When chromosome
maps of several allied species of the fruit-fly were constructed by
Metz and Sturtevant seven years ago the whole discussion of the problem
of species formation entered on an entirely new phase. To-day we must
approach the discussion of evolution on the assumption that in Mendel’s
atomistic conception of the hereditary process must be sought the
correct interpretation of how new characters, having come into being,
may be transmitted to future generations.
§2
To appreciate at once the greatness and the limitations of Darwin’s
contribution to evolutionary thought it is essential to see the
question in its historical perspective. Many of the steps which have
led to the construction of the evolutionary hypothesis are now only
of historical interest. Only with an understanding of the history
of the doctrine is it possible to gain a clear idea of the logical
status it occupies in scientific thought. In approaching it, one has
to remember that the discussion of organic evolution aroused a good
deal of prejudice from religious quarters, and that in consequence
many issues, e.g. Recapitulation, which were not strictly relevant to
a straightforward presentation of the problem occupied a prominent
place in the controversies that raged around it. In forming an estimate
of the present status of the evolutionary hypothesis, let us, as far
as possible, eliminate these irrelevant questions, and deal only with
the steps which have made a definite constructive contribution to the
present state of knowledge. These may be treated under four headings:
(_a_) The Principle of Biogenesis, (_b_) The Principle of Unity of
Type, (_c_) The Principle of Succession, and (_d_) The Principle of
Genetic Variation.
_The Principle of Biogenesis_ is simply the recognition that animals
and plants only arise in our immediate experience from other animals
and plants through the process of reproduction. Linnæus accepted
it in his doctrine of the fixity of species as generally true with
regard to animals in the ordinary sense. Not until the middle of the
nineteenth century did the work of Pasteur demonstrate its validity
for micro-organisms. Linnæus and Ray were among the first to recognize
the general truth of the commonplace that “like begets like.” The
Aristotelian influence which predominated during the Renaissance
had lingered on until the beginning of the seventeenth century. The
fascinating legend of the goose barnacle contained in the concluding
passage of Gerrard’s _Herbal_ (1594) is illustrated by an actual
woodcut of the Goose and its Barnacle Progenitor. The passage reads:
“But what our eyes have seene; and hands have touched we shall
declare. There is a small Island in Lancashire called the Pile of
Foulders, wherein are found the broken pieces of old and bruised
ships, some whereof have beene cast thither by shipwracke, and also
the trunks and bodies with the branches of old and rotten trees,
cast up there likewise, whereon is found a certain spume or froth
that in time breedith unto certain shells, in shape like those of
the Muskle, but sharper pointed, and of whitish colour, wherein is
contained a thing in forme like lace of silke finely woven as it
were together, of a whitish colour, one end whereof is fastened
unto the inside of the shell, even as the fish of Oisters and
Muskels are; the other end is made fast unto the belly of a rude
masse or lumpe which in time commeth to the shape of a Bird; when
it is perfectly formed the shell gapeth open, and the first thing
that appeareth is the foresaid lace or string; next come the legs
of the bird hanging out, and as it groweth greater it openeth the
shell by degrees, til at length it is all come forth and hangeth
onely by the bill: in short space after it cometh to full maturitie
and falleth unto the sea, where it gathereth feathers, and groweth
to a fowle bigger than a Mallard and less than a goose having
blacke legs and bill or beak, and feathers blacke and white,
spotted in such manner as is our magpie.... For the truth thereof
if any doubt, may it please them to repaire unto me, and I shall
satisfie them by the testimonie of good witnesses.... The bordes
and rotten planks whereon are found these shells breeding the
Barnacle are taken up on a small Island adjoyning Lancashier, halfe
a mile from the main land, called the Pile of Foulders. They spawn
as it were in March and April; the Geese are formed in May and
June, and come to fulnesse of feathers in the month after. And thus
having through God’s assistance discoursed somewhat at large of
Grasses, herbs, Shrubs, trees and Mosses, and certain Excrescences
of the earth, with other things moe, incident to the historie
thereof, we conclude and end our present Volume, with this Wonder
of England. For the which God’s Name be ever honoured and praised.”
The legend of the goose and the barnacle died a slow death, and many
diverting citations might be added. That canny Scot, Sir Robert Moray,
wrote concerning the mystery surrounding the reproductive habits of
geese and barnacles so late as 1678 in the following words, which occur
in a paper actually published in the _Royal Society’s Transactions_.
After describing the barnacle shells washed up on the coast of
Scotland, he refers to their “little bill like that of a goose, the
eyes marked, the head, neck, breast, wings, tail and feet formed, the
feathers everywhere perfectly shaped and blackish coloured, and the
feet like those of other water fowl to my best remembrance.”
Writing in the middle of the seventeenth century Sir Thomas Browne
states (_Vulgar Errors_, bk. 3):
“Concerning the generation of frogs we shall briefly deliver that
account which observation hath taught us. By frogs I understand
not such, as arising from putrefaction are bred without copulation
and because they subsist not long are called temporariæ (Rana
temporaria, the common frog), nor do I mean the little frog of an
excellent parrot green that usually sits on trees and bushes, and
is therefore called Rananculus viridis (the tree frog) but hereby I
understand the aquatile or water frog, whereof, we may behold many
millions every spring in England.”
Referring to the doubt expressed by the author of _Vulgar Errors_
concerning Aristotle’s belief that mice arise from putrefaction,
Alexander Ross commented:
“So may one doubt whether in cheese and timber worms are generated;
or if beetles and wasps in cow’s dung; or if butterflies, locusts,
grasshoppers, shell fish, snails, eels and such like be procreated
of putrefied matter which is apt to receive the form of that
creature to which it is by formative powers disposed. To question
this is to question reason, sense, and experience. If he doubt
of this let him go to Egypt, and there he will find the fields
swarming with mice, begot of the mud of Nylus, to the great
calamity of the inhabitants.”
During the sixteenth century under the influence of Vesalius, Fallopius
and Servetus experimental investigation liberated medicine from the
paralysing tradition of Galenic teleology. The effect of this change
of outlook became evident in the revival of natural history in the
seventeenth century. Redi (1688) turns to experiment to decide whether
maggots can be produced from putrescent meat, if flies are prevented
from depositing their eggs on it. “Reason, sense and experience” were
at length forced to capitulate to experiment. The comparative study of
animal life after centuries of stagnation following the publication
of Aristotle’s Natural History entered on a new phase. So long as
innumerable _ad hoc_ accounts of the origin of species existed the
general problem with which the evolutionary hypothesis deals could not
be envisaged. Thus the work of Linnæus is the starting-point of the
modern theory of evolution.
More than a century elapsed before the essential features common to
sexual reproduction in all animals were understood. Leeuwenhoek,
a Hollander, in 1668 had first seen the minute spermatozoa in the
seminal fluid. A little over a century later the ingenious Abbot
Spallanzani gave experimental proof that it is to the spermatozoan
that the seminal fluid owes its fertilizing power. Only in 1879 did
Hertwig and Fol independently observe beneath the microscope that
only one sperm normally fertilizes one egg. Their observations were
made on sea-urchins, but we now know that their conclusions are true
for all animals. Thus the recognition that everything implied in the
term inheritance has reference to the material substance of the egg
and sperm, a concept fundamental to any exact theory of hereditary
transmission, did not emerge with clarity till more than fifteen years
after the _Origin of Species_ was published.
The formal classification of organisms codified by Linnæus introduced
a new era of intensive investigation into the character of species
differences and so ushered in the great age of comparative anatomy.
Thus we come to the second step in the historical development of the
Evolution theory, the _Principle of Unity of Type_. This generalization
was the special contribution of the school of French and German
comparative anatomists whose foremost exponent was Georges Cuvier. The
work of Linnæus gave a great impetus to the study of the structural
differences between animals, at a time when anatomy like any young
branch of knowledge was still dominated by teleology. Some instructive
examples of the happy combination of piety and anatomy are given in the
_Speculum Mundi_ published by John Swan in 1635. In an old translation
of Pliny the Elder there occurs the following information about the
elephant:
“Their skin is covered with haire or bristle, no, not so much as in
their taile, which might serve them in good steade to drive away
the busie and troublesome flies (for as vast and huge a beast as he
is, the flie haunteth and stingeth him), but full their skin is of
crosse wrinckles lattiswise; and besides that, the smell thereof
is able to draw and allure such vermine to it, and therefore when
they are laid stretched along, and perceive the flies by whole
swarmes settled on their skin, sodainly they draw those cranies
and crevices together close, and so crush them all to death. This
serves them instead of taile, maine and long hairs....”
This citation is not an isolated instance of the way in which a
pagan philosopher could employ the study of natural history to
justify the ways of God to men. During the Middle Ages the influence
of ecclesiasticism reinforced the teleological attitude from which
Aristotle’s Natural History is comparatively speaking free. At a
later date Deism had its scientific complement in a tradition which
identified the pursuit of Natural History with Natural Religion. The
first classifications were based on comparatively superficial points
of resemblance. As the study of animal structure progressed in the two
generations that followed the labours of Ray and Linnæus, it became
increasingly evident that the teleological standpoint in comparative
anatomy is inadequate. If animals had been specially designed to suit
their conditions of life, it would be expected that the greatest degree
of similarity would be found in animals pursuing a similar mode of
existence. This is not what is actually found. On the contrary, as
we make the greatest degree of similarity in structure the basis of
our attempts to classify animals, our units of classification resolve
themselves into collections of forms which show the greatest diversity
of habit, locality, diet, means of progression or anything else
which might be significant from a purposive standpoint. Animals can
be classified in groups based on striking similarity in architecture
and development involving complex constellations of physiological
units. Within these groups the utmost variety of habitat, climate,
locomotion, nutrition, etc., are encountered. The underlying similarity
of the bones of the limb and its musculature in a whale, a bird and an
elephant, as contrasted with the limb structures of a beetle, a fish
or a squid illustrate this conclusion. The whole study of systematic
zoology bears witness to it. Van Baer extended the principle of Unity
of Type to embryonic forms in 1834.
The importance of the principle of Unity of Type to the Evolutionary
hypothesis lies in the attitude which it promoted. By discouraging the
teleological approach to the diversity of animal life, it paved the
way for a naturalistic investigation of the problem. The net result
of the intensive study of comparative anatomy which progressed under
the influence of Cuvier in France and Johannes Müller in Germany was
also to show that the task of classifying animals in hard and fast
categories is at all turns embarrassed by the existence of anomalous
intermediate forms like the duck-billed platypus or the worm-like
arthropod Peripatus. Thus biological thought was becoming more and more
sympathetic towards the existence of a process of species modification.
This tendency became more sharply defined as biology took the third
great step in the development of the modern theory of evolution.
This step has been called the _Principle of Succession_. When the Law
of Unity of Type first obtained recognition, many fossils were known,
but geologists had not arrived at a general agreement concerning
the order in which the various strata had been deposited nor the
magnitude of the time which their formation occupied. By the middle of
the nineteenth century the modern doctrine (“Uniformitarianism”) had
gained assent. It now became apparent from studying the distribution
of animals in space and time, that divergent forms which exist on
the earth’s surface to-day were preceded by widely distributed forms
of a more generalized type in the past. The further we go back in
the history of any group of animals, the less do we find the same
pronounced differences as are displayed by existing members of the same
assemblage. The differentiation of species is inferred from the record
of the rocks to have been a continuous process in space and time. This
doctrine in its modern form was explicitly put forward in 1855 by
Wallace.
The masterly way in which Darwin marshalled the facts at his disposal
in presenting this aspect of the case constitutes his chief claim to
have made an enduring contribution to the Doctrine of descent. From
ancient times, but more especially from the end of the seventeenth
century onwards, the hard remains of animals were discovered and
described. Shells of molluscs which only live in water were found far
inland remote from lake, river or sea. Such relics were attributed
by the current mythology of Christian countries to the deluge that
overwhelmed the contemporaries of the Noah family. Sceptics like
Voltaire, who ventured to offer more naturalistic hypotheses, were
not more felicitous in their speculations. An exception must be made
in favour of Xenophanes (B.C. _circa_ 500) and the Arab physician
Avicenna, who, it appears, recognized fossils as remains of animals
formerly alive, and saw in them evidence of the existence of oceans
where there is now only land. A giant fossil salamander which occurs
abundantly in the Upper Miocene of Switzerland, closely related to
the Japanese salamander _Cryptobranchus japonicus_, was unearthed by
Scheuchzer in 1726, and named _Homo diluvii testis_. The motto attached
to the figure reads:
Betrübtes Beingerust von einem alten Sünder
Erweiche Herz und Sinn der neuen Bösheitskinder.
This has been translated:
Oh sad remains of bone, frame of poor Man of Sin,
Soften the heart and mind of recent sinful kin.
After the Renaissance it seems that priority in the recognition of
fossils as remains of what were once living animals is due to Steno
(1699), a Danish anatomist who taught at Padua. More than a century
later, Cuvier’s monograph on fossil remains initiated the epoch
of systematic palæontology. The effect of the researches which it
initiated was not felt till the Uniformitarian doctrine, i.e. the view
that successive strata have been deposited by a continuous process,
was generally accepted, mainly through the work of Lyell (1830).
The impiety of this new geology promoted violent controversy. In
the minutes of a meeting of the Geological Society of Great Britain
in 1840, we are told that the retiring president, Dr. Buckland,
“with a look and tone of triumph pronounced upon his opponents who
dared to question the orthodoxy of the scratches and grooves of the
glacial mountains the pains of eternal itch without the privilege
of scratching” (_Hist. Geol. Soc. Lond._, p. 142). By the middle of
the nineteenth century geologists were universally convinced that
the various strata of which the earth’s crust is composed have been
laid down in orderly succession during periods of time compared with
which that occupied by the history of human society is of negligible
duration. Once this conclusion was accepted, the study of fossils
received a new impetus and progressed rapidly under the leadership of
men like Owen, Cope and his contemporaries. Students of fossils now
began to compare the characteristics of animals in different geological
epochs, and to elucidate evidences of a continuous succession of new
forms of life transmitted to posterity in the record of the rocks. Out
of their studies the principle of succession took shape.
The geological succession of animal and plant life is demonstrated by
two features of the record. Many of the more highly specialized and
successful groups of the present day are not found to have existed at
earlier periods of the earth’s history, and were preceded by forms
which are intermediate between them and representatives of surviving
groups that were already existent before them. It is also found that
the earliest members of the great groups are usually found to be of
a more generalized type of structure than existing types. Adequate
material for drawing these conclusions is provided only by forms which
have resistant structures, such as the vertebrates, shellfish and
vascular plants.
Before we can fully appreciate the continuity of the geological record,
we have to take into account the fact that the same animals are not
found in all the different parts of the globe. One group of animals
may be confined, like the kangaroos, to Australia; one group, like the
monotypic order, in which the ant-bear is placed, to South Africa. If,
then, we know that there existed in, let us say, the Chalk Age, a small
mammal which was of a type so generalized as to form a link between the
kangaroo and the ant bear, it is most important to know whether the
barriers of ocean that now separate Australia and South Africa were as
impassable in those times as they are now; or whether this architypal
mammal lived in a situation from which it could have access to both of
these promising lands of settlement for its family. We are thus led to
ask if the process of geological succession was a continuous one both
in time and space.
To answer this question demanded a comprehensive survey of the existing
distribution of animal life on the earth, perhaps the most significant
contribution that Darwin and Wallace made to the evolutionary doctrine.
In their writings the facts of geographical distribution, facts which
were very largely based on their own first-hand observations, and not
like their erroneous views upon heredity collected from the testimony
of other persons, first received critical examination. They were forced
to conclude that no amount of ingenuity could successfully interpret
the geographical distribution of animals on a purely teleological
basis. The habitat of different kinds of animals is not uniquely
determined by their special suitability for the locality in which they
occur. This statement is attested by many species that were at one
time restricted to a very definite area. When introduced into other
parts by man they have flourished phenomenally. A familiar instance
is the introduction of rabbits into Australia. The facts about the
geographical distribution of living and fossil species collected
by Darwin and Wallace resulted in an extension of the principle of
geological succession. This is especially associated with the name of
Wallace. Wallace’s law (1855) is stated briefly at the conclusion of
the memoir entitled _On the Law which has Regulated the Introduction of
New Species_. “Every species has come into existence coincident both
in space and time with a pre-existing closely allied species.”
With the statement of this law and its confirmation by more carefully
sifted and comprehensive data the positive contribution of the
nineteenth century to the development of the modern theory of evolution
ended. The picture of a progressive gradual differentiation of animal
life, as it spread over different parts of the earth in successive
geological epochs became a commonplace of the naturalistic outlook. It
remained for the Mendelian renaissance to clarify the conception of
this gradual differentiation as an outcome of the agency of natural
generation. It must be remembered that the Principle of Succession
is still only a step in the formulation of a theory of Evolution.
We have still to ascertain what is the natural process by which
this progressive differentiation has been effected. The principle
of Biogenesis forces us to look to the reproductive process for the
answer; but only experiment can arbitrate in this field. The weaving
together of principles derived from anatomy, embryology and geology
in the light that experiment throws on the nature of the reproductive
process is necessary to the completion of the evolutionary argument.
Let us now examine how much we have proved up to this point. We have
seen that animals only come into being in our immediate experience
through the agency of natural generation. We have also seen that
similarity which animals display in their hereditable properties
must be interpreted primarily in terms of the hereditability of the
properties themselves, and not in terms of a purposive agency. Finally
we have found evidence of a gradual and accumulative divergence in the
hereditable properties of animals continuing over vast geological
epochs. We have still to interpret this divergence in terms of the
only agency through which living matter in our experience is brought
into being. We are thus led to the fourth step in our argument, the
enunciation of the _Principle of Genetic Variation_.
This states the experimental fact that units of living matter with
new hereditable properties do actually come into being in the normal
operations of the process of natural generation. In using the word
_experimental_ in this connexion we lay bare a sharp divergence of
standpoint between Darwin’s generation and our own. Darwin collected
a good deal of information about the origin of domesticated plants
and animals. This seemed to his immediate successors to constitute
sufficient evidence for believing that new hereditable properties arise
in nature. The development of Mendelian analysis has shown that this
is far from certain. Unless we have studied the parent stock under
experimental conditions which safeguard its purity, we cannot be sure
that a new domesticated variety is anything more than a new combination
of genetical characters already present in pre-existing varieties. In
other words it may only have arisen through hybridization. We have now
at our disposal a clear concept of genetical purity and well-defined
methods for establishing the purity of a stock. The whole question has
been placed on a new foundation during the past three years by the
_artificial_ production of _mutants_ or sports by X-rays in pure stocks
of the fruit-fly Drosophila reared under experimental conditions.
A further discussion of the Principle of Genetical Variation with
special reference to the Selection doctrine will be undertaken in a
subsequent essay, when the possibility of building up new varieties
into the units which biologists call species will be dealt with
more fully. To return to the discussion of the logical status of the
evolutionary doctrine, we may assume that the Principle of Genetical
Variation is established. On this assumption we may state the
conclusion of the foregoing survey in the following terms. Animals with
new hereditable properties have appeared successively with increasing
divergence of type in the past history of the earth. Animals only arise
in our experience by reproduction from pre-existing animals. Animals
with new hereditable properties can arise in our immediate experience
by reproduction from pre-existing animals with different hereditable
properties. It is therefore natural to conclude that the existing
divergence of specific characteristics is the outcome of a natural
process of generation operating over long periods of geological time.
§3
Darwin’s generation was in the main satisfied with the evidence
derived from domestication. This was embodied as an _argumentum ad
hominem_ in the Selection hypothesis. The immediate effect of Darwin’s
influence was thus, as Punnett has remarked, “to divert interest from
the study of the origin of species” as an experimental issue. Zoology
and physiology became divorced in Great Britain. One resolved itself
into a Somerset House for the Animal Kingdom, tracing pedigrees on a
purely armorial basis. The other tended to develop in association with
narrowly clinical objectives, till the rise of modern experimental
zoology in the twentieth century. In the light of modern research the
Selection hypothesis presents some interesting methodological aspects
discussed elsewhere. Let us here confine ourselves to the evolutionary
hypothesis in broad outline.
There are two fundamental results of the present enquiry which must
be emphasized in any discussion of the logical structure of the
evolutionary doctrine. One is the necessity of distinguishing between
the Principle of Succession and the evolutionary hypothesis itself.
The other is the recognition that in the last resort the validity
of the evolutionary hypothesis rests on the issue of experiment.
The first of these may sound like a platitude. It is frequently
overlooked. Presumably when a biologist says we are more certain
than ever to-day that evolution has occurred, but less certain about
_how_ it has occurred, he really means that the enormous extension
of our knowledge of fossils has placed the Principle of Succession
on a much firmer foundation than it enjoyed in Darwin’s time. The
mass of new information about comparative anatomy now available is
more than ever inexplicable on a crudely teleological basis and more
than ever consistent with an evolutionary interpretation, if such an
interpretation is permissible. But evolution is more than succession.
It is the interpretation of succession in terms of genetical variation.
If experiment does not justify this interpretation, in other words if
we do not know _how_ evolution occurred, it is evident that we cannot
be more certain that it has occurred.
The critique of evolution is not exhausted by a logical analysis of
the experimental postulates of the hypothesis, because the doctrine
of succession is more than a question of fact. It also implies the
validity of current geological doctrines, whose logical status
lies outside our present enquiry.[5] What are ordinarily called
scientific hypotheses may be classified in two categories according
to the test of validity which is applied to them. They might be
called respectively _prospective_ and _interpretative_ for lack of
existing terminology which makes the distinction which is relevant
to our present object. If the consequences of one or other of a set
of hypotheses each capable of accounting for a given series of data
are uniquely capable of yielding verifiable conclusions about other
realms of our experience, we accept the hypothesis which leads us
to the new and previously undiscovered fact. We do this even if, in
the absence of the new fact, the hypothesis so verified is a _less
economical_ one than others which satisfied the original data but
do not account for the new one. By _prospective_ hypotheses I mean
hypotheses to which this test is applicable. They are such as permit
us to make verifiable predictions in other fields of experience. In
everyday language they assist us to prophesy correctly about future
events. They constitute a hierarchy of socialized beliefs. By their
aid mankind has been permitted to construct modern civilization. They
possess to a pre-eminent degree the quality of _publicity_ defined in
an earlier essay. Mendel’s hypothesis and the kinetic theory of gases
belong to this category. Some writers, among others William James, have
tended to imply that all so-called scientific hypotheses are of this
type. This is not so. There are hypotheses whose justification resides
only in the fact that they conform to the requirements of economy of
thought. Such hypotheses are accepted because alternative hypotheses
are less economical. They are incapable of yielding any verifiable
consequences which follow uniquely from them. It is these to which I
refer by the term _interpretative_ hypotheses. We construct them, not
because they are practically serviceable to us, but because they are
conformable with the intellectual requirements of a civilization which
is the practical outcome of the application of science. They share
two pre-eminent characteristics of the prospective type, economy of
hypothesis and ethical neutrality. The need for them resides in our
curiosity. They represent one aspect of the secularization of human
life and the obsolescence of animistic ideas. We construct them for
their _philosophic_ interest alone. The evolutionary doctrine belongs
to this category.
Few biologists would admit so heretical a conclusion. They would
argue that every new missing link whose discovery is almost daily
announced in the press provides verification of the predictions of the
evolutionary hypothesis. But there is a fallacy in this contention.
The discovery of missing links is not a unique consequence of the
evolutionary doctrine. It might be inferred from the Principle of
Succession, even if the evolutionary interpretation of the Principle
of Succession turned out to be incorrect. Given the experimental
postulates of the evolutionary hypothesis as established facts, the
evolutionary hypothesis does not belong to the same hierarchy of
scientific generalizations as the kinetic theory of gases or Mendel’s
Law, because as yet we are not able to predict with the aid of it any
unique consequences which can be made the issue of decisive tests.
There is an interesting consequence of these considerations, and one
which has a more comprehensive significance. Biology deals with two
kinds of relations: relations between living and non-living matter and
relations between different kinds of living matter. The Mechanistic
Conception of Life is a secular extension of experimental analysis of
the former, just as the evolutionary hypothesis is a secular extension
of experimental study of the latter. Both belong to the category of
interpretative hypotheses in the sense defined above. Why is it then
that so many prefer the luxury of scepticism concerning the first
issue, and resent the exercise of a suspicion of scepticism concerning
the second? Perhaps the answer is that evolution has already become
incorporated in the apparatus of what Robert Briffault calls custom
thought. I do not think that the physiologist who adopts the attitude
of Gallio towards the mechanistic conception of life, affecting to
despise all mere philosophy, is consistent, unless he is prepared to
dismiss the doctrine of Organic Descent in the same manner. I have yet
to meet one who does. Evolution is a philosophy.
VI. THE PROBLEM OF SPECIES
“The effect of Darwin’s _Origin of Species_ was to divert attention
from the way in which species originate.”--R. C. Punnett,
_Mendelism_
§1
In a letter to H. de Varigny dated November 25, 1891, Thomas Henry
Huxley wrote: “I shall be very glad to have your book on Experimental
Evolution. I insisted on the necessity of obtaining experimental proof
of the possibility of obtaining virtually infertile breeds from a
common stock in 1860.... From the first I told Darwin this was the
weak point of his case from the point of view of scientific logic.
But in this matter we are just where we were thirty years ago.” In
this passage Huxley explicitly draws attention to the fact that
Darwin never came to grips with the historic problem of the Origin of
Species, as it had been propounded by Linnæus. Three years later he
is writing to acknowledge the receipt of Bateson’s _Materials for the
Study of Variation_, a book which laid the philosophical foundations
of the present era of experimental enquiry into evolutionary problems.
“I see,” he notes, “you are inclined to advocate the possibility of
considerable _saltus_ on the part of Dame Nature in her variations.
I always took the same view, much to Darwin’s disgust, and we used
often to debate it.” Another thirty years passed by, and Bateson
ventured to appeal to his contemporaries for a reconsideration of the
traditional species problem in the light of the accumulated results
of investigation based on Mendel’s methods. He was rebuffed by a
veritable storm of criticism from Huxley’s followers. Evolution had
become Darwin, as geometry has become Euclid. Had Huxley been living,
it hardly seems likely that he would have taken the same side as his
devoted disciples in the controversy which ensued.
During the latter half of the eighteenth and the beginning of the
nineteenth century biological science progressed towards a clear
definition of the problem of Man’s secular origin. This progress
involved the rejection of many of the teleological concepts which had
been current since the Middle Ages. In the light of recent advances
in the study of inheritance and variation, we know that much of the
evidence which seemed adequate for an understanding of the evolutionary
process fifty years ago must be re-examined to-day and supplemented
from other sources. The final court of appeal in the case for an
evolutionary interpretation of the origin of species is experiment.
Only experiment can place the Principle of Genetic Variation, i.e.
the origin of new genetic types in the normal course of procreation,
on a sure foundation. A detailed examination of the evidence for this
conclusion is essential to a satisfactory examination of the logical
status of evolution in the light of modern knowledge. Four separate
issues suggest themselves for discussion in a critical enquiry into
the experimental evidence for the Principle of Genetic Variation.
We must first ask whether the origin of new hereditable types under
experimentally controlled conditions is an established fact. We must
then decide what natural agency ensures that new types having so arisen
will be preserved. This leads us to ask if the appearance of new types
is an occurrence of sufficient frequency to have accounted for all the
divergency of specific form that has come about in the interval of
time which geology places at our disposal. Finally we are faced with
the task of deciding how new genetic types can be segregated into the
units which biologists call species.
First let us consider the origin of new hereditable types. Thirty years
of controlled experiment on the lines suggested by Mendel’s work has
given abundant proof that from time to time there do arise in pure
stocks individuals which have entirely new hereditable properties. Such
individuals are called _mutants_ or sports, a term used synonymously
by some writers with the alternative word mutations. The word mutation
was originally employed by De Vries in a somewhat different sense from
that in which the term mutant is now used. It is preferable to avoid
perpetuating this confusion.[6] A new phase in this aspect of the
evolutionary problem has been initiated by the recent work of Müller. A
controllable agency, exposure of parents to X-rays, has been shown to
produce mutants in the fruit-fly Drosophila.
Darwin and Wallace are usually given the credit of first emphasizing
the fact of genetical variation. A careful study of their works shows
that they did not clearly apprehend the essential aspect of the
problem or realize the imperative necessity of subjecting the issue to
direct experimental test. When they spoke of variation they included
both genetical variation, i.e. the production of mutants as defined
above, and differences between parents and offspring which result from
the influence of external agencies in early development. The small
differences of which Darwin was thinking were mainly of bodily rather
than germinal origin. As such they have nothing to do with the problem
of evolution unless, as Darwin himself did, we accept the Lamarckian
doctrine. In the Introduction to the _Origin of Species_ Darwin states
his position thus: “Any being, if it vary in any manner profitable to
itself, under the complex and sometimes varying conditions on life,
will have a better chance of surviving, and thus be naturally selected.
From the strong principle of inheritance, any selected variety will
tend to propagate its new and modified form.” What he meant by the
strong principle of inheritance Darwin never states in exact terms.
Experimental knowledge was not ripe. Biology was still in the phase of
_a priori_ reasoning from “common-sense” principles. That he did not
distinguish between bodily and germinal differences is shown by the
following passage from Chapter 3 of the _Origin of Species_:
“_Variations, however slight, and from whatever cause_ proceeding,
if they be in any degree profitable to the individuals of a
species, in their infinitely complex relations to the individuals
of a species... will tend to the preservation of such individuals
and will generally be inherited by the offspring. The offspring
also will have a better chance of surviving, for of the many
individuals of a species which are periodically born, but a small
number can survive. _I have called this principle, by which each
slight variation if useful is preserved, by the term Natural
Selection._”--(Italics inserted.)
§2
The second aspect of the problem of genetical variation, formulated
above, is the special issue raised by the selection hypothesis of
Darwin and Wallace. Mendel might perhaps more justly be given priority
for clearly envisaging the essence of the problem.
“Those,” wrote Mendel, “who survey the work done in this department
will arrive at the conviction that among all the numerous
experiments made not one has been carried out to such an extent
and in such a way as to make it possible to determine the number
of different forms under which the offspring of hybrids appear, or
to arrange these forms with certainty according to their separate
generations or definitely to ascertain their statistical relations.
It requires indeed some courage to undertake a labour of such
far-reaching extent. This appears, however, to be _the only right
way by which we can finally_ reach the solution of a question the
importance of which cannot be overestimated in connexion with the
history of _the evolution of organic forms_.”
Mendel’s method shows us that so long as they attain sexual maturity
and bear offspring, new forms having once arisen, transmit their
hereditable properties unchanged. The new hereditary type will sooner
or later appear among subsequent generations in its original purity.
This prompts us to ask what chance a given mutant has of surviving to
sexual maturity. The question demands serious consideration. We know
that a very small percentage of animals that are born into the world
do actually survive till the age at which reproduction is possible. It
has been calculated that if all the progeny of a single female aphis
(the green plant louse) survived in every generation the total of
individuals produced in twelve generations would be 10^{22}. Since a
single aphis is about a tenth of an inch long, this number would cover
the face of the globe. Twelve generations in a family of aphids would
appear in less than three years. Evidently the chance that a given
mutant will survive depends on two things. One is whether it possesses
any characteristics which favour its survival in preference to the
parent form. The other is whether it appears once or many times in the
same stock. We now know that the same mutants appear again and again.
There seem to be definite _loci of instability_ on the chromosomes.
Which of these two considerations is of greater importance is at
present problematical. Most biologists incline with good reason to
regard the former as more significant. The significance of the second
is increasingly realized.
Many contemporary authors use the term Natural Selection to imply
that competition for the means of existence permits some mutants to
live, and weeds out others. On grounds of priority this can hardly be
regarded as justified by the writings of the Selectionist writers of
the nineteenth century. It is not supported by the actual words Darwin
used to define the term Natural Selection which he himself introduced.
Goodrich in his admirable book entitled _Living Organisms_, makes the
following statement with regard to Darwin’s position:
“It is often said that of late years Darwinism has lost ground,
and that natural selection cannot be regarded as a satisfying
explanation of, or even as an important factor in, the process of
evolution. Doubtless there is some truth in the saying, at all
events in so far as it appears that the doctrine is not what some
misguided enthusiasts may have represented it to be, that it does
not explain everything, that many problems remain unsolved. Yet
the Darwinian theory still stands unassailable as the one and only
rational scientific explanation of evolution by ‘natural’ forces
whose action can be observed, tested and measured. Nevertheless,
the critics are quite right in demanding convincing evidence for
every step in the argument. The modern developments of the study of
hereditary and variation on Mendelian lines, far from weakening the
case for natural selection, seem to have definitely disposed of the
only rival theory, the doctrine of Lamarck, founded on the supposed
‘inheritance of acquired characters.’ Fortuitous changes in the
inherited organization, in the complex of factors transmitted, are
left as the only elements of primary importance, the only stones of
which the edifice is built.”
These remarks imply that Darwin’s successors went much further than
Darwin in asserting the creative, preservative, accumulative and
continuous character of the selection process. This is true; but Darwin
himself, in the _Origin of Species_, expressly stated what he meant
by Natural Selection in two quotations which have already been given;
and neither of these agree with what Goodrich or any modern geneticist
means when he says that he believes in natural selection. Since Darwin
introduced the term he has priority in defining its meaning. If later
biologists mean something different, when they speak of natural
selection, it would avoid confusion to coin a new term. Elsewhere
Goodrich says: “What selection alone can do is to preserve variations;”
and he quotes Darwin’s words in support. Darwin meant by _preserving_
variations something different from what a modern geneticist believes.
The modern geneticist believes that _individuals_ who possess certain
advantageous characters will survive in virtue of these advantages.
Darwin and Wallace meant that _hereditary characteristics could only
survive_ if the supposed tendency to dilution of characters by crossing
were counteracted by the elimination of individuals at the other end of
the scale of variability.
Apart from what Darwin himself said on the subject we owe some
consideration to the sense in which his contemporaries understood his
argument. Since I may be accused of tilting with a lance of straw at
a windmill of my own construction, let us refer to the section on
swamping in Wallace’s _Darwinism_. “He (Darwin) had always considered
that the chief part and, latterly, the whole of the materials with
which natural selection works was afforded by individual variations
or that amount of ever-fluctuating variability which exists in all
organisms and in all their parts...” Wallace then proceeds to quote
Romanes as saying that “if a sufficient number of individuals were thus
simultaneously and similarly modified, there need no longer be any
danger of the variety becoming _swamped by inter-crossing_.” Wallace
himself wrote as follows:
“I have already shown that every part of an organism in common
species does vary to a very considerable amount in a large number
of individuals and in the same locality; the only point that
remains to be discussed is whether any or most of these variations
are ‘beneficial.’ But every one of these consists either in
increase or diminution of size or power of the organ or faculty,
that varies.... If less size of body would be beneficial, then as
half the variations in size are above and half below the mean or
existing standard of the species, there would be ample beneficial
variations.”
The implication is that natural selection by cutting off the other
half--the ample non-beneficial variations--prevents the swamping of the
beneficial ones out of existence. We know to-day that the traditional
belief in the swamping effects of intercrossing is false. With its
rejection the _argumentum ad hominem_ which made the struggle for
existence an essential agency for preserving new hereditary properties
becomes unnecessary.
However much importance Darwin himself attributed to this aspect
of his theory of Natural Selection, he makes clear his attitude in
several passages. It cannot be doubted that the assent which he
received from his contemporaries was in large measure due to it.
Accepting the prevailing misconceptions about swamping, he showed how
an evolutionary process could and, as it then appeared, must operate.
Experimental evidence for the hereditability of the kind of variations
on which Darwin seems to have relied was not brought forward. We now
know that the kind of variations which Darwin regarded as the raw
materials for the selective process are not generally hereditable.
The wisdom of retaining the term Natural Selection may therefore be
questioned. In all probability there is another reason which in part
explains the popularity of Darwin’s theory as contrasted with the
neglect of Mendel’s pioneer labours. Natural selection was suggested
by the analogy of industrial conditions in the nineteenth century.
Once formulated as a universal principle of nature it appealed to
the dominant political theories of the period. The Origin of Species
became the bible of _laissez faire_. It triumphed as classical humanism
triumphed during the Middle Ages in part at least for reasons which
were primarily political. The idea that the struggle for existence is a
constructive process played a prominent part in the social theories of
the Selectionist School.
A great deal of confusion can be dispelled if we recognize that Darwin
never clearly distinguished between two distinct issues. His herculean
labours in the field of geographical distribution urged him to seek a
reason for the circumstance that different species of animals exist in
different parts of the world. The struggle for existence does explain
why some species have died out in one place while others have died
out in other places. From that point Darwin went on to generalize
about the Origin of Species, i.e. how species come into being. It is
unfortunate that, though most of his earlier and enduring contributions
to science are concerned with how certain species have ceased to
exist, the title of his work laid emphasis on the process by which
species are brought into being. It was naturally this part of his
theory which made the greatest appeal to his contemporaries. Possibly
it was not the one which was most significant to Darwin himself.
Darwin used the term Natural Selection in connexion with both problems.
With regard to the former his theory is as acceptable as ever. With
regard to the latter it has now been superseded by exact experimental
enquiry into the mechanism involved in the production and preservation
of new hereditable types. The work of Gregor Mendel is the proper
starting-point of such enquiry.
A third aspect of the Principle of Genetic Variation concerns the
adequacy of geological time. It will only be touched on briefly. When
the evolutionary theory was introduced to the biological world, it
had to encounter a difficulty that no longer presents itself as a
formidable objection. Kelvin had calculated the possible period of time
during which life can have existed from considerations derived from the
rate of cooling of the earth. The allowance which Kelvin conceded was
subject to the qualification that no factors at that time undiscovered
enter into the question significantly. Since that time the discovery of
radio activity has removed the necessity to place any such restriction
on the period of geological time, as Kelvin was led to deduce. To-day
we have no reason for believing that geological time is too short to
permit us to ascribe the faunistic changes of successive generations to
the operations of the natural process of genetical variation. At the
same time the Evolution Theory will not stand side by side with the
retrospective hypotheses of astronomy in the hierarchy of scientific
generalizations, until the frequency of genetical variation and the
conditions which determine it have been correlated with more exact
knowledge of the duration and climatic features of the intervals
corresponding to geological strata.
§3
There remains another aspect of the Principle of Genetic Variation.
This is of paramount importance in connexion with the evolutionary
hypothesis. It is the Origin of Species _sensu stricto_. A good deal
of confusion has arisen in the discussion of the species problem on
account of the equivocal usage of the word _species_. It is therefore
best to begin with a clear definition of the species problem. It is a
universal experience that any dog resembles its father and mother in
more respects than it resembles any cat or any fish; any cat resembles
its father and mother in more respects than it resembles any dog or
any fish; any fish resembles its father and mother more closely than
it resembles any cat or any dog. We may express this by saying that
cats, dogs and fish have certain specific hereditable properties. If
we examine these hereditable properties we find that a cat has more
hereditable properties in common with any dog than those which it
shares with any fish. Thus organisms can be arranged or classified
in groups expressing the extent of resemblance in their hereditable
properties. The work of Ray and Linnæus in the early half of the
eighteenth century led to the general belief that “like begets like,”
and the publication of the _Systema Naturæ_ (1757) by the latter author
marks the beginning of a century and a half of detailed anatomical
studies directed to classification of this kind. According to the
degree of resemblance of organisms with respect to their hereditary
properties they are customarily grouped in phyla, classes, orders,
families, genera and species. To illustrate the meaning of these
terms let us consider the reader of this essay. He or she is said to
belong to the species _sapiens_ of the genus _Homo_, which includes
all living races of man. The genus _Homo_ includes in addition _H.
Neanderthalensis_, the early stone-age heavy-browed first men, and is
grouped with the genera _Pithecanthropus_ and _Eoanthropus_ (the fossil
ape man of Java and Pilt Down man) in a family _Hominidæ_, within the
order _Primates_, that comprises apes, monkeys and marmosets. The order
_Primates_ is one of many orders of forms within the class _Mammalia_
that includes hairy animals that suckle their young. The _Mammalia_,
along with birds, reptiles, amphibia (frogs, toads salamanders) and
fishes, is placed in the phylum _Vertebrata_, which includes all forms
with a backbone.
The degree of similarity implied by placing two species in the same
genus, order, class, etc., is an arbitrary one defined by convenience
and general consent. The degree of similarity implied in placing two
individuals in the same species in the sense in which the term was
defined by Linnæus implies something more than convenience. Linnæus
placed within the same species all individuals which breed readily with
one another. The structural difference between two Linnæan species
of animals and plants may be negligible compared with the immense
structural differences that distinguish varieties within a single
Linnæan species, as for instance the difference between White Leghorns,
Yokohamas, Silkies, Partridge Cochins, etc., which are all members of
the species _Gallus domesticus_.
Though this definition of the species as a unit is the one sanctioned
by priority, it is insufficiently emphasized by those who discuss
evolution that the creation of new species in the daily routine of a
large museum has very little to do with the Linnæan test. Preserved
animals are sent by collectors to the taxonomist, who proceeds
to classify them in new species, varieties or genera in the vast
majority of cases without any experimental knowledge as to their
breeding habits. Hence the terms species and variety are in practice
used to a large extent interchangeably, though not deliberately. The
historic problem of the origin of species is not that of the origin of
museum species but of Linnæan species. If we can show that discrete
hereditable properties arise, as we know that they do, discontinuously
in the normal course of generation, we have all the materials we
need to interpret the origin of varieties, genera, orders, families,
classes, phyla. Whereas all these are arbitrary groups defined in terms
of similarity and difference of the hereditable anatomical properties
of animals and plants, the species, as defined by Linnæus, is a group
limited not merely by the anatomical resemblance of its individual
members but also by _their inability to breed successfully with other
forms_.
What has been said so far about the origin of new hereditable
properties bears directly upon the way in which new varieties arise.
New varieties will only retain their characteristics if some external
agency is employed to prevent them from hybridizing and thereby giving
rise to an indefinite number of new combinations of characters. The
Yokohama can be made to retain those characteristic differences which
distinguish it from a White Leghorn by the mechanical device of
separating the two strains with a partition of wire netting. No wire
netting is required to prevent a White Leghorn and a turkey from losing
their genetic individualities, when they are placed in propinquity to
one another as are closely allied species in Nature. There is therefore
in addition to the problem of the origin of new varieties a problem
of the origin of species incompatibility. This cannot be dismissed as
of no importance, so long as our experimental knowledge of the origin
of varieties fails to suggest in what way this incompatibility may
arise. If we can solve this new problem the evolutionary hypothesis
presents no ulterior difficulties in the way of explaining the origin
of differences which separate the larger systematic groups. The
differences employed in distinguishing genera from varieties, and
orders from genera or classes from orders are differences of degree.
Between species, superficially at least, there seems to be a difference
in kind. On this account the origin of species has always been taken to
signify the core of the evolutionary problem.
In a somewhat panegyric vein Mr. H. G. Wells replying to Hilaire Belloc
makes the following remark: “Darwin’s book upon the subject was called
_The Origin of Species_. It was a very modest and sufficient title. He
did not even go to the length of calling it the origin of genera or
orders or classes.” Surely Darwin might much more appropriately have
employed the latter. How types which are structurally different arise
may or may not be accounted for by the selection hypothesis. How types
which will not breed with one another arise within the same stock is
not relevant to it. It is true that Darwin and Wallace vaguely referred
in their writings to a natural tendency to infertility as forms become
more sharply differentiated. This does not meet the difficulties of the
case, even if it is a sound experimental doctrine. Bateson has used
the following illustration to emphasize the irrelevance of Natural
Selection to the species problem in the strict sense of the term:
“Sometimes specific difference (anatomical differences between
species) is to be seen in a character which we can believe to
be important in the struggle, but at least as often it is some
little detail that we cannot but regard as trivial which suffices
to differentiate the two species. Even when the diagnostic point
is of such a nature that we can imagine it to make a serious
difference in the economy, we are absolutely at a loss to explain
why this feature should be necessary to species A, and unnecessary
to species B, its nearest ally. The house sparrow (_Passer
domesticus_) is in general structure very like the tree sparrow
(_P. Montanus_)... They differ in small point of colour... The two
species therefore, apart from any difference that we can suppose
to be related to respective habits, are characterized by small
fixed distinctions in colour-markings, by a striking difference in
secondary sexual characters and by a difference in variability. In
all these respects we can form no surmise as to any economic reason
why the one species should be differentiated in one way and the
other in another way, and I believe it is mere self-deception which
suggests the hope that with fuller knowledge reasons of this nature
would be discovered.”
It is permissible to argue that the final justification of the
evolutionary argument will be achieved when intersterile mutants have
been shown to appear under experimental conditions. We shall then
be able to state that new types which display not only anatomical
but specific discontinuity have arisen in the ordinary course of
generation. At present it is only possible to say that we have very
good reason to believe they can do so. Bateson overemphasized the
difficulty of the species problem when he said “the production of an
indubitably sterile hybrid from completely fertile parents, which
have arisen under critical observation from a common origin... is the
event for which we wait.” Although the origin of the species barrier
does introduce a novel issue into the discussion of the evolutionary
problem, its novelty is not so fundamental as it appears to be at first
sight. Morgan remarks with justice:
“The necessity of putting the mutation theory to the test that
Bateson calls for seems to me very doubtful, for while this is one
of the possible ways in which a mutant might split off at once from
the parent type, it is by no means the only way or even, I think,
the most probable way in which species have become separated....
There is no one problem of infertility of species and no one
problem of the sterility of hybrids, but many problems, each due to
differences that have arisen in the germinal material. One or more
of these differences may affect the mechanism of fertilization or
the process of development, producing some incompatibility.”
Bateson performed a most important task in emphasizing that the problem
of species discontinuity exists. He made its solution assume more
formidable proportions than the facts merit. There is no mysterious
wholeness about the concept of the species barrier. Like other
scientific concepts it defines a class of properties. When we examine
the characteristics of species barriers, we at once see that they
constitute a very heterogeneous assemblage of hereditable properties,
many of which are recognizably similar to hereditable properties which
we know to arise as mutants in genetic experiments. An individual may
be placed in a different species from another individual because of
some merely anatomical difference in the structures associated with the
copulative act. Owing to the respective absence of neck hackles and
tail feathers in two strains known as the Barbadoes and Rumpies, the
male of the latter cannot successfully tread the female of the former,
though each is interfertile with other breeds of domestic fowls. The
origin of such differences does not constitute a problem of a different
class from the origin of other varieties. High and low fertility are
hereditable properties that can be studied as varieties within the
species group. They have arisen as mutant characters in experiment.
If there arose within a stock mutants with complementary genes for
infertility either type would be infertile with respect to the other.
They would constitute separate species in the Linnæan sense, when the
parent stock died out. In the case of the donkey and the horse, we
can go further and identify the complementary sterility factors in
the structure of the chromosomes. Difference of size and shape in the
chromosomes of the donkey and horse prevent them from pairing in the
reduction division, so that no ripe sperm is formed in the testis of
the mule. Mutants differing with respect to chromosome numbers and
sizes arising by fragmentation or fusion are known both in plants and
animals to have arisen under experimental conditions. In many plants
they have been perpetuated by self-fertilization. Plough has raised a
mutant strain of Drosophila which is more fertile _inter se_ than with
the wild stock. The genetic basis of interspecific sterility, while
worthy of much more extensive research, is now reaching a precision
which places the experimental data of evolutionary theory beyond the
plane of Malthusian speculation.
The foregoing illustrations do not exhaust the variety of biological
characteristics which separate one individual from another as a member
of a different Linnæan species. Nor do they exhaust the types which can
be brought within the realm of experimental treatment. Other cases are
discussed at length in Crew’s _Animal Genetics_. The species barrier is
not one thing but many things. In the light of modern research there is
no reason to regard the origin of species barriers as an essentially
different problem from the origin of varieties. Nevertheless the two
issues are superficially distinct. No discussion of the present status
of the evolutionary hypothesis is complete unless the distinction is
submitted to critical examination in the light of experiment.
In the opening years of the twentieth century it had become the
fashion among biologists to treat evolution as a dogma. The growth of
experimental study of inheritance and variation tends rather to make us
value it as a hypothesis suggestive of further enquiry. The difference
between the two attitudes is akin to a difference of method which
mankind has adopted throughout the ages in the pursuit of knowledge.
One method rationalized in its most rigid form in the philosophy of
Hegel is to seek for some proposition to which every one is agreed and
proceed by deduction to whatever conclusions may be reached from the
starting-point. This method has proved invaluable to politicians and
members of the legal profession in the discharge of their vocational
activities. It is essentially like that of the schoolmen who would
exhaust themselves in untiring search into the writings of the ancients
for some authoritative statement regarding the number of teeth which
the horse possesses, a statement that no one would dare to question.
The scientific method is irreconcilably opposed to the Hegelian
method. With no aspirations to good breeding it prefers to look the
gift horse in the mouth. It is just those propositions which every
one accepts that the scientist is most anxious to examine in the hard
light of experience. In attempting to envisage a natural mechanism by
which the graded differentiation of animal structure could have been
brought about, Lamarck was content to employ the generally accepted
belief in the inheritance of acquired characters without bringing
it to experimental test. Darwin, fortified with newer knowledge of
the historical succession of animals and plants as recorded in the
rocks, sought to show that evolution was a necessary consequence of
competition and the “strong principle of inheritance.” Darwin did
not undertake the task of enquiring into the nature of the “strong
principle of inheritance.” It was to him like one of Euclid’s axioms.
Mendel alone at this time saw the necessity for an experimental study
of inheritance, and pointed the way to a non-dialectical treatment of
the problem.
VII. NATURAL SELECTION AND EXPERIMENTAL RESEARCH
“Heredity as something quite incomprehensible cannot be used as an
explanation, but only as a designation for the identification of a
problem. And the same holds good of adaptability.”--Nietzsche, _The
Will to Power_
§1
To large numbers of people evolution is Darwinism, just as to our
fathers geometry was Euclid. In one of his writings Morgan has remarked
that “it is not so important to find out whether Darwin’s ideas were
as clear as our own, as to make sure that our own ideas are clear.”
This is true; but an interest in the history of scientific thought
is a blameless pursuit for its own sake; and there are ulterior
reasons which justify an historical discussion of the criticisms which
experimental discovery has brought to bear on the Selection doctrine
in its original form. During the latter half of the nineteenth century
the evolutionary hypothesis became entangled with the idea of a moral
progress of mankind. On this account some philosophers, who are not
biologists themselves, fail to recognize the ethical neutrality of
biological enquiry. It is doubtful whether the promulgation of any
scientific hypothesis has ever had so profound and, at the same time,
so immediate an effect on the attitude of educated people towards
personal responsibility and social obligations. The fate of Darwinism
is as much the concern of the layman as of academic biologists.
Nor is it easy for those who are not biologists to gain definite
enlightenment concerning the extent of the change that has taken
place. With the rise of experimental method the discussion of evolution
has become more technical owing to the accumulation of new data and on
account of the introduction of a more intricate form of logic. It is
a quantitative branch of science. There was a time when the biologist
thought it worth his while to read and to reply to Samuel Butler.
To-day there are biologists who read--and like the present writer
enjoy--the works of Mr. Bernard Shaw. They do not feel it necessary to
defend their philosophy against the arguments advanced in the preface
to _Back to Methuselah_. Popular expositions of evolution are still
written. More often than not one suspects that they are rather too
popular to answer the questions which an intelligent reader who is not
a biologist is most anxious to hear discussed.
As an exact science biology is still very young. Evolution is in its
infancy. Only in our generation has it become the nucleus of a growing
body of experimental research. It may be that when the history of the
evolutionary hypothesis is written two centuries hence, Bateson’s
_Materials for the Study of Variation_ will assume a more prominent
place than _The Origin of Species_. It may be that the name of Thomas
Hunt Morgan will be mentioned in its pages more often than that of
Charles Darwin. We are too near the footlights to view the matter
in its correct historical perspective. It is at least permissible
to entertain such a possibility. Ancestor worship has no place in
the ritual of science. If any display of sentiment is appropriate in
scientific discussion, it might be said that the only fit way in which
to honour the memory of a Darwin and a Newton is to press forward in
exploring the fields which their labours have fertilized.
Without entering into technicalities I shall make the attempt in this
essay to contrast the use of the term Natural Selection in Morgan’s
writings with the Darwinian doctrine in its original form. My aim will
be neither to justify in the one case nor exculpate in the other, but
to discover whether a difference exists, wherein the difference lies,
and how the difference has arisen. In contrasting the views held by
two men of science it is of the utmost importance to lay emphasis on
the type of data which they have respectively studied most. Morgan is
an experimental geneticist. Darwin was pre-eminently a geographical
naturalist. Morgan’s most brilliant contributions to the advance of
science have been focused on the study of those conditions which
are significant to the origin and transmission of new hereditable
properties in animals. Before the publication of _The Origin of
Species_ Darwin’s scientific labours had concentrated more especially
on amassing a wealth of information about the way in which species are
distributed in different parts of the world. In his long itineraries,
it is not difficult to surmise what aspect of the species problem was
constantly uppermost in Darwin’s thought. I think it is necessary to
appreciate this bias in any attempt to understand the way in which the
Selection hypothesis developed. Though Darwin spoke of the Origin of
Species, he was interested primarily in why some species happen to be
found in one place and other species in different places. Darwin had
two distinct problems in view when he set out to write _The Origin of
Species_. In the course of writing it he sometimes lost sight of the
distinction between them. One was how different types of animals have
come to persist in different parts of the world. The other was how
an evolutionary process could take place at all. That the struggle
for existence is the key to the former is highly plausible. No facts
are known which contradict such a view. It is not really an issue
with which the modern experimentalist concerns himself. Up to this
point there is no divergence between the Darwinian and the Mendelian
standpoint. But Darwin in very unequivocal language committed himself
to the view that in building up new specific forms the struggle for
existence makes use of all differences between parent and offspring
of “whatsoever” origin. He thus implicitly encouraged the view that
natural selection is a creative agency. Herein lies a fundamental
difference between the standpoint adopted by Morgan and the Darwinian
doctrine. Darwin really believed in the Origin of Species by natural
selection. Morgan believes in the Origin of Gaps by natural selection.
It is perfectly true that Darwin did not formulate this deduction so
explicitly or so prominently as did some of his followers. But it was
logically implicit in his earlier writings and very definitely set
forth in his later. It was in virtue of this aspect of the Natural
Selection hypothesis that evolution captured the support of Darwin’s
contemporaries. Till Darwin’s book appeared, biologists did not for
the most part believe that evolution could take place. Darwin’s
hypothesis demonstrated that evolution must take place in a world in
which organisms had to struggle for their existence. The experimental
data which Morgan employs as the basis for his conception of the
evolutionary process imply that the reasons which led the pre-Darwinian
biologist to think that evolution could not take place are unfounded.
They also imply that the reasons which Darwin advanced to show that
evolution _must_ take place are wrong.
It is easier to make this distinction clear at a later stage with the
aid of a concrete example than by stating general propositions. This
is because one result of experimental progress has been a change in
our use of the concept of “variation.” Darwin used the term variation
for any difference between parent and offspring. In affirming that the
struggle for existence makes use of all variations for building up
species differences, he logically implied one of two things. Either
all differences between parents and offspring are genetic in origin,
that is to say, referable to differences in the egg or sperm; or
alternatively bodily modifications which occur during the lifetime of
an individual influence the genetic structure of the offspring so as
to produce an analogous result. This principle, usually associated
with the name of Lamarck, was accepted by every one in Darwin’s time.
Darwin himself, while ridiculing Lamarck’s idea of the _modus operandi_
of evolution, accepted the inheritance of acquired characters. There
was therefore no need for him to make a distinction between the
two alternatives. Neither the one nor the other is in harmony with
the standpoint of a modern geneticist of Morgan’s school; but the
difference between the Darwinian standpoint and that of Morgan concerns
not only the question of fact but the deductions drawn from it.
The difference between either of these alternatives on the one hand and
the Mendelian standpoint on the other can be illustrated by reference
to one of Mendel’s original experiments on the hybridization of peas.
In crossing pure-bred peas of the variety characterized by a dwarf
shoot with the normal tall variety, Mendel obtained only tall types
on the first generation, and in the second generation derived from
crossing the latter _inter se_ one-quarter were dwarf and the remaining
three-quarters tall. Now the individuals of either the tall or the
dwarf class are not all alike. Any dwarf shoot grown under ordinary
conditions is distinctly smaller than a tall shoot, so that the two
classes are discontinuous and quite easily distinguishable; but when
the conditions are standardized as much as possible small differences
of light, moisture, soil-content, temperature or proximity exert their
influence, so that no two dwarf plants are of exactly the same size.
What is transmitted through the gametes is something which determines
the extent to which an individual is capable of growing under
appropriate conditions. This distinction greatly clarifies our thought
about the so-called inheritance of acquired characters.
A criticism of the Lamarckian doctrine is irrelevant at this juncture.
It is referred to in this connexion because it was only in the
eighties, after the Lamarckian view was challenged by Weismann, that
the full force of the logical implications of Darwin’s teaching was
felt. It is true that his followers were far more definite than the
author of _The Origin of Species_ in emphasizing the creative rôle of
selection. It is true that the discredit into which the Lamarckian
principle fell after the discovery of the nature of fertilization
led the Selectionist writers to exaggerate this aspect of Darwin’s
hypothesis. Nevertheless Darwin did express himself in unmistakable
language with regard to this issue. His followers, forced to be more
specific concerning the nature of differences between parents and
offspring, made the bold, and, it transpired, unwarranted assumption
that all those small differences between parent and offspring now
referred to as fluctuating variability are in the main genetic in
origin. The Selectionist doctrine thus assumed that hard outline which
produced its first vigorous reaction in Bateson’s _Materials for the
Study of Variation_ (1894), a work which laid down the main lines of
investigation which have been elucidated by the Mendelian renaissance.
To avoid vagueness concerning what Darwin actually did say I shall
quote once more from _The Origin of Species_:
“Any being, if it vary in any manner profitable to itself, under
the complex and sometimes varying conditions of life, will have a
better chance of surviving, and thus be naturally selected. From
the strong principle of inheritance, any selected variety will tend
to propagate its new and modified form.” (Introduction.)
“Each of the endless variations which we see in the plumage of
fowls must have had some efficient cause; and if the same cause
were to act uniformly during a long series of generations on many
individuals, all probably would be modified in the same manner.”
(Chap. 1.)
“A high degree of variability is obviously favourable as giving
the materials for selection to work upon, not that mere individual
differences are not amply sufficient, with extreme care, to allow
of the accumulation of a large amount of modification in almost any
desired direction.” (Chap. 1.)
“Over all these _causes_ of change, the accumulative action
of selection, whether applied methodically and quickly, or
unconsciously and slowly but more efficiently, seems to have been
the predominant power.” (Chap. 1.)
“Variations, _however slight, and from whatever cause_ proceeding,
if they be in any degree profitable to the individuals of a
species, in their infinitely complex relations to the individuals
of a species... will tend to the preservation of such individuals
and will generally be inherited by the offspring. The offspring
also will have a better chance of surviving, for of the many
individuals of a species which are periodically born, but a small
number can survive. _I have called this principle, by which each
slight variation if useful is preserved, by the term Natural
Selection._” (Chap. 3.) (Italics inserted.)
If, as Darwin believed, it were true, that variation occurs in every
generation, the evolutionary process would be a continuous one. To
Morgan the production of mutants is a discontinuous break in a
normal routine of stability. To Darwin variation and heredity were
co-extensive terms. The offspring are always on the whole like their
parents. That resemblance constitutes inheritance. On the other hand
they are never quite the same. The difference was what Darwin called
variation. To Morgan heredity and variation are not co-extensive terms.
The structure of the chromosomes is fundamentally stable. From time
to time there occur disturbances of this normally stable equilibrium.
New hereditable properties emerge into being in a quite discontinuous
fashion. There is no self-evident reason why a particular stock should
not remain indefinitely in a phase of stability. To the experimental
geneticist there thus exists no difficulty in interpreting the fact
that some animals have remained unchanged since the earliest rocks.
To the generation in which Darwin lived there seemed to be only one
logical outcome of the view that variation is a continuous process
involving all the individuals of every generation. This deduction
was never stated very explicitly by Darwin himself, though it was
definitely asserted by Wallace. There can be no doubt that this
deduction gave the Selection hypothesis such a strong appeal to
Darwin’s contemporaries, and contributed largely to the success of
the hypothesis of Natural Selection. Before Mendel, investigators
in hybridization had treated the individual as the unit for study.
From this arose the belief that hybrids are intermediate between the
parents. This belief in its turn gave rise to the notion that on
crossing a new type back to the parent stock there would be a dilution
of the new character, culminating after a number of generations in
swamping it out of existence altogether. Evolutionists of the Darwinian
period therefore introduced a variety of devices, such as geographical
isolation and, above all, the survival of the fittest, to counteract
the effect of this swamping and account for the persistence of new
types. To Darwin’s generation it seemed that without selection there
could be no evolution. The new type would always be swamped out in the
long run. In the struggle for existence the less viable variations
would tend to be eliminated, and since there would always be less of
them on that account, the swamping process would favour the gradual
moulding of the species in the direction of more favourable variation.
On this view the struggle for existence is the agency which makes
species change. Evolution becomes a necessity.
From Morgan’s standpoint evolution is only a necessity in so far as
it happens that mutants do from time to time appear. The struggle for
existence though eliminating the less viable types has no creative
rôle in the Darwinian sense. Mendelian analysis shows that though
the first generation of a cross between pure-bred parents may be
intermediate between the parental types, both parental types appear
in their original purity in the next generation, and will continue
to breed true to type, whenever they mate with other individuals
similarly constituted. The modern geneticist feels no necessity for
an _argumentum ad hominem_ to explain how evolution can occur in
spite of a supposed swamping process. To him the swamping process is
an illusion based on imperfect knowledge of the facts of hereditary
transmission. The importance of this difference in standpoint lies in
the fact that the idea of natural selection would never have assumed so
powerful an influence over biological thought, unless it had provided
the evolutionist with train of reasoning which seemed to prove that
evolution must be going on all the time.
This interpretation of the Darwinian standpoint is not a caricature
drawn by the pen of an adverse critic. An enthusiastic contemporary
exponent of Natural Selection, Mr. H. G. Wells, thus defines the
selection theory in his _Outline of History_:
“the young which a living thing produces... are like the parent
living thing. But they are _never exactly like it_ or like each
other.... Suppose, for example, there is some little furry
whitey-brown animal living in a bitterly cold land which is usually
under snow. Such individuals as have the thickest, whitest fur will
be least hurt by the cold, less seen by their enemies and less
conspicuous as they seek their prey. The fur of this species will
thicken and its whiteness increase _with every generation_, until
there is no advantage in carrying any more fur.” (Italics inserted.)
Having cited the above, it is somewhat surprising to note that in
replying to Mr. Belloc’s strictures, Mr. Wells makes the following
statement with reference to the Natural Selection theory:
“Among questions bearing upon it but not directly attacking it
has been the discussion of the individual difference.... What
rôle is played by what one might call normal relatively slight
differences and what by the sports. Can differences establish
themselves while outer necessity remains natural? Can variations
amounting to specific differences... be tolerated rather than
selected by Nature?... What happens to differences in cases of
hybridization?... None of these subsidiary questions affect the
stability of this main generalization of biology.”
In explaining the Natural Selection theory, as quoted above, Mr. Wells
himself states or implies every one of these “subsidiary” questions,
and answers them in his own way.
Let us now see how a modern geneticist would interpret the evolutionary
process by taking an analogous concrete example. He would argue
somewhat as follows. Supposing a single white mutant hare arises in a
grey parent stock, the behaviour of the chromosomes leads us to infer
that eventually other white hares, pure for the white gene or genes,
will reappear. These mated _inter se_ will breed true to type. On the
assumption (not conclusively proved) that it is advantageous for a hare
in temperate climates to be grey and in arctic regions to be white,
there will be more white hares in the long run in northern countries
and more grey ones in temperate countries. If there were no competitive
struggle at all, there would in the long run be grey and white hares in
northern and grey and white hares in temperate countries. There would
have been the same amount of evolution. The only difference that the
struggle for existence introduces is that the final picture presents
a more discontinuous aspect. This was not at all what Darwin meant by
Natural Selection. He would have said that a single mutant would be
swamped out of existence by intercrossing. He would have formulated the
problem in the following terms. Of all hares born to grey parents some
are lighter and others darker. In a region where it is advantageous,
the half that are lighter than the mean will have more chance of
surviving to maturity. In any given generation there will therefore be
more lighter than darker parents. The result of this will be that in
every generation the swamping process will always be on the side of
the lighter individuals. Darwin postulated that, if this process went
on long enough, a white hare would eventually be produced. Such a race
would only be produced in the region where natural selection favoured
its survival. On this view natural selection is the creative agency,
or at least a paramount creative agency in the evolutionary process.
Without the struggle for existence hares everywhere would remain grey.
In every generation the half that are lighter than their parents would
always be swamped by the half that are darker.
To Darwin and more especially to Darwin’s followers selection was the
agency which preserved not merely new individuals but new characters,
since characters would otherwise be diluted out of existence. For
Morgan the preservation of new characters ultimately resides in
Mendel’s law of segregation. It has its material basis in the behaviour
of the chromosomes. The contrast between the alternatives is at once
made clear when we consider what would happen in a universe so large
and so abundantly supplied with the necessities of life that no
struggle for existence intervenes. Given unlimited time in a Mendelian
universe in which natural selection did not operate, all the species
we know to-day would be present, and many more besides. Evolution
would have occurred; but the pageant of life would present to the
taxonomist a more continuous appearance, and the striking gaps which
we now see would be filled not by fossil relics but by living forms.
Except in so far as he was prepared to invoke the Lamarckian principle
to circumvent difficulties inherent in his own hypothesis, natural
selection was to Darwin the necessary condition not merely for gaps but
for any evolution to take place at all. In a Darwinian universe without
natural selection there would be no progressive differentiation of new
characters.
§2
When, out of deference to Darwin’s contribution to biological thought,
the experimentalist of Morgan’s school asserts his belief in Natural
Selection, he is in fact referring to something very different from
Darwin’s Natural Selection, indeed to a view of the process which
Darwin would have rejected emphatically. Of course it is admitted that
all scientific hypotheses become modified as new data accumulate; and
phrases imperceptibly change their meaning in the course of time.
But the natural selection of Morgan’s school is not a continuous
development from the original concept. Within two decades of the
publication of _The Origin of Species_ the selection hypothesis had
assumed a clarity of outline which had an influence on subsequent
developments in biological thought, persisting till the present day,
and not likely to disappear for some time. In 1881 Weismann challenged
the prevailing belief in the inheritance of acquired characters.
Thenceforth in the hands of the Selectionists environment became merely
an agency by which the hereditary materials are preserved or rejected.
As an aspect of the problem of development it faded into the background
of the picture. To question the almightiness of heredity became
equivalent to defending the Lamarckian principle, though the two issues
are logically independent.
Educated people frequently use the words environment and heredity in
a very different sense from that in which they are employed by the
biologist. Unless we are accustomed to the study of embryonic and
larval life, we are apt to think of an organism as a finished product.
The rôle of environment and of heredity as seen through the eyes of
a contemporary biologist can be made explicit by reference to recent
work on the metamorphosis of tadpoles. We know to-day that the thyroid
gland of all vertebrates contains a high percentage of iodine. Barger
and Harrington have now prepared in pure crystalline form an iodine
compound which has the same therapeutic properties as extracts of
the thyroid gland. A few years ago the discovery that frog tadpoles
will change very rapidly into adults if fed with thyroid gland, was
followed up by the development of a successful technique for removing
the rudiment of the thyroid gland in frog embryos. Thyroidless tadpoles
never undergo metamorphosis. They continue to grow as tadpoles when
the normal tadpole would change into a frog. The change into the adult
in the normal tadpole is initiated by the liberation of the thyroid
secretion into the circulation. It has also been shown that tadpoles
reared on an iodine-free diet in water containing no trace of iodine
remain permanently in the larval state. This clarifies what is meant by
an _environmental_ factor in development. In contradistinction to the
influence of environment the influence of inheritance in development
may be illustrated by reference to an American salamander, _Amblystoma
tigrinum_, which has a characteristic larval form. In the lakes around
Mexico city there is a local race of this species which never undergoes
metamorphosis in nature, reproducing in the larval form. It can be
made to develop into the land-dwelling adult in a few weeks, if fed
with thyroid gland in the laboratory. Addition of iodine salts to the
water in which it lives or to its food will not induce metamorphosis.
Its permanent fixation in the larval stage is due to the fact that it
_inherits_ from one generation to another a deficient thyroid gland,
which cannot make use of the iodine in its surroundings. Absence of
iodine in minute quantities from the water, a purely environmental
agency, or on the other hand a hereditary difference between two races
with respect to the efficiency of thyroid secretion, may either of
them be _independently_ instrumental in deciding whether a particular
individual shall attain sexual maturity in the form of an air-breathing
land-dwelling salamander, or an aquatic half-way house between a
salamander and a fish. A geological epoch, if you like to put it in
that way, is thus summed up in a mutant gene or in a trace of iodine.
In the attempt to understand the tenacity with which belief in the
Lamarckian view persisted in biological thought, it must be borne
in mind that embryology is the most recently developed branch of
anatomical science. Until the classical researches of von Baer and
Meckel were published in the first half of the nineteenth century, the
prevailing idea about development was the teleological doctrine that
an animal is from the very first complete in all its parts and only
needs growth to make its minute structure manifest to the eye. Caspar
Wolff in 1759 made observations on the hen’s egg, and was led to state
the “epigenetic” as opposed to the prevailing “evolutionary” view. He
sought to show that the hen’s egg is at the beginning without any gross
anatomical organization and that structural organization within the
egg is a gradual development. His work failed to attract attention.
Von Baer’s researches on the same subject were published synchronously
with the formulation of the Cell doctrine (1832). One might say that
until the middle of the nineteenth century, the current conception of
inheritance in biology was closely analogous to the legal notion. The
parent was supposed to hand on its anatomy to its offspring in the same
sense as the well-to-do hand on their belongings. With so erroneous
a conception of the nature of development prevailing, it is little
wonder that the idea of the inheritance of acquired characters seemed
a perfectly reasonable one. It is not surprising that the doctrine of
Lamarck should have been first challenged during the decade in which
the nature of fertilization and the process of maturation of the germ
cells were elucidated.
As stated by its author the Lamarckian principle implied that any
reaction of the organism to its environment is carried over to
subsequent generations. It was especially _adaptive_ reactions such
as the effect of use and disuse which Lamarck emphasized in his
evolutionary speculations. When the Lamarckian principle was first
challenged, prominent scientists like Cope were willing to assert such
fables as the story that a cock deprived of one eye transmitted eye
defects to all his offspring. When it was conclusively proved that
mutilations effected through several generations left no impress on
the hereditable characters of the stock, the Lamarckians fell back
on the gratuitous postulate that only “adaptive” changes could be
transmitted. The precise meaning of this adjective was never defined,
nor was any reason forthcoming to suggest the existence of a mechanism
that could discriminate between mutilations and bodily changes that are
“adaptive.” This is yet another example of the perils of introducing
teleological preoccupations into the construction of biological
hypotheses. If recent experimental research conserves any element
of truth in the Lamarckian idea, it has robbed it of any special
significance to the way in which adaptive structures originate.
Structural changes may arise in the course of development from two
conceivable sources. The chromosomes which represent the hereditary
materials may find themselves reacting to a different type of “internal
environment.” The majority of modifications in the normal course of
development undoubtedly come within this category. Modifications of
this type, including in all probability relative sizes of organs, all
mutilations and habits are clearly not hereditable. Belief in their
hereditability was only possible so long as biology was dominated
by teleology and the essential features of the reproductive cycle
were undiscovered. There is another possibility which was entirely
disregarded by Weismann in his Theory of the Germ Plasm. It is a
possibility that has no bearing on the problem of adaptation. If
environmental agencies can produce mutations by a structural change
in the chromosome itself, there is no reason why such structural
changes should be confined to the chromosomes of the germ cells. We
must therefore preserve an open mind with regard to the possibility
of encountering phenomena having a superficial similarity to what
is implied in Lamarck’s doctrine. The exposure of young larvæ of
the fruit-fly to X-rays has led to the production of individuals
which show bodily resemblances to forms which have arisen in the
ordinary course of events as mutants. The effect of X-rays may be
to change the environment in which the chromosomes operate. But
the recent investigations of Patterson indicate the likelihood
that the modification is due to the action of the X-rays on the
chromosome itself. We know that X-rays will produce mutant changes
in the chromosomes of the germ cells. If Patterson’s interpretation
is correct, it may well be found that X-rays can simultaneously
effect mutant changes in all the chromosomes of the body. If applied
sufficiently early in the course of development, radiation with
X-rays would then produce bodily changes of a transmissible nature.
This possibility resides in the fact that the agent is capable of
acting on all the cells of the body in the same way at the same time.
There is no inherent unlikelihood that temperature and the chemical
constituents of an animal’s food may simultaneously produce bodily
and germinal mutations. Strictly speaking this is not the same as the
traditional belief in the “inheritance of acquired characters.” The
Lamarckian principle completely disregards the distinction between
modifications which arise from a change in the internal environment of
the chromosomes and a physical change in the chromosomes themselves. It
takes no account of the possibility that the environmental agent can
act in the same way simultaneously on all the cells of the body.
There are still students of fossil forms who claim that the
traditional Lamarckian view is necessary to explain the historic
succession of animals by continuous generation. There seems to be no
satisfactory reason to justify the statement that evolution can only
be satisfactorily explained by assuming the inheritance of acquired
characters. If there were, it would not be an argument in favour of
the Lamarckian principle. It would be as an argument against the
evolution theory. It would imply that the truth of evolution depends on
assuming a mechanism whose existence is most unlikely. What is often
called the neo-Lamarckian standpoint, the view that acquired characters
only gradually become impressed on the hereditary constitution after
countless generations, transfers the issue from the plane of verifiable
experience to one of pure surmise, rendering further discussion
profitless. In such a matter as this when experiment is silent, the
student of fossils must also be silent.
The objection rests in fact on a misapprehension. The earlier phase of
experimental enquiry along the lines laid down by Mendel was confined
to the analysis of simple clear-cut hereditary differences which
present themselves in almost any environment in which the animal can
live. They were also largely concerned with differences that could be
resolved into the simplest arithmetical ratios, or as Morgan would say
with mutants that have arisen through a change at a single point on
one pair of chromosomes. It is only as technique has progressed that
it has been possible to analyse the more complex cases in which single
characteristics depend on numerous Mendelian factors, or where the
character differences are so variable that they can only be defined in
statistical terms. The palæontologist being occupied very largely with
size differences is sometimes disappointed, because such phenomena lie
outside the scope of the simpler problems, which were once thought to
define the scope of the Mendelian hypothesis. Recent progress which has
led to the recognition that Mendel’s principle of segregation underlies
the inheritance of size is therefore of no little significance to
evolutionary theory. As we come to recognize the dependence of
hereditary transmission on discrete particles which maintain their
entities uncontaminated through all the cell divisions of the body,
segregating in their entirety in the formation of the gametes, the
unlikelihood of the Lamarckian principle in its traditional form
becomes more and more evident.
If the Lamarckian principle in its traditional form was undoubtedly
based on a confusion of ideas and an ignorance of fact, the Theory
of the Germ Plasm put forward by Weismann shows how facts may be
distorted to fit in with preconceived ideas which are in themselves
logically flawless. The discredit into which the Lamarckian principle
fell, almost as soon as the elementary facts about the nature of
fertilization became known, led Darwin’s successors to assume that
all those differences between parent and offspring which Darwin had
referred to under the term variations are genetic in origin. The
assumption was gratuitous, as later experimental analysis has shown.
Without that assumption the Selection doctrine would have been
robbed of the immense importance it had already begun to assume. From
a complete misapprehension of the true rôle of the environment in
relation to inheritance, the biological pendulum swung in the opposite
direction to a complete disregard of the influence of the environment
in relation to development. It is from Weismann’s writings that we
can best appreciate the fundamental dissimilarity of Darwin’s Natural
Selection and Morgan’s views. For Weismann’s “germinal selection” is
the logical outcome of Darwin’s selectionism, once it had been purged
of the Lamarckian principle. It is a triumph of Hegelian reasoning
applied to biology. There is nothing wrong with it but its premises.
Weismann’s theory embodied an atomistic conception of heredity.
Unlike Mendel’s it had no connexion with experimental data. Weismann
identified his hereditary determinants with the substance of the
chromosomes. Unlike Morgan’s hypothesis, Weismann’s speculations were
based on incorrect observations about the way in which the chromosomes
behave. In the long run the influence of Weismann’s teaching has
probably been more sterilizing than the Lamarckian doctrine which he
challenged.
Weismann imagined that his atoms of heredity or “determinants” multiply
in the cell and in some rather abstract way compete with one another
for survival. Hence the hereditary constitution of the individual
is never quite the same in two successive generations. Heredity
and variation are thus co-extensive, as Darwin’s Natural Selection
postulates. Weismann also thought wrongly, it transpired, that the
reduction division of the germ cells takes place in such a way that
each cell receives half a maternal and half a paternal chromosome
of each pair and not, as we now know, a whole paternal or a whole
maternal element. Hence he argued that the formation of the germ cells
involves not, as Mendel proved by experiment, a segregation but a
closer intermingling of the germinal materials. From this the swamping
of new characters on crossing became an absolute necessity. To Weismann
selection alone could prevent this swamping. Selection must act in
every generation, because the mingling of the hereditary materials
becomes more intimate with every generation. Only under the influence
of continuous selection could any change be brought about. Without it
universal stagnation would exist. In short Selection was the creator
and the preserver of the benefits of variation. In all this Weismann,
with the support of Wallace, went much further than Darwin himself.
But the Selectionist doctrine in its main features was implicit in
the Origin of Species. The sociological exploits of biologists belong
especially to the period in which the Selection doctrine assumed this
doctrinaire aspect. Doctrinaire Selectionism has persisted in our own
generation in the writings of many eugenists.
§3
We set out in the first place to contrast the views of the modern
geneticist with the Selection hypothesis in its original form. The
main differences arise in connexion with two issues. One concerns
Darwin’s own view that evolution is a continuous process. Darwin
believed that selection operates on all the individuals of every
generation. This implies either that acquired characters are inherited
or alternatively that all differences between parent and offspring are
hereditary differences in the modern sense. The views to which modern
geneticists have been led by their experiments are diametrically
opposed to both conclusions. The other question concerns the creative
rôle of selection. This belief arose from ideas about hybridization
and artificial selection current among those biologists to whom Darwin
addressed his argument. Darwin himself did not stress the point; but
it was this corollary of his theory which accounts for the successful
appeal which Natural Selection made to Darwin’s contemporaries. They
were satisfied that, if a struggle for existence occurs, evolution must
be taking place. This was because all biologists before Mendel confused
the characters which do blend with the genes that do not. To the modern
geneticist this corollary has no significance, because experiment has
forced him to reject views about hybridization prevalent before the
publication of Mendel’s researches. To Morgan, as to Darwin, selection
through the survival of the fitter is essentially like artificial
selection. Morgan differs radically from Darwin in his understanding
of the way in which artificial selection itself operates. According
to Morgan selection has no creative significance. “Selection has not
produced anything new, but only more of certain kinds of individuals;
Evolution however means producing new things, not more of what already
exists.”
Thus from the standpoint of Morgan the status of evolution is more
satisfactory in the light of modern research. For there is no need to
advance any special device to explain why new types are not swamped
out of existence through the blending of characters on crossing. From
the point of view of the Darwinians, if they were still with us, the
outlook would be disconcerting. The modern geneticist no longer regards
evolution as an imperative consequence of the struggle for existence.
On the other hand the modern view presents no greater difficulty than
the former one in explaining the tendency towards greater adaptation.
It is free from the objection that it proves too much. New hereditary
types would persist even if there were no struggle for existence. Since
there is one, the chance that a given mutant will reach the age at
which it can produce offspring will be greater if the mutant character
has “survival value.” At present there are insufficient experimental
data to make profitable the discussion of the amount of advantage
necessary to ensure survival. At the same time it is of interest to
record that the application of Mendelian method furnishes materials
for a precise statement of what selection can achieve and the rate at
which it works, when the extent of differential fertility or mortality
in a population is known. The mathematical theory of selection has been
made the subject of some illuminating researches by J. B. S. Haldane
and by Fisher. Haldane’s calculations have led him to conclusions very
different from the dialectical deductions which some eugenists have
drawn from the recent decline of the European birth rate.[7]
VIII. THE SURVIVAL OF THE EUGENIST
“I am that ancient hunter of the plains,
That raked the shaggy flitches of the bison:
Pass, world: I am the dreamer that remains,
The Man, clear-cut against the last horizon.”
Roy Campbell, _Flaming Terrapin_
Concerning Vesalius one of his biographers has said: “in dissecting
monkeys he became convinced that the many discrepancies between the
Galenic teaching and his own observations on the human body were due
to the circumstance that Galen had derived most of his knowledge from
dissecting monkeys, and had not thought it necessary to mention the
fact.” Perhaps the biographer of a future Vesalius who succeeds in
laying the foundations of social anatomy will record that “in studying
the writings of the Eugenists he became strengthened in the conclusion
that they were discussing the habits of fruit flies rather than human
beings, but had not thought it necessary to mention the fact.”
I have called this essay _The Survival of the Eugenist_; but I wish
to make it clear that I entertain no lack of sympathy for _Eugenics_
as defined in general terms by Galton, the Galen of social biology. I
have chosen this title to lay emphasis on the part which eugenists have
played in perpetuating a certain attitude towards human society. This
attitude starts from an examination of those characteristics which man
shares with all other animals, but neglects the equally important task
of defining those characteristics which distinguish man from all other
animals. The weakness of all mechanistic systems hitherto proposed
lies in their refusal to recognize the existence of anything which does
not yet come within the province of scientific method. A mechanistic
philosopher can legitimately entertain the hope that the study of
human society will become an ethically neutral science, and that the
methods of biology will fertilize sociological enquiry, as the methods
of physics and chemistry have fertilized biological investigation. He
is not entitled to pretend that biology can at present provide a key
to the interpretation of human history. I am well aware that there are
eugenists who would repudiate any such pretensions. At the same time
the general tendency of eugenic propaganda has been to exaggerate, and
grossly exaggerate, the applicability of genetic principles to the
analysis of human society. This tendency is a legacy of the period in
which Eugenic ideas had their origin.
Whatever disadvantages the Christian cosmogony imposed upon the study
of human society, it possessed the merit of emphasizing that the proper
study of mankind is man. The immediate influence of the evolutionary
controversy was a reversion to the Galenic practice in social anatomy.
There is nothing surprising in this reaction. To Huxley and Spencer the
important fact was that Man is a brute. It was necessary for them to
emphasize man’s genetic similarity to other animals in opposition to
the traditional view which placed man in a special category apart from
other natural objects. How strongly the need to emphasize Man’s new
status was felt can be inferred by a well-known dictum in _Man’s Place
in Nature_. “Whatever systems of organs be studied,” wrote Huxley, “the
comparison of their modification in the ape series leads to one and the
same result--that the structural differences which separate man from
the gorilla and the chimpanzee are not so great as those which separate
the gorilla from the lower apes.” In his dispute with Owen, Huxley went
much further than any modern anatomist would be prepared to follow him.
If like Cuvier he had based his objections on the structure of the
human foot instead of the hippocampus major, Owen might have made a
stronger case. His opponents were too busy disposing of man’s Cartesian
spirit to devote much attention to his Cuvierian sole.
The evolution of Thomas Henry Huxley, of Herbert Spencer and of Francis
Galton was a precocious baby. Its parents and relatives entertained
high hopes of its future career. In that tradition it has been nursed
by their loyal disciples who have encouraged it to discourse upon
sociology before it has learned to read and write. Huxley, Spencer and
Galton were fundamentally right in recognizing that any theory of the
development of human society implies certain biological assumptions.
Their anticipations of immediate progress in the biological treatment
of human society was inevitably coloured by the issues which made the
first claim on their attention. Those issues are no longer topical.
The experimental biologist of to-day cannot approach the structure of
human society from quite the same angle. The pioneers of evolution
were goaded by theological opposition to adopt an attitude which is
easy to condone but unnecessary to emulate. To justify their right
to speculate, they found it necessary to convince the non-scientific
public that their speculations were correct. To do so they were driven
to minimize the gap between man and the apes and make the best of
any evidence pointing to the missing link which popular imagination
demanded.
The missing link provided the occasion for one of the first
sociological exploits of anatomical science. There is an account of the
incident given in Dr. Haddon’s _History of Anthropology_. Three years
after _The Origin of Species_ was published Dr. James Hunt, President
of the Anthropological Society, read his paper on “The Negro’s Place in
Nature.” In it he maintained that “the analogies are far more numerous
between the ape and the negro than between the ape and the European.”
In 1866 he recorded a further contribution to the detection of the
missing link by asserting that “there is as good reason for classifying
the negro as a distinct species from the European as there is for
making the ass a distinct species from the zebra.” In this discussion
Huxley gave the exponents of the missing link a half-hearted support
tempered somewhat by his humane and sceptical disposition. An obituary
notice of Dr. Hunt in a New York paper announced in 1870 the “Death of
the Best Man in England.” Sixty years after the publication of Hunt’s
first communication, a leading American anthropologist, Professor
Kroeber, summed up the present state of knowledge in the following
terms:
“The only way in which a decision could be arrived at along this
line of consideration would be to count all features to see whether
the Negro or the Caucasian was the most unape-like in the plurality
of cases. It is possible that in such a reckoning the Caucasian
would emerge with a lead. But it is even more clear that which ever
way the majority fell, it would be a well-divided count.”
Speculation upon the ancestry of man has continued with unabated
vigour to the present time. Huxley’s generation had one good excuse
for confusing the process of social and organic evolution. It cannot
be pleaded by our own. Modern men were known to be associated with
the later palæolithic cultures. The Mousterian artefacts had been
associated with the Neanderthal type. There was much to encourage
the hope that further research would reveal a close parallelism
between the physical differentiation of specific or racial types
and successive stages of cultural development. It now appears that
Mousterian artefacts were also fashioned by types who, as Sir Arthur
Keith puts it, “would excite no comment, if dressed in modern
garb in any assemblage of modern Europeans.” Our own species has
served a long apprenticeship in a much earlier phase of cultural
development than that which was at one time attributed specifically
to the Neanderthalers. The data presented in Sir Arthur Keith’s
book _The Antiquity of Man_ show that it is not easy to press blood
relationships out of stone implements. There are already signs of a
reaction against the extravagant claims which have been put forward
by some physical anthropologists. The most recent hypothesis of the
origin of civilization completely breaks with the earlier tradition to
harp on the racial aspect of the problem. Professor Elliott Smith is
distinguished both as a physical and cultural anthropologist, and it is
therefore noteworthy that his theory emphasizes the characteristics of
man’s physical environment as the significant factors in the appearance
of the first civilized communities of the Nilotic region.
Under Weismann’s influence environment as an aspect of the problem of
development assumed a nebulous outline. For a generation biologists
were hypnotized by the discredit of the Lamarckian teaching. Eventually
the progress of experimental embryology and cell anatomy relegated
Weismann’s theory of germinal selection to the same limbo as the
Lamarckian hypothesis. In Weismann’s hands the Selection doctrine
had assumed a particularly rigid form. Evolution was necessarily a
continuous process. All differences between parents and offspring were
genetic. Heredity and variation were coextensive processes. From this
it followed that a continuous evolutionary process had accompanied
the development of social institutions. It was a natural step to
confuse the two. The conviction that eugenic legislation is a matter
of overwhelming urgency arose as a direct outcome of that step. That
the same confusion still dominates eugenic propaganda is illustrated
by a statement made by Mr. Lidbetter, a prominent eugenist, in his
paper at the World Population Congress of 1927, “It is a platitude,”
Mr. Lidbetter stated, “in these days to speak of natural selection as
the essential agent in human progress.” It may be a platitude. It is
not a truism. It is simply a misuse of terms. Social development is
the communication of social tradition and social accomplishment from
one generation to another, with the addition of new ingredients in
each. Organic evolution is brought about by the transmission through
the gametes of new hereditable properties. The mechanism of one is
education. The mechanism of the other is sexual reproduction. It is
possible that they react upon one another, but the extent to which they
do so cannot be ascertained by _a priori_ reasoning. The experimental
study of genetic variation has made it abundantly clear that evolution
is not a continuous process. At present we do not know the precise
conditions relevant to the production of mutant types; consequently
it is unjustifiable to make any general assumptions about genetic
variation in human societies without recourse to direct experimental
inquiry.
That is the task which now lies before the social biologist. Its
successful accomplishment will not be facilitated by under-estimating
the difficulties inherent in the problem. The study of human
inheritance is beset by innumerable obstacles. Man is a slow-breeding
animal of low fertility. His chromosomes are numerous. The geneticist
cannot control his matings. In spite of these drawbacks some insight
into the nature of hereditary transmission within the human species
can be gained by formulating the results of random mating on certain
hypothetical assumptions. Familial studies of colour blindness,
brachydactyly and the blood groups provide clear illustrations of
Mendelian phenomena. So long as family pedigrees are employed to
demonstrate the inheritance of physical characteristics, it is not
difficult to recognize the nature of the environmental influences
with which the hereditary materials react, and to make allowance for
them. The geneticist is on familiar ground. The constituents of man’s
physical environment have been classified by the physicist, the chemist
and the bacteriologist. Their effects upon the physical characteristics
of an organism form the subject matter of physiology. It is possible to
speak of the action of sunlight and humidity, oxygen pressure and diet,
infectious and contagious germs, iodine and calcium salts with some
measure of confidence. All these things are features of man’s physical
environment or of the physical environment of any other animal. The
methods for investigating their influence are well tried. The concept
of a uniform physical environment is tangible. It can be explained to a
pragmatist or a presbyterian, a behaviourist or a bimetallist.
It is another thing to speak about a uniform social environment.
The factors which determine man’s social behaviour are obscure and
elusive. Even to-day any dogmatism on the relative importance of
heredity and environment assumes an almost frivolous aspect when the
attitude of the experimental biologist is brought to bear on the
evidence. Analogies from the animal kingdom have been pressed into
the service of those who emphasize the rôle of either the one or
the other. Kropotkin’s _Mutual Aid_ was the _reductio ad absurdum_
of that attitude to social problems. Kropotkin was neither more nor
less scientific than the exponents of nature red in tooth and claw.
Both were irrelevant. The same irrelevance has been evident whenever
biologists have attempted to rationalize their political sentiments.
The anti-feminist appeals to the fighting and protective male. The
feminist can retort by invoking the worm Bonellia of which the male
lives as a parasite in the generative passages of the female. The
eugenist pictures the human poultry farm nicely mapped out in pens,
each surrounded by its own partition of wire-netting with a few holes
here and there. Maybe the Rhode Island Reds have scratched their way
into the proper preserve of the Partridge Cochins. Sooner or later the
cosmic poultryman, aided by wise statesmen, will put them back where
they belong. His opponents can reply that class differences exist in
insect communities. The difference between a white ant queen and a
termite worker is more striking than the difference between royalty and
factory girls; and it is a difference determined by diet. Encouraging
illustrations in support of any social doctrine can be brought forward
by those who prefer analogy to analysis.
It might be hoped that the study of human history would assist, but the
record of history is ambiguous. A striking instance of this ambiguity
is to be found in Professor Carr Saunders’ book on the Population
Problem. In the course of a temperate and on the whole well-balanced
discussion of the racial factor in history, Carr Saunders remarks that
the
“Nordic peoples are mostly Protestant and the Mediterranean peoples
mostly Catholic and Greek. The fact,” he continues, “that during
the Reformation a choice was set before most European nations as to
what religion should be adopted--the issue hanging in the balance
for some time in many places--seems to indicate that the conditions
were more or less equalized and the adoption of the Protestant
religion by the Nordic type was influenced by certain innate
characters attaching to that type.”
Even if we make a very generous allowance for the genetic homogeneity
of the Nordic and Mediterranean populations in mediæval times, an
entirely different interpretation of the same facts is equally
plausible. At the time when Christianity received official recognition
the countries to which Carr Saunders refers as predominantly Nordic lay
on the fringe of Roman Imperial domination or completely outside it.
The process of christianizing the Nordic geographical region was still
in its infancy when the Holy Roman Empire embarked on its ephemeral and
inglorious career. It was hardly complete, when controversy within the
Western Church began to assume sinister proportions. With the exception
of the Saxons the conversion of the Germanic peoples, including the
Frisians, took place in the early part of the eighth century. The
official conversion of Saxony occurred about A.D. 800. Christianity
was accepted by the ruling powers of Denmark towards the end of the
tenth century and by those of Norway and Sweden at the beginning of
the eleventh century. The conversion of East Prussia, Latvia and
Pomerania occurred during the twelfth century, and the conversion of
Lithuania did not occur until the middle of the fourteenth century. In
those countries which Christianity penetrated last of all the conflict
between the ruling houses and the temporal claims of the Papacy was
generally most acute. Where reformers could seek protection in the
clemency of monarchs at loggerheads with the Pope, they spread their
doctrines successfully. Where there only existed a religious movement,
it was speedily extinguished. The Reformed doctrines spread in those
countries where Christianity had been more recently introduced, and
where the political sovereignty of the Pope and the economic power
of the Church as a landowner were least firmly entrenched and least
agreeable to the secular authorities. Catholicism had taken root in
the ancient civilization of the Mediterranean region, when the Nordic
peoples were outside the pale. If it is true that the Nordic peoples
gravitated to Protestantism, it is equally true that they happened
to inhabit the geographical region most remote from Rome. There is
no reason to suppose that their choice of locality was determined by
any characters peculiar to their type or relevant to the progress of
theological discovery.
In seeking to make allowance for the significant factors of man’s
social environment there is no body of accredited information to which
the geneticist can turn. There are as many schools of psychology
as there are schools of philosophy. The introspective psychologist
approaches social behaviour from a purely teleological standpoint,
interpreting the means in relation to the end it fulfils. The
behaviourist adopts a mechanistic attitude, seeking to interpret the
end as predestined by the means. One speaks of a directing intelligence
and instinctive action. The other speaks of intelligent behaviour and
unconditioned response. Between the two schools there is a great gulf
fixed. It is that which separates the philosophy of Plato from the
teaching of Democritus. It is not merely a difference of perspective
or of minor issues. Such differences exist in an exact science. The
psychologists disagree about the very nature of inquiry into the basis
of social behaviour; and there is no immediate prospect that they will
come to terms. Meanwhile the eugenist finds himself impaled on the
horns of a dilemma. The methods of animal genetics are mechanistic;
but the behaviourist is suspicious of the genetical standpoint; while
the introspective psychologist fails to define the characteristics of
social behaviour in a form suitable for genetic analysis.
When Binet and Terman published their psychological tests, it seemed
that there was a brighter prospect for the objective study of mental
inheritance. Of late the psychologists themselves have begun to adopt a
less confident attitude. Recently the Stanford school of workers have
conceded a conservative allowance of 20 per cent. for the influence of
home environment on the intelligence quotient. We have no grounds for
believing that the ingenious system of home ratings adopted by Miss
Burks (1927) in this investigation include all the significant factors.
Consequently this figure represents a minimum. The Chicago school
have investigated the intelligence quotients of foster children, and
adopt an even more sceptical attitude to the value of the I.Q. as a
measure of genetic endowment. Tallman has investigated the intelligence
quotients of sixty pairs of identical twins. It was found that the mean
difference between pairs of brothers and sisters of different ages on
the one hand and pairs of non-identical twins on the other was larger
than the difference between pairs of non-identical twins and pairs of
identical twins. Accepting the most conservative allowance, it may
be stated with some confidence that the contribution of environment
to the intelligence quotient is at least as large as the recorded
differences between racial and occupational groups subject to different
environmental influences.
For two generations eugenists have been writing about mental
inheritance. As far as I am aware Professor MacDougall alone has
pointed out that the attempt to formulate a concept of mental
inheritance raises a very formidable issue which challenges the
foundations of current biological philosophy. He himself faces the
difficulty by returning to the Lamarckian fold. Lamarck’s position
was at least consistent. He conceived heredity in mental terms. His
theory was teleological throughout. Galton was not consistent, and
his disciples have been less so. Since Weismann’s time the study of
heredity has become more and more explicitly materialistic. To the
modern geneticist heredity is one aspect of the physical process
involved in the production of a new unit of living matter. His
hypotheses are conceived in physical units. The gene has space-time
dimensions. Mental inheritance is a meaningless collocation of words,
unless it is possible to bring the concept of mentality within the
mechanistic framework. That is what the behaviourist school in
psychology has undertaken to do. The future of social biology depends
on the success which attends their efforts.
Fifty years have passed since Francis Galton published _Hereditary
Genius and An Enquiry into Human Faculty_. Since then there have been
notable changes in the attitude which scientists have adopted both
towards heredity and human faculty. The work of Mendel, Bateson and
Morgan has enormously enriched our knowledge of hereditary transmission
in animals. The work of Loeb, Sherrington and Pavlov has opened up new
horizons in the study of animal behaviour. The biological analysis
of social behaviour presupposes that both methods can be brought
to bear upon it. It may be premature to adopt a confident attitude
to the prospects, but it is legitimate to state that there is no
likelihood of solving the problem which Galton propounded so long as
eugenists continue to regard it as the exclusive prerogative of the
evolutionist. The enthusiasms engendered first by the reception of
Darwin’s hypothesis and subsequently by the spectacular advances which
have resulted from Mendel’s discovery, encouraged the eugenist to adopt
an extremist attitude. New and no less noteworthy developments in the
physiology of the nervous system have encouraged the behaviourist to go
as far as possible in the opposite direction.
It is not difficult to understand how this has happened. In Galton’s
time the analysis of animal conduct had not progressed beyond the
recognition of those simple units of behaviour which Pavlov calls
“unconditioned” reflexes. The scratch reflex evoked on stimulating
the lumbosacral region in the spinal dog is an example of this type.
Given the same external situation, it can be elicited in any member of
the canine species. There are therefore two principal factors which
determine the scratch reflex. One is the immediate stimulus. The other
is the _inherited_ structure of the nervous system. Simple reflexes
of this kind play very little part in man’s social behaviour; but
modern physiology recognizes a more complex type, which Pavlov calls
the “conditioned” reflex. The study of these promises to meet some of
the requirements of a biological analysis of man’s social behaviour.
The conditioned reflex is not characteristic of all the members of a
species subjected to the same immediate situation. It depends upon
the time relations of other stimuli which have previously acted upon
the organism. Within certain limits it is possible both to predict
the outcome, when the time relations of previous stimuli are defined,
and to account for a totally different pattern of behaviour in two
individuals who inherit the same neuromuscular organization. It was
natural that Galton’s generation should harp on the hereditary basis of
social conduct. They were beginning to understand a type of behaviour
in which the genetic factor is the significant variable, and to apply
their knowledge to the interpretation of “instinct” in animals. It is
not surprising that the behaviourists should adopt the opposite point
of view. They are beginning to understand a type of behaviour in which
the genetic factor is less important, and to apply the new methods to
the study of Man himself.
Even if the behaviourist reaction goes too far in neglecting the
genetic aspect of social behaviour, it will have performed one
considerable service to social biology. Biology and sociology coincide
in the attempt to distinguish what characteristics of human society
are related to those characteristics which man shares with all other
animals, and what characteristics of human society are related to
characteristics which man shares with no other animals. The geneticist
is only concerned with the former, since the material basis of
inheritance in man and other animals is substantially the same. It is
the physiologist who is brought into contact with the characteristics
which distinguish man from other animals. Man inherits an immensely
developed forebrain; and this circumstance frees him from many of
the restrictions which heredity imposes upon the brute creation. The
forebrain is the structural basis of conditioned behaviour; and what
distinguishes man pre-eminently from all other animals is the extent
to which his behaviour is conditioned by previous experience. A truly
biological analysis of human society must build on the recognition that
man is the most teachable of animals. This is a profound truth which
the eugenist has neglected. The behaviourist has reopened the door
which the eugenist closed. The selectionists succeeded in presenting
evolution in a form acceptable to their contemporaries. Man was dragged
down from his celestial eminence. His place among the brutes became an
accepted commonplace of the naturalistic outlook. Sentence had been
passed upon him. Henceforth he must live within the prison of his
own genetic limitations. Before the portals of his primeval dungeon
Heredity stood with a flaming sword. In his new surroundings Man could
still demand a retrial, because selectionism was the product of his
own forebrain. That trial is still in process. Science has not yet
promulgated its final verdict. Galton conducts the prosecution. Watson
cross-examines for the defence. Man is released on bail, pending the
result of his appeal.
In English law there is a wholesome provision which forbids the public
discussion of evidence until the case is closed. In science there is
no penalty for contempt of court. It is a pity that there is not. The
discussion of the genetical foundations of racial and occupational
classes in human society calls for discipline, for restraint and for
detachment. Nothing could make the exercise of these virtues more
difficult than to force the issue into the political arena in the
present state of knowledge. This is precisely what the eugenist has
done. The result is that social biology is encumbered with a vocabulary
of terms which have no place in an ethically neutral science; and a
growing literature of inquiries repeats all the shortcomings which
animal genetics has outgrown. Of these shortcomings anecdotalism is
the least. All biologists recognize the disastrous consequences of
constructing evolutionary hypotheses on the testimony of the stock
breeder and the pigeon fancier. Only an undue haste to establish
conclusions which can be made the basis of legislation has arrested the
development of social biology in its anecdotage.
Quotations from well-known contributions by eugenic writers will
exempt me from the charge of overstating the danger to which I
allude, when I speak of the anecdotal method. Few would deny the
desirability of shedding further light on the contribution of heredity
to feeblemindedness. It is the concern of the social biologist to do
so. Goddard’s familial studies on this problem have been extensively
quoted by eugenic writers. In his investigation several hundred
individuals in the Vineland training-school for mental defectives were
classified by the Binet test as morons. Goddard conducted inquiries
into the family histories of these individuals, and records them
in his book. He concludes that a certain type of feeblemindedness
is determined by a single Mendelian factor. This conclusion is
logically untenable apart from the evidence, because his criterion
of feeblemindedness was a segment arbitrarily cut off from a normal
distribution curve; but the method which he employs rather than the
conclusions he infers is the issue to which I would direct attention.
Mendel initiated a new epoch in genetics by clearly defining the nature
of the character which he studied. That practice is the keystone of
the science which has developed from his pioneer labours. The Binet
test may be legitimately employed as a means of providing an objective
definition of feeblemindedness; but since the Binet test is a recent
innovation, it is obvious that Goddard could not employ it to identify
feeblemindedness in the parents and grandparents of his cases at the
time of writing. The method he adopted is stated in the following
passage (_Feeblemindedness_, p. 20):
“The ease with which it is sometimes possible to get satisfactory
evidence on the fifth generation is illustrated in the Kallikak
family. The field worker accosts an old farmer--‘Do you remember
an old man Martin Kallikak (Jr.) who lived on the mountain edge
yonder?’ ‘Do I? Well I guess. Nobody’d forget him. Simple, not
quite right here (tapping his head), but inoffensive and kind. All
the family was that. Old Moll, simple as she was, would do anything
for a neighbour. She finally died, burned to death in a chimney
corner. She had come in drunk and sat down there. Whether she fell
over in a fit or her clothes caught fire nobody knows. She was
burned to a crisp when they found her. That was the worst of them,
they would drink. Poverty was their best friend in this respect,
or they would have been drunk all the time. Old Martin could never
stop as long as he had a drop. Many’s the time he’d rolled off of
Billy Parson’s porch. Billy always had a barrel of cider handy.
He’d just chuckle to see Martin drink and drink until finally he’d
lose his balance and over he’d go.’”
At the conclusion of this recital Goddard asks, “Is there any doubt
that Martin was feebleminded?”
It may at least be said for Goddard’s work that it contains some
presumptive indications that genetic factors play a significant part
in determining certain kinds of feeblemindedness. It is doubtful
whether any plausible conclusions can be drawn from the dreary history
of the Jukes. In his monograph on the Jukes in 1915, Estabrook only
ventures to proffer one definite statement concerning hereditary
transmission in the Jukes family. It is that “there is an hereditary
factor in licentiousness.” I have searched through his memoir for a
single indication of the way in which he defines licentiousness and its
allelomorphic opposite chastity. Out of a large number of monotonously
similar family case histories I shall quote the only one which contains
any suggestion of the meaning he attaches to the latter. This (Case G)
is as follows:
“A cousin mating of chaste individuals was followed in the first
generation by no licentiousness. In the second generation from the
cousin mating no licentiousness appears, although the father of
one of the children of this generation had cohabited previous to
marriage. Their one daughter was chaste, but she has one daughter
brought up in a good home free from bad influences, who was very
erotic but is at present chaste. The third child of this cousin
mating of chaste people, Addie, married a man who had acquired
syphilus and had one son an inefficient syphilitic who died of
tuberculosis. Addie died of syphilis at 20. The fourth child Alta
V 78 who was always chaste, married but had no children. Horace
the only other child of Alfred who reached maturity was reputed
chaste but was intemperate: he married a chaste woman and had nine
children, all of whom are chaste.”
Before we take the risk of wrecking the machinery of social biology
by exceeding the speed limit of rational inquiry, it is desirable
to ascertain the reasons for such haste. Dr. Estabrook has recorded
his own reasons in quantitative terms. “Dugdale estimated a loss to
society of $1,250,000 by the Jukes family from 1800 to 1875. The loss
to society caused by mental deficiency, crime, prostitution, syphilis
and pauperism of these 2,800 people is now estimated at $2,093,685. If
the drink bill is added, this total becomes $2,516,685.” The reason
for this addition will be more apparent to a prohibitionist than to a
brewer. Mr. Chesterton might retort by asking whether there are no idle
young clubmen in New York whose annual upkeep is equivalent to the loss
entailed by the Jukes during the last century and a half. Deplorable
as the history of the Jukes may be, its consequences to civilization
may be less disastrous than half an hour’s conversation between a
manufacturer of armaments and a newspaper proprietor. In such matters
private values influence our opinions more than those issues which can
be discussed in the public forum of science. Estabrook’s arithmetic
does not convince me that we should exchange the experimental and
sceptical temper of scientific inquiry for the facile slogans of the
parliamentary candidate.
The eugenic movement was founded to encourage “the study of agencies
under social control that may improve or impair the racial qualities
of future generations either physically or mentally.” That aim might
be taken as a statement of the scope of social biology, when due
allowance is made for the full requirements of a scientific inquiry
into the nature of “mental inheritance.” There are a few prominent
eugenists who have adhered to this praiseworthy and modest programme.
Professor Carr Saunders who has been prominently associated with
the eugenic movement in England has consistently expressed himself
with discrimination and restraint on the complex issues which the
genetic structure of human society involves. If I am disinclined
to follow him in the alarmist attitude which he adopts towards the
differential fertility which has accompanied the recent decline of the
European birth-rate, I entirely agree with him in recognizing that the
differential fertility of occupational groups is a matter for careful
and comprehensive investigation. To make any satisfactory predictions
about the outcome of the present decline it is necessary to ascertain
what factors have contributed to the reduction of the birth-rate, what
genetic differences distinguish different occupational groups, and how
such differences are transmitted. The impressive array of evidence
which Beveridge, Stevenson and Carr Saunders have presented strongly
suggests that the spread of contraceptive practice has been the main
factor in the decline of the birth-rate. The German and Swedish data of
Grotjahn and Edin point to the conclusion that contraceptive practice
is spreading to all sections of society. If this is so the problem
of differential fertility is solving itself. Of genetic differences
which distinguish occupational groups we have no definite information.
Even if we had, it would be necessary to know how such differences
are transmitted before prophesying disaster. Haldane’s mathematical
analysis of the effect of selection shows that a selective process
must be continued for a very long period in order to produce an
appreciable effect on the distribution of a character which depends on
the co-operation of several recessive genes. An attitude of calvinistic
gloom towards the future of human society is not a necessary
consequence of the biological study of human society.
In discussing the influence of eugenic propaganda in this essay I
have been primarily concerned with the dangers of speculating upon
questions whose philosophical importance is less apparent than their
practical interest. I trust that I have made it abundantly clear that
I am in no sense hostile to eugenics as defined above. Were I to
indulge in the luxury of stating a purely personal opinion about the
genetics of human society, it would be somewhat as follows. It is
probable that extremes of intellectual accomplishment or defect are
significantly determined by genetic variation. It is highly unlikely
that extreme types of defective are reproducing disproportionately. It
is also doubtful whether genius has ever been biologically fertile.
Between the two extremes there is probably a neutral zone in which
somatic variability plays a larger part than genetic differences in
determining social behaviour. At present it is impossible to assess
with precision the mean genotypic endowment of different social
groups, whether occupational or racial. Even if it were, the precise
significance of the mean would be problematical. I think it highly
unlikely that such mean differences as may exist provide any basis for
establishing new social barriers or reinforcing old ones, still less
for curtailing opportunities of education and the exercise of political
responsibility. On the other hand it is not unlikely that there does
exist a section of genetic types on the borderline of extreme defect
not segregated from the rest of the community and more fertile than
others of the same social grade. With Mr. Chesterton I am inclined to
doubt whether they represent a larger proportion in one social class
than in any other. Unlike Mr. Chesterton I see no reason why society
should not deal with this issue as a genetic problem, when it is
clearly proved to be a genetic problem. Indeed I think it arguable that
it would be wiser not to take any risk of encouraging the feebleminded
to breed. At present I see no way of stopping them.
There can be no disagreement concerning the desirability of exploring
every avenue in human genetics. This cannot be done without enlarging
the scope of the official census with the support of a sympathetic
government. Hitherto Eugenic propaganda has been dominated by an
explicit social bias which, in England, can only serve to render the
Eugenic standpoint unpalatable to a section of the community which for
good or ill seems to be assuming the rôle of a governing class. The
greatest obstacle to the spread of a sane eugenic point of view is the
eugenists themselves. By recklessly antagonizing the leaders of thought
among the working classes the protagonists of eugenics have done their
best to make eugenics a matter of party politics, with results which
can only delay the acceptance of a national minimum of parenthood.
These last remarks I repeat are a statement of purely personal opinion.
Biologists share the human frailty which prompts all of us to entertain
beliefs fortified by insufficient evidence; but there is no reason why
the biologist should fail to make it clear, when he is speaking as a
professional biologist and when he is speaking as a private citizen.
From a purely scientific standpoint the problem of human inheritance
can only be regarded as a virgin field in which the prospects of an
early and abundant harvest are by no means bright. I believe that the
eugenists have performed a useful task in emphasizing the need for a
biological analysis of human society. The furtherance of that task will
not be promoted by propaganda which overstates the achievements of
the present, while underestimating the difficulties which lie ahead.
Evolutionary inquiry was brought to an end in ancient Greece, when
philosophy became the handmaiden of politics. Further progress was
checked when philosophy became the bondservant of theology. Eugenics
like Greek philosophy derived its first impulse from natural science.
It soon entered into alliance with the politician. It is fast finding
its most stalwart supporters among the clergy. It can only realize
the aims of its founder by bringing the science of genetics into
closer relationship with other methods of studying human biology and
annulling the marriage of biological inquiry with political propaganda.
As a private citizen the biologist is entitled to his own opinions
concerning the merits of sterilizing the unfit, just as he is entitled
to his own opinions on the Single tax or the advantages of capital
punishment. Such opinions usually belong to his private world. In
his public capacity, as a biologist, he is primarily concerned with
sterilizing the instruments of research before undertaking surgical
operations upon the body politic.
PART III
HOLISM AND THE PUBLICIST STANDPOINT IN PHILOSOPHY
SUMMARY
When the conclusions of physicists are supplemented by the enquiries
of the biologist we are led to a schematization of experience which
permits us to discuss the nature of matter and life on a neutral
ground. This neutral ground is the _public world_ of science. It
represents what is significant for the purpose of discourse. Idealistic
philosophers have assumed the nature of reality as the goal of
philosophy; but the concept of reality is essentially equivocal. For
the purpose of discourse we have to assume that the neutral ground
is the real thing. In private we are at liberty to reject this view.
Temperament decides which of these alternatives we adopt. There is
therefore no hope of arriving at universal agreement in discussing the
nature of reality. To the introvert reality resides in the domain of
mystic experience. To the extrovert the public world is the nearest
approach to a complete representation of reality which our limited
range of receptor organs permits us to construct. The belief that
philosophy can settle the nature of reality, and that it is possible to
arrive at universal conclusions independently of the methods of science
and mathematics arose in the period of decadence of Greek philosophy.
It developed in modern Europe under the influence of ecclesiasticism.
Freed from the bondage of clerical control, philosophy must undertake
the more modest task of discussing what characteristics of belief
determine their communicability or _publicity_, and indicating how the
problems of existence can be resolved into their public and private
components. From this standpoint educational theory must be based on
a recognition of the respective spheres of _publicity_ and _privacy_.
Organized religious belief and ritual is based on a confusion between
the two. The same confusion exists in the pragmatist philosophy.
IX. BIOLOGY AND HUMANISM
“But the mortallest enemy unto knowledge, and that which hath
done the greatest execution upon truth, hath been a peremptory
adhesion unto authority; and more especially, the establishing of
our belief upon the dictates of antiquity. For (as every capacity
may observe) most men, of ages present, so superstitiously do look
upon ages past, that the authorities of the one exceed the reasons
of the other. Whose persons indeed far removed from our times,
their works, which seldom with us pass uncontrolled, either by
contemporaries, or immediate successors, are now become out of the
distance of envies; and, the farther removed from present times,
are conceived to approach the nearer unto truth itself. Now hereby
methinks we manifestly delude ourselves, and widely walk out of the
track of truth.”--Sir Thomas Browne, _Pseudodoxia Epidemica_
§1
Evolution does not enable us to make any spectacular predictions
which can be verified here and now. Its importance lies in satisfying
our curiosity about human origins in a manner consistent with the
present state of scientific knowledge. It provides a philosophical
framework for biological enquiry on the one hand and for our attitude
to the problem of human destiny on the other. From a purely technical
standpoint Darwin’s specific contribution to the evolutionary doctrine
was the hypothesis of natural selection. The hypothesis of natural
selection, in the form in which Darwin stated it, has been modified out
of all recognition to accommodate later enquiries into the nature of
heredity and variation. Such enquiries did not receive their impetus
from the _Origin of Species_. They followed the course prescribed by
Mendel’s experiments upon the kitchen pea. How then has it come to
pass that Darwin has earned a position of pre-eminence only comparable
with that of Newton in modern times? Is not the answer that Darwin is
the only great natural philosopher who has emerged, since the time of
Aristotle, from the ranks of the biologists? When the fullest allowance
is made for the inadequacy of contemporary knowledge to meet all the
demands of the evolutionary problem, what still distinguishes Darwin’s
contribution from that of his numerous predecessors in the same field
is the consistency and thoroughness with which he set out to explore
the implications of evolution in every department of biological
information available at that time. By so doing he laid the foundations
of a new humanism akin to science, and created a philosophical issue
whose magnitude has only become apparent since the rise of the
behaviourist school in psychology. Evolution took the discussion of
human affairs out of the hands of the humanistic philosophers, and
brought it within the legitimate domain of scientific method.
From the dawn of philosophical controversy two opposing tendencies
have competed for mastery. One is based upon confidence in the
testimony of our receptor organs. The other mistrusts the evidence of
the senses. One relies on patient observation. The other appeals to
axioms which require no proof. One has its impulse in curiosity about
Nature. The other is preoccupied with human obligations. Between the
two extremes there have been many makeshifts. As one has fallen into
discredit, another has taken its place. The only permanent feature
of philosophical discussion is the impossibility of effecting a
permanent reconciliation between those who have called themselves, at
different periods of history, materialists and idealists, nominalists
and realists, empiricists and transcendentalists, mechanists
and vitalists, to emphasize some new aspect of a fundamental
incompatibility. In the distinction between publicity and privacy it
has been suggested that this antinomy does not necessarily reside
in the system of nature. It arises because our curiosity exceeds
our information. Up to a certain point we succeed in pooling our
experiences by the method of science. In so doing we construct the
public world. The method of science has achieved its most conspicuous
success in dealing with inanimate objects and with the brute creation.
To the few who are genuinely interested in these things the extent of
our knowledge has always seemed of more importance than the magnitude
of our ignorance. Hence there have always been philosophers of a type
which, for want of a better term, may be called _materialistic_. The
majority of people are not interested in natural objects except in
so far as the knowledge which science confers contributes to their
personal comfort. Man is pre-eminently interested in himself. So long
as science cannot satisfy that curiosity his private and personal
values assume a greater importance than the academic hypotheses of
science. Philosophers who teach us to distrust the guidance of our
sense data flatter our egotism, and soothe our vanity. Science cannot.
On the other hand science can supply us with aviation, broadcasting
and twilight sleep. Transcendental philosophy can only offer us the
good life. The politician distrusts the mechanist, because Science
provides no concept of divine right to fortify social privilege. He
cannot go all the way with Parmenides and identify the way of the
senses with the way of error, because scientists are too useful.
The only philosophy for the plain man who wants a plain answer to
a plain question is some sort of compromise between the standpoint
of transcendental metaphysics and mechanistic science. Since the
sixteenth century humanistic philosophy has been dogged by the problem
of accommodating man’s interest in the world around him with his
interest in his own person. Worldly interests compel civilized man to
recognize the claims of science up to a certain point. Egotism prompts
him to demand some supernatural sanction for the vagaries of his own
social conduct. For three centuries traditional philosophy has been
haunted by the possibility that science might in the end succeed in
satisfying man’s curiosity about his own nature. Darwin made that
possibility the explicit concern of scientific enquiry. From mediæval
times all attempts to effect a reconciliation between the empirical
standpoint and transcendental values have been concerned with defining
separate spheres of influence in which science and metaphysics can
operate without mutual interference. On that basis philosophy is still
taught in our universities to-day. Darwin’s _Descent of Man_ challenged
the complacent dualism which had permitted humanistic philosophy
and utilitarian science to pursue an independent course from the
Renaissance to the middle of the nineteenth century.
At every stage in the advance of scientific knowledge a new
system has arisen to conserve some fragments from the wreckage of
supernatural beliefs. There have been three outstanding attempts
to effect a compromise between observation and inspiration. The
systems of Aristotle, of Descartes and of Kant each exhibit features
characteristic of the state of contemporary scientific knowledge. Each
has a peculiarly interesting significance in the history of biological
science. The system of Aristotle was the last will and testament
of Greek biology. The system of Descartes was finally overthrown
by the evolutionary theory. The system of Kant is predestined to a
similar doom, when professional philosophers are prepared to face the
disquieting consequences of modern research on the “labyrinthine organ”
and Sherrington’s work on the “muscular sense.” If it is too early to
predict the fate of holism, it is instructive to reflect on that of its
predecessors.
§2
Aristotle undertook the task of finding a place for science in a
civilization in which scientific enquiry was approaching its decline.
His problem was simplified by the circumstance that the conflict
between teleology and mechanism had arisen as a conflict of interest
rather than interpretation. Burnet insists that the idea of purpose
only emerged at a comparatively late date in the history of Hellenic
science, and the more recent researches of Cyril Bailey emphasize the
same aspect of the incompatibility of natural and moral philosophy
in ancient Greece. Greek philosophy had inherited from the Hesiodic
cosmogony the belief that Chaos was the beginning of all things, gods
and men alike. It was unfettered by the Chaldean Fall and the doctrine
of creative providence. Aristotle’s system was therefore an attempt to
harmonize two tendencies which had come into being independently of
one another. One begins with Thales. It bore fruit in the brilliant
speculations of Leucippus and Democritus. It survived after Aristotle’s
death in the mechanical discoveries of the Alexandrian school. In
the poem of Lucretius it made a final gesture of august rhetoric. To
modern civilization it bequeathed the indestructibility of matter, and
the atomic concept which was revived by Gassendi in the seventeenth
century. Its rival was anti-scientific and mystical. It diverted
enquiry from the observation of nature to the duty of man. It was
preoccupied with the good life, with the soul and with the hereafter.
It began with the Eleatics and the Pythagoreans. It gave birth to the
school of Plato; and its influence survived long after the extinction
of Hellenic civilization. Through Philo Platonism transmitted the Logos
to the Nazarenes, and at a later date the neoplatonists equipped the
Church with the apparatus of the Trinitarian controversy. It completed
its contribution to Western culture in the Council of Trent, when the
mystery of human life, death and duty were placed for all time on a
firm foundation of deductive reasoning.
The success of Platonism was assured by the powerlessness of Greek
materialism to satisfy the requirements of Greek politics. The plain
man wanted to know whether the wise man will obey the laws, if he
knows that he will not be found out? With transparent honesty Epicurus
could only reply that a simple answer is difficult to find. The benign
and tolerant humanism which Epicurus grafted on the soil prepared by
the atomists was ill suited to flourish in the stern climate of the
military state. Like holism, Aristotle’s system was a shrewd blending
of science and statesmanship. It enabled its author to combine a
personal predilection for natural history with a political partiality
for slavery.
Aristotle borrowed from Plato the doctrine which identifies the φυσις,
or real nature with the best or most normal condition of a thing. He
rejected the respect for mathematics which Plato borrowed from the
Pythagoreans, and incorporated Plato’s teleology in his theory of the
physical world. One disastrous effect of this may perhaps be seen
in the neglect and preservation of more ancient work. Empedocles is
known to have made observations on respiration and the movement of the
blood. It would seem that he had recourse to experiment of a crude
kind. One fragment of his writings contains a hint that he came very
near to anticipating Torricelli and Harvey. The details have been lost.
Empedocles also put forward a theory of vision. He held that the eye
contains fire. Sight is produced when the fire within the eye goes
forth to meet the object. A hypothesis so well adapted to the view
which interprets life by “correlating the initiation of the activity
with its end” was, as might be expected, immortalized by Plato to the
calamity of physical and physiological enquiry. Science had a long road
to traverse before men learned the truth of Nietzsche’s statement that
“the most valuable knowledge is always discovered last, but the most
valuable knowledge consists of methods.”
The fundamental incompatibility of the naturalistic and Platonic
attitude to the Nature of Life is illustrated by the following passage
from the writings of a contemporary philosopher, Professor Wildon Carr:
“It is wholly inadequate to classify natural objects into the inert
and the living, into objects which are not responsive and objects
which are responsive to external impressions, and then to seek to
specify the property or character which differentiates the one
class from the other. Life is a perfectly definite and distinctive
phenomenon. It is not a thing, neither is it the character of
a thing. It is a purposive activity exercised within clearly
ascertainable limits and having a definite range. I use the term
purposive without any implication of awareness. Living activity
is purposive in the meaning that it can only be understood by
correlating the initiation of the activity with the end. The nature
of the activity is plainly recognizable, however difficult it may
be to conceive the agent, agents or agency which the activity
implies.... Life is individual: it exists only in living beings,
and _each living being is indivisible, a whole not constituted of
parts_.”
The concluding remarks of this passage are somewhat reminiscent of the
Athanasian creed, the germs of which were actually derived from the
neoplatonists. It displays the sterilizing influence of the Platonic
teaching in a peculiarly explicit form. If the words quoted in italics
were actually true, experiments carried out daily by medical students
in physiological and pharmacological laboratories would be impossible.
The physiologist takes the living machine to pieces and studies the
properties of its several parts. The experimental embryologist can
put it together again. Ross Harrison grafts the head end of a tadpole
of one species on to the tail end of a tadpole of another species.
The progress of modern biology has been made possible by the implicit
rejection of the attitude which Professor Wildon Carr advocates; and
this is not merely true of the growth of experimental physiology as
a quantitative science. In our generation Bergson has rehabilitated
the evolutionary doctrine in teleological language. Its history very
clearly shows that the rise of the evolutionary hypothesis in its
modern form is traceable to the liberation of biological enquiry from
Aristotelean teleology. Two centuries of research, fertilized by
the experimental temper which Vesalius reintroduced into the study
of medicine, paved the way for a new school of naturalists in the
eighteenth century. Ray and Linnæus took up the comparative study of
animal life where Aristotle had left it. At a later date Cuvier, Milne
Edwardes and Owen founded a school of comparative anatomy which--unlike
post-Darwinian morphology--made the issue of experiment the final
court of appeal. It was thus that Darwin and Wallace brought to the
discussion of Man’s place in Nature a mass of new data, accumulated in
the process of displacing the teleological bias under whose influence
Greek biology steadily declined. It is futile to blame Aristotle for
the influence which his particular form of compromise exerted on the
history of biology. In Aristotle’s time it was impossible to say: “Here
is a property of living matter, the teleological attitude leads us
to make such and such predictions; quantitative analysis leads us to
contrary conclusions: let us submit the merits of the two methods to
the issue of experiment.” Aristotelian biology was not an experimental
science.
When Aristotle infused into Greek biology the teleology of Platonism,
natural science had already progressed as far as it was destined to
advance without coming into conflict with teleological presumptions;
but the inevitability of the conflict was not yet apparent, and
does not emerge as a clearly defined issue in Greek philosophy.
Greek materialism, like modern science, was the offspring of secular
curiosity. For this reason it is easy to trace the germs of modern
hypotheses in the speculations of the ancients. It is more difficult
to determine how far such analogies are merely verbal. The extent to
which the Greeks had recourse to experiment has given rise to lively
controversy. We are more familiar with their beliefs about nature than
with the evidence on which they relied. To reconstruct the scientific
knowledge of Anaximander and Empedocles from the fragments of their
writings which remain is a task no less formidable than that of a
future historian who has nothing but the torn pages of a Harmsworth
encyclopædia to provide evidence of contemporary science. The fact
remain that the scientific knowledge of the ancients lacks two
features which are highly characteristic of modern enquiry. Greek
science was static. Having no means of measuring short intervals
of time, the Greek could make little use of dynamical notions. The
mathematical technique for dealing conveniently with dynamical
calculations was not evolved until Greek geometry was supplemented
by the universal arithmetic of the Arabs. Galileo’s dynamics was the
death-blow to Aristotelian teleology. To the Greeks time relations were
philosophical enigmas. They had not as yet become objects of scientific
enquiry. Modern mechanistic biology lays emphasis on _process_. Greek
biology was still dominated by _structure_. This preoccupation gave
rise to the distinction between form and substance which assumes a
prominent place in the Aristotle of the schoolmen, and persisted
in modern science, until the dynamical concept of electromagnetic
mass was put forward. A second characteristic which distinguishes
contemporary science from the natural philosophy of the Greeks has
been emphasized less by historians of science. This may be because
astronomy and mechanics were developed by the school of Alexandria in
close association with mathematics. That brilliant but short-lived
phase in the science of antiquity was post-Aristotelian. Astronomy was
the only branch of natural science which had attained the precision of
measurement in Aristotle’s time.
The distinction between Aristotelian vitalism and the modern biological
standpoint is most apparent in the attitude which Aristotle adopted to
quantitative investigation. “Mathematical accuracy of language,” he
declares, “is not to be required in all things, but in those things
that do not involve any connexion with matter. Wherefore such is not
the natural (alternatively _physical_) mode of discovering truth, for
perhaps the whole of Nature involves matter. Therefore first must we
investigate what Nature is. For in this way also will it be evident
about what only natural science is conversant, and whether it is the
province of one science or many to speculate into causes and first
principles.” This passage occurs in the first book of the Metaphysics.
There are other passages in which the same point of view is expressed.
They show conclusively that Aristotle was not content with ignoring the
connexion between mathematics and science. He definitely asserted that
the quantitative study of natural phenomena is not the correct one.
In this he went further than Plato. While Plato despised the study of
physics and biology, he recognized the vital dependence of astronomy
on mathematics and valued its pursuit. The standpoint which Aristotle
adopted is comprehensible. His interest in nature was mainly that of
the naturalist. He did not study living creatures in the belief that by
so doing he would be able to predict their behaviour. That possibility
only emerged into prominence when Lavoisier and Laplace brought the
thermometer and the balance to the study of respiration. By then the
spectacular progress of physics had necessitated a new adjustment of
the claims of moral and natural philosophy. The philosophy of Descartes
liberated biology from developing within the limitations prescribed by
the Aristotelian system.
Two events contributed significantly to the situation which Descartes
faced at the beginning of the seventeenth century. The period which
intervened between Aristotle and Descartes witnessed the rise of
Christianity and the origin of a new cultural synthesis within the
world of Islam. At Alexandria natural science and mathematics still
flourished, when Christianity became the official faith of the
Roman Empire. Five centuries after the death of Aristotle Diophantus
made what seems to have been the first definite contribution to the
development of algebraical analysis. Alexandrian science came to an end
when “on a fatal day in the holy season of Lent,” Hypatia the expositor
of Diophantus “was torn from her chariot, stripped naked, dragged to
the church, and inhumanly butchered by the hands of Peter the reader
and a troop of savage and merciless fanatics.” Two centuries later what
was spared by the religion of Cyril was consigned to the flames by the
victorious armies of Islam.
While Christianity and Mohammedanism were competing to appease the
deeper needs of mankind, the genius of a dark-skinned people was
preparing the stage for a rebirth of European culture. Before the
destruction of a second library of Alexandria the Greek learning had
filtered into the middle East through the hospitality which the Persian
court extended in turn to the banished Platonists, the Jews and the
heretic Nestorians. In India Brahmagupta and his successors had applied
themselves to the same problems which Diophantus had assailed. Half
a century before the foundation of the University of Baghdad Hindu
astronomical tables and the rhetorical algebra of the far East had been
introduced into Persia. By the beginning of the ninth century the works
of Ptolemy, Euclid, Hippocrates and Aristotle had been translated into
Arabic. At the end of the tenth century the Moorish culture was firmly
established in Europe. In the universities of Cordova, Seville and
Toledo, the study of medicine and mathematics flourished side by side.
The medical schools of Italy and France were outposts of the Moorish
culture in the twelfth and thirteenth centuries. The Moors extended
the Alexandrian pharmacopeias; and advanced the study of anatomy.
Jewish missionaries of the Moorish culture brought the tradition of
dissection into Italy. From Arabic manuscripts Italy first made contact
with the resources of Greek science. Arabic learning transmitted the
texts from which ecclesiasticism imbibed its taste for metaphysics,
and at the same time contributed two influences subversive to the
Aristotelian system. It gave birth to chemistry as an experimental
science, and it developed the beginnings of syncopated algebra. The
invention of algebra made possible the efflorescence of physics when
Greek geometry had long since completed its task as the midwife of
mathematical astronomy.
From the fact-loving temper of Aristotle the naturalist Arabic
curiosity had absorbed all that could be used as a basis for scientific
enquiry. In the Sorbonne the Platonic ingredients of his system brought
fresh grist to the mill of theological controversy. By seeking for
“causes and first principles,” Aristotle in his own words had made
philosophy the “divine science.” As the divine science it was pressed
into the service of orthodox theology and the Protestant revolt against
ecclesiastical authority. During the fourteenth and the fifteenth
centuries the resources of the Eastern Empire were ransacked for the
rhetoricians and sophists neglected by the empirical disposition of
Arabic scholarship. The political speculations of the ancients became
the rationale of Protestant democracy. As the influence of Platonism
on science succumbed to the success of the new experimental and
quantitative methods which were gaining ground in physics, classical
humanism completed the divorce of moral and natural philosophy by
elevating the authority of Plato in politics: but before classical
humanism had gained ascendancy in the mediæval universities, an
ascendancy which became a monopoly in the grammar schools, Arab science
had implanted in the oldest seats of European learning a seed destined
in the fullness of time to challenge not merely the authority of
church councils but the authority of print, to place the authority of
experience above the authority of the written word, as Protestantism
had placed the authority of the written word above the authority of
church councils.
Plato would have had little use for physicists in his Utopia. To outlaw
science was the last thing which Protestant rulers were prepared to do.
The great navigations had made science a necessity to the mercantile
interests. So long as they refrained from making themselves a nuisance,
like Servetus whose inability to envisage the Trinity in its correct
numerical proportions earned for him a harsher fate than that of
Galileo, scientists must be left alone. The world had outgrown the
Aristotelian compromise. The time had come to replace it by some new
device.
The Cartesian philosophy met the new situation by defining separate
spheres of autonomy for the scientist and the metaphysician. It did
not attempt to mix metaphysics and science in a uniform system of
nature. With his propositions and demonstrations “which establish the
existence of God and the distinction between the mind and body of man
disposed in geometrical order” Descartes stumbled upon the felicitous
notion that God ordained the investigation of nature according to
strictly mechanistic principles. “Now that I know him,” he discloses
in Meditation V, “I possess the means of acquiring a perfect knowledge
respecting innumerable matters, as well relative to God Himself and
other intellectual objects as to corporeal nature, in so far as it is
the object of pure mathematics.”
So piety prescribes that the scientist, contrary to the admonition
of Aristotle, must apply mathematics to the investigation of nature.
By the same process of reasoning or inspiration Descartes arrives at
the conclusion that teleological hypotheses in natural science are an
impious abrogation of the prerogatives of Deity. “Likewise finally,” he
asserts in the _Principles of Philosophy_, “we will not seek reasons
of natural things from the end which God or nature proposed to himself
in their creation (i.e. final causes), for we ought not to presume so
far as to think that we are sharers in the counsels of Deity, but,
considering him as the efficient cause of all things, let us endeavour
to discover by the natural light which he has planted in us, applied
to those of his attributes of which he has been willing we should have
some knowledge, what must be concluded regarding those effects we
perceive by our senses; bearing in mind however what has been already
said, that we must only confide in this natural light so long as
nothing contrary to its dictates is revealed by God himself.”
As Descartes was prepared to concede to mechanistic science the entire
brute creation, the Cartesian framework provided plenty of latitude
for biological investigation. Descartes stimulated experimental
physiology by his own ingenious speculations; and his influence on
physiology survived after it had been superseded by later philosophical
systems. In biology the Cartesian tradition has fallen into discredit
through the rise of evolutionary ideas. The evolutionists persisted in
following “the natural light;” and their theological contemporaries
maintained that it led them to conclusions contrary to what had been
“revealed by God Himself.” Since then biologists have been faced with
the alternative of pressing forward to a more radically mechanistic
conception of life, or abandoning it altogether. I have called the
extension of the mechanistic conception the _publicist standpoint_ in
contradistinction to _holism_, the most recent compromise.
In _Science and the Modern World_ Dr. Whitehead calls the period
immediately before the Renaissance the Age of Reason. That which
followed is the Age of Faith. The Age of Argument and the Age of
Confidence might perhaps describe the difference in more significant
terms. Confidence in the method of science has grown gradually with
the expansion of civilization. What is called modern science has
arisen, because innumerable, at first independent, lines of enquiry
have coalesced. It has not come into being because the men who have
pursued these separate but converging paths have had any general
theory about nature as a whole, purposeful or otherwise. Curiosity has
always induced some men to speculate without investigating, others to
investigate without speculating beyond their terms of reference, and
a good many to do both. Aristotle was neither the first nor the last
scientist to write a natural history and a volume of Gifford lectures.
Newton divided his time between gravitation and the prophecies of
Daniel. Faraday elaborated a theory of the ether and advocated
the tenets of Sandemanism. Aristotle’s natural history, Newton’s
gravitation and Faraday’s ether were not the philosophical complements
of their respective ethical, political or devotional beliefs. Aristotle
dissected animals, Newton gazed at the stars, Faraday experimented
with his electrical machine, because they were interested in living
creatures and the heavenly bodies and electrical phenomena.
The pursuit of science has its personal impulse in curiosity and its
social impulse in the power which science confers. The Greeks accepted
or rejected as illusory the evidence of their senses. In Aristotle’s
system science does not beg for a philosophical sanction. It was
reserved for the piety of Descartes to introduce the singular idea
that the scientist requires a licence to practice signed and stamped
by the metaphysician. The idea that science requires a metaphysical
justification has been revived by Dr. Whitehead who adopts a novel, and
I think incorrect, view of Hume’s contribution to philosophy. When the
scientist enters the field of contemporary philosophical controversy,
he is confronted with a jargon whose existence has very little
historical or logical connexion with the assumptions on which he works.
It is not surprising that he remains, in the words of Dr. Whitehead,
“blandly indifferent” to the arguments with which Hume refuted those
notions of causality and inference which traditional philosophers have
chosen to regard as the justification of science. The important fact
about Hume’s argument is that he refuted the pretensions of moral
philosophy by the same arguments which demolished the irrelevant dogmas
which natural philosophy inherited from the age of scholasticism.
Starting from a purely introspective basis Descartes attempts to find a
justification for the growing confidence of mankind in the testimony of
the senses. The subjective empiricism of Locke is still groping after
the same solution. Hume pursues this method to its bitter conclusion;
and shows that it led to complete scepticism. He proves to his own
satisfaction that the method of introspection cannot be made the basis
of socially communicable knowledge. The theory of a public world builds
upon that foundation, by examining the characteristics of questions
to which a socially communicable answer is possible. The strength of
Hume’s position is more apparent in our own generation than it was at
the time, when he wrote. Our expectation of living has increased as
we have learned to worry less about the good life and more about the
good drain. That the questions with which science deals are legitimate
objects of enquiry and that the method which science adopts is the most
satisfactory way of answering them is tacitly accepted by everybody who
avails himself of the amenities of a railway time table, the bioscope,
the telegraph office, the diphtheria vaccine, the ocean liner and the
air mail. If we do not attempt to answer the questions which perplexed
Socrates, it is because we have at our disposal a vastly greater body
of material to guide us in determining what characteristics of a
question make it suitable for being asked. We cannot say whether the
wise man will obey the laws, if he thinks that he will not be found
out; but we are less interested in knowing the answer, because we know
that it is highly probable that his finger prints will be traced.
Detective fiction has familiarized us with other devices which have
replaced the deathbed confession of the repentant atheist.
Hume applies the Cartesian method, demonstrates its sterility, and
arrives at this attitude which he states with no uncertain sound in a
passage which occurs at the conclusion of the essay on “The Sceptical
or Academical Philosophy.” “When we run over libraries persuaded of
their principles, what havoc must we make? If we take in our hand any
volume of divinity or school metaphysics for instance, let us ask, Does
it contain any abstract reasoning concerning quantity or number? No.
Does it contain any experimental reasoning concerning matter of fact
and existence? No. Commit it then to the flames. For it can contain
nothing but sophistry and illusion.”
In Hume’s scepticism natural science is no longer the man with the
muck rake, and metaphysics is no longer the divine science. Kant’s
critique now appears to salvage supernaturalism by a compromise in
which the Cartesian method is reversed, and a greater confidence in
scientific method is evident. He invokes science to save the soul
of man. Newton’s system had made space and time the basic concepts
of science. The physiology of Kant’s generation had not extended
its enquiries beyond the range of the five senses with which the
Greek empiricists were familiar. Kant seized upon this limitation of
eighteenth-century biology to substantiate the contention that science
draws upon information which is independent of sensual experience. In
Kant’s idealism space and time, the basic concepts of science, appear
as purely mental constructions. This was not a new point of view; but
the prominence it assumed was new, and resulted from the character of
contemporary science and the conclusions which Hume had advanced.
Volumes of speculation on the relation of time and space to sensual
experience have been written both by physicists and metaphysicians on
the assumption that the human frame possesses no means of recording
its own rhythms and its orientation to the earth’s gravitational
field. Mach is the only natural philosopher who has hinted at the
possibility that the Kantian argument might be re-examined from the
modern biological standpoint. Modern physiology is not circumscribed
like the physiology of Kant by the five senses. It recognizes ten or
eleven distinct types of receptor elements in the human body. Two
of these are immensely significant to the attitude which we adopt
to Kant’s criticism of Hume’s position. In 1828 the experiments of
Flourens first demonstrated that animals are receptive to the influence
of gravity. The receptive area in our own bodies is located in that
part of the internal ear, sometimes called the labyrinthine organ. Just
as removal of the eye prevents a fish from responding to its background
by colour change, destruction of the labyrinthine organs abolishes its
characteristic orientation in space, when swimming. We do not say that
a cat falls on all fours, because it has a priori knowledge of space
relations. It falls on all fours, because the orientation of its body
as a whole is recorded by its labyrinthine organ, and the appropriate
muscles are brought into play by reflex action. The possibility that
orientation of individual members with reference to one another might
be regulated by a self-recording arrangement is a comparatively recent
discovery. Sherrington has shown that the tendons and muscles possess
special structures which he calls proprioceptors. They respond to the
stretching of the muscles. By virtue of those muscular rhythms which
Galileo employed as his standard of reference in devising the first
clock, the human body is itself a self-recording timepiece. Pavlov does
not appeal to a priori knowledge of time to interpret the interval
which elapses between the ringing of a bell and the secretion of saliva
in a dog.
The belated discovery of the labyrinthine organ and the proprioceptors
is easy to understand. We live in a world in which day and night follow
one another. We can close our eyes and darken our vision. The eyes are
exposed to view. Their connexion with light calls for no elaborate
demonstration. The labyrinthine organ and the proprioceptors are only
accessible to dissection or to the microscope. We can never get away
from the influence of gravity or the rhythms of our own bodies. What we
never miss, we fail to notice. This peculiarity of our corporeal nature
gives a peculiar and fallacious plausibility to Kant’s contention
that we can take away from a body its colour, weight or smell, all of
which can be “referred to mere sensuous experience,” while “the space
which it occupied still remains and this is utterly impossible to
annihilate in thought.” To annihilate space is not an impossible feat
of imagination for the modern biologist. In Rupert Brooke’s poem the
heaven of fishes harbours the worm that never dies. If the metaphor
had been pushed a little further, it would have transpired that the
philosophy of fishes might well contain many axioms that are omitted
in the Kantian critique. Fishes in general have no eyelids. They can
be kept in a uniformly illuminated aquarium without the experience of
darkness. The sharks and their allies possess a small duct by which
the internal ear communicates with the exterior. It would not be an
impossible operation to remove and replace the contents of their
labyrinthine organs, and render them temporarily indifferent to the
earth’s gravitational field. A philosophical fish confined from birth
to a uniformly illuminated aquarium and subjected from time to time to
this simple operation, might conceivably invert the Kantian argument.
He would be shocked by the gross materialism of an undulatory theory of
light; but he would be willing to be convinced about any quaint views
upon space which the piscine physicists propounded.
§3
Kant’s doctrine that space and time are concepts necessarily
independent of one another and of sensory experience has only come into
conflict with the fruits of scientific enquiry in our own generation.
In spite of this the influence of Hume has steadily increased and
the influence of Kant has declined during the intervening period.
Psychology, brought into existence by Kant’s appeal for a science which
would define the characteristics of a priori knowledge, has betrayed
its parent. In every department of human enquiry investigators are
asking, does it contain any abstract reasoning concerning quantity or
number, does it contain any experimental reasoning concerning matter
of fact or experience? Mr. Bertrand Russell, an impenitent advocate
of a priori knowledge in his capacity as a mathematician and an
uncompromising empiricist in his capacity as an educationist, tells
us that “logic must no more admit a unicorn than can zoology, for
logic is concerned with the real world just as truly as zoology.” Dr.
MacDougall, the most vigorous contemporary critic of the behaviourist
standpoint, is devoting his energies to the breeding of genetically
pure stocks of Wistar Institute white rats. A professor of political
science in London University so far departs from the traditions of
his discipline as to collect statistics on the number of hours which
members of Parliament actually devote to their democratic activities.
It was said by an old Scots balladmonger, “I care not who makes the
nation’s laws, while I sing her songs.” When the modern descendant of
Democritus is assured that materialism is on the decline, he may well
reply in a similar vein. We all behave as if we were behaviourists
nowadays.
Between Hume and Darwin, Adam Smith, Malthus, Quételet and Marx sowed
the seeds of the behaviourist standpoint in the soil of the humanities.
Darwin’s _Descent of Man_ precipitated a new phase in the revolution
which was replacing classical humanism by a humanism which draws its
inspiration from the success of natural science and looks to the
scientist to supply it with the first principles of method. It was no
longer possible to challenge the claim of science to the study of the
brute creation. The recognition of man as a by-product of the same
secular agencies undermined the last defence of the metaphysician.
Hegelian philosophy was a forlorn and belated attempt to lock the
stable doors after the horses had long since escaped. The piety of
Descartes had conceded that animals are automata. The brutal candour
of Darwin emphasized in a new light the fact that man is an animal. It
was fitting that William James should arise in the fullness of time to
proclaim the new gospel that philosophers are also men. If the full
force of this devastating sequence was not apparent to the pragmatic
apologists of the Pelagian heresy, it has acquired a new, and, I
believe, epochal significance through the breakdown of the Cartesian
distinction between reflex and voluntary activity in modern physiology.
To-day the influence of Hume’s empiricism and Darwin’s doctrine of
descent can be seen in every branch of social enquiry. In history
the materialistic bias is evident in the writings of those who would
be least willing to commit themselves to economic determinism as a
general hypothesis of social development. Economics has completely
severed its moorings to moral philosophy, and proudly boasts that
it is an ethically neutral science. The genetic aspect of human
behaviour is recognized in new endowments to encourage the pursuit of
social biology. If social psychology has hitherto remained immune
to the influence of modern research on animal behaviour, it borrowed
its equipment of instincts from the discredited speculations of the
selectionists. The humanities have passed out of the hands of the
grammarians in the higher seats of learning. Before another generation
has passed the accomplished fact will be officially sanctioned in the
earlier stages of education.
In its long apprenticeship to theological dogma classical humanism
has created a type of philosophy which is inimical to the temper
of scientific enquiry. This tradition has been perpetuated in our
educational system by associating the study of history and human
affairs in general with an exclusively linguistic rather than with a
scientific training in early life. The belief that philosophy lies
outside the province of science and that logic is more fundamental than
science has been so thoroughly inculcated by the classical tradition
that most men of science accept it with servile complacency. It is not
surprising that many of them view with alarm the magnitude of the new
territories which scientific method has incorporated within its domain.
In every period the birth of a new tradition has made the forces of
reaction more stubborn. This fact must be accepted. It is unwise to
expect results of far-reaching importance in social science in the
immediate future. If astronomy is the most exact of the observational
sciences, it is also the oldest. It began in Babylon and Egypt about
six thousand years ago. Economists and eugenists who hope to outgrow
their phlogiston theories in one generation take an unduly hopeful view
of the rapidity of scientific progress. New forms of compromise will
come to the rescue of custom thought and power thought, before social
science is able to replace the wrong way of asking a question by the
right way.
It is highly probable that the next century will witness a
consolidation of supernaturalistic tendencies in western Europe. It
is legitimate to entertain the possibility that the rival attitude,
reinvigorated by fresh triumphs of scientific method in the treatment
of human affairs, will revive with greater vitality, if not in our
own civilization, in that which takes its place. I am in complete
agreement with Dr. Haldane, General Smuts, Professor Eddington and
Dr. Whitehead, when they assure us that the materialistic tendency
in philosophy, which was gaining ground under Darwin’s influence, is
less popular to-day. I venture to interpret the reaction in a way
with which they would not agree, and to believe that it has retreated
_pour mieux sauter_. The mid-nineteenth century in Great Britain was
a period of prosperity and expansion. In Huxley’s generation unbelief
was the luxury of a privileged class which was not afraid of the man
in the street. The period in which we live is one of ferment and
disintegration. In its impetuosity to settle the problems of human
conduct, it will not be content to await the slow advance of science.
Mechanistic philosophy cannot offer to the privileged a supernatural
sanction for the things they value most. It cannot proffer to the
unprivileged the shadowy compensation of a world into which the
thought of science is unable to penetrate. A mechanistic philosophy
might conceivably be popular in a society in which gross inequalities
of possession did not exist. To-day it can only flourish among those
who have leisure to study, when their privileges are not compromised
by social unrest. He who has the temerity to defend the mechanistic
position need not expect any laurels from his own generation. He
cannot seek sanctuary in the fearless candour of a contemporary Huxley
or a contemporary Tyndall. He must extract what comfort he can glean
by reflecting that the system of Aristotle triumphed over that of
Epicurus, and the thought of the nineteenth century was nearer to
Epicurus than to Aristotle. Scanning the new blossoms which have lately
been added to the nosegay of philosophic compromise, he will say with
Swinburne,
“But for me their new device is barren, the times are bare,
Things long past over suffice, and men forgotten that were.”
X. PUBLICITY, REALITY, AND RELIGION
“Conscientiousness in small things, the self-control of the
religious man, was a preparatory school for the scientific
character, as was also, in a very pre-eminent sense, the attitude
of mind which makes a man take problems seriously, irrespective of
what personal advantage he may derive from them.”--Nietzsche, _The
Will to Power_.
§1
Whatever may be said against pragmatism, it served a useful purpose
in calling attention to the connexion between people’s temperaments
and their philosophies. William James classified philosophers in
two genera, the tender-minded and the tough-minded. I believe that
there exists a more fundamental distinction between two types which
correspond to the introvert and the extrovert of the psychiatrist.
Our attitude to the scope of philosophy is determined by whether
we take an individualistic or a social view of what constitutes
truth. In the one case our canons of logic will be inferred from an
examination of the properties of propositions which carry conviction
to ourselves individually, in the other by an examination of the
properties of propositions which are best equipped to obtain general
assent. For this reason I am not convinced that Bertrand Russell
is right in thinking that modern logic brings the most devastating
criticism to bear on traditional philosophy. Modern logic has not
been devised with the aim of achieving the same results as those
which constitute the goal of traditional philosophers. It is not
surprising that traditional philosophers, finding its conclusions
unpalatable, remain unconverted. Modern logic is the offspring of
mathematics, and mathematics has developed in intimate association
with science. For the last seven hundred years traditional logic and
introspective philosophy have been no less intimately associated with
theology. Hence has arisen the arrogant assumption that on account of
its subject matter introspective philosophy is more fundamental than
science. There is no reason why we should regard it in this light.
If philosophy is knowledge, it is presumably something transmissible
by discourse. Otherwise it is difficult to formulate any distinction
between knowledge and mere opinion or superstition. We cannot therefore
discuss knowledge without taking into account the people who share
it. The most important characteristic of scientific beliefs is
their communicability. Those who take the social as opposed to the
individualistic attitude to truth will embark on their adventures by
examining the characteristics of scientific judgment. To any one who
is not an incorrigible individualist the results of scientific enquiry
must establish the anatomy of philosophy. Whether I am by temperament
an individualist or otherwise I am forced to submit to the discipline
of discourse in practice. Let us suppose that two individuals N and
M are engaged in public discourse concerning the Nature of Life. N
states the proposition “I (N) am a conscious being.” M states “I (M)
am a conscious being.” The only neutral ground for the discussion of
the two statements is the more general statement “N and M are conscious
beings.” In the nomenclature suggested elsewhere in these essays this
neutral ground is the resultant of the public components of the two
original statements which N and M make. Personal statements may be
looked upon as complex variables. Philosophy is the technique of
operating with the real (public) part of such statements and separating
them from the imaginary (i.e. private) part. This distinction is not
abolished by the fact that the temperaments of some philosophers lead
them to apply the term _real_ to the private and _imaginary_ to the
public component. The fact remains that in public discourse we have
to operate with the public component. The public statement “N and M
are conscious beings” implies our ability to define characteristics of
behaviour which are denoted by the adjective _conscious_. This task
which now lies within the scope of biological investigation refines
the publicity in the concept of consciousness. For the performance of
public discussion the term “_I_” is a member of the class denoted by
“_Man_.” Anything implied in public discussion by the statement “I am
conscious, etc.,” is included in the statement “Man is a conscious
animal.” The significance of anything which cannot be subjected to this
limitation is a purely _private_ matter. From this it follows that a
discussion of the Nature of Life is complete, when we have taken into
account the characteristics of conscious behaviour. On the contrary
view the propositions of philosophy are not necessarily communicable.
The theory of a _public world_ suggested in a previous essay on the
Nature of Life corresponds very closely with the attitude adopted by
Poincaré in the following passage which occurs in his _Foundations of
Science_:
“Sensations are therefore intransmissible or rather all that is
pure quality in them is intransmissible and forever impenetrable.
But it is not the same with relations between these sensations.
From this point of view all that is objective is devoid of all
quality and is pure relation.... Nothing therefore will have
objective value except what is transmissible by discourse...”
So far as it goes there is nothing essentially new in this statement.
It represents an attitude common among thoughtful people with a
scientific training. Professor Eddington is in agreement with it when
he writes:
“For reasons which are generally admitted, though I should not
like to have to prove that they are conclusive, I grant your
consciousness equal status with my own; and I use this second-hand
part of my consciousness to ‘put myself in your place.’ Accordingly
my subject of study becomes differentiated into the contents of
many consciousnesses, each constituting a _view-point_. There then
arises the problem of combining the view-points, and it is through
this that the external world of physics arises. Much that is in any
one consciousness is individual, much is apparently alterable by
volition; but there is a stable element which is common to other
consciousness. That common element we desire to study to describe
as fully and accurately as possible, and to discover the laws by
which it combines now with one view point, now with another. This
common element cannot be placed in one man’s consciousness rather
than in another’s; it must be in neutral ground--an external
world... The external world of physics is thus a symposium of the
worlds presented to different view-points...” (p. 283, _The Nature
of the Physical World_).
How then does it come about that “a universal Mind or Logos would
be, I think, a fairly plausible inference from the present state
of scientific theory”? (p. 338). Or again, how are we to draw the
conclusion “from those arguments from modern science that religion
first became possible for a reasonable scientific man about the year
1927”? I think that we may possibly find an answer to these questions
by bearing in mind that Professor Eddington’s external world is the
external world of physics rather than the public world of physics plus
biology. Throughout his exposition he assumes that biologists are still
committed to the dualistic standpoint of the Cartesian tradition. Thus
he states: “a mental decision to turn right or turn left starts one
of two alternative sets of impulses along the nerves to the feet. At
some brain centre the cause of behaviour of certain atoms or elements
of the physical world is directly determined for them by the mental
decision...” (p. 312). It is not clear why there is in what Professor
Eddington calls the “mystical experiences” of different people
sufficient “neutral ground” to provide the basis of a symposium with
as universal a sanction as that of the external world of physics. That
after all is implicit in our notion of religion. It is not difficult
to see why he finds no objection to placing his external world under
the direction of a universal mind, since he assumes that the teleology,
which has been abandoned in dealing with non-living matter, is quite
indispensable in dealing with living matter.
It must be admitted that Professor Eddington could claim the support
of at least one eminent biologist who holds that the method of the
biologist is different from the method of the physicist, and the
method of the physicist can never be applied to the analysis of
“conscious behaviour.” However stoutly Dr. Haldane may advocate the
first proposition his many distinguished contributions to biological
science are little calculated to illustrate its truth. He has made
important additions to our knowledge of the physical chemistry of the
blood by adopting the method of the physicist. When, if ever, he has
departed from that method he has done so without the assent of his
fellow physiologists. The practice of even the most exemplary persons
not infrequently falls short of the loftiness of their professions,
and it is perhaps unfair to criticize Dr. Haldane on this account.
The weakness of Dr. Haldane’s philosophical position resides in the
fact that he gives no consideration to the new issues raised by the
physiology of the conditioned reflex. Pavlov’s work has shown us that
even when he is dealing with “conscious behaviour,” the biologist
can still approach the subject matter of his enquiries with the same
attitude which the physicist adopts.
On the whole people are more interested in conscious behaviour than in
anything else. Before science could attempt to tell us something about
conscious behaviour, Poincaré’s outlook could never have a far-reaching
appeal. The history of human thought again and again proves that people
will always fall back on the language of magic, when the language of
science provides them with no vocabulary in which to discuss the things
that interest them most. Magical views of the world have declined not
because science disproves them, but because science provides better
ways of discussing the same issues. If we can usefully treat the
characteristics of conscious behaviour without invoking a holistic
or animistic concept of consciousness, the scope of introspective
philosophy must in time dwindle to a vanishing point. Philosophy will
then confine itself to examining the logical structure of scientific
theories. It may seem more natural, more in keeping with common sense,
to think of a wholeness defined by the term consciousness than to face
the tremendous intellectual effort of envisaging the behaviour of an
organism from an atomistic standpoint. If the latter contains within
it the capacity of growth and of yielding verifiable conclusions which
cannot be derived from the traditional point of view, consciousness
must go as gravitation and action at a distance must go, however much
Kant and common sense may urge the _a priori_ necessity of a Euclidean
space and a measure of time that is independent of it. As scientific
investigation invades the domain of conscious behaviour the way will be
open for developing a new outlook in philosophy, one that is neither
intrinsically monistic nor intrinsically pluralistic, since it makes no
such claims to finality as the academic philosophies of the past have
usually done.
§2
Professor Eddington, like Professor Whitehead, entertains the hope
that science may eventually lead us to conclusions about the universe
involving something more than practical utility on the one hand and
mere intellectual satisfaction on the other. The reasons which they
give are not sufficiently definite to criticize, as they would perhaps
themselves admit. It is more easy to understand the point of view of
Mr. Sullivan, an impenitent individualist, who is frankly resentful
towards science, because science cannot serve the needs of theology or
provide sanctions for his æsthetic predilections.
“The greater importance that men attach to art and religion,” he
maintains, “is not due simply to their ignorance of science. Art
and Religion satisfy deeper needs; the problems they deal with
are intrinsically more important.... Our æsthetic and religious
experiences need not lose the significance they appear to have
merely because they are not taken into account in the scientific
scheme....”[8]
The real significance of these remarks would be much clearer, if Mr.
Sullivan had substituted the word _personally_ for _intrinsically_.
Mr. Sullivan is by temperament an individualist philosopher. For him
what is _true_ has a specially personal value. Scientific beliefs are
only _convenient_. Thus in discussing the system of Copernicus he
makes the comment, “it was convenient; the question of whether it was
true or untrue was not explicitly discussed.”[9] Consistently with the
individualistic standpoint in philosophy Mr. Sullivan does not divulge
the inward revelation which empowers him to distinguish with such
nicety between propositions that are “true” and propositions that are
merely “convenient.”
It sounds very impressive to state that science leaves out of account
man’s religious and artistic experiences, that religion and art satisfy
deeper cravings and so forth; but religion and art are two words which
are rarely used by any two people in the same sense or by any one
person in the same sense on two successive occasions. Which religion
does Mr. Sullivan mean? Is he a Buddhist, a Seventh Day Adventist,
a Shintoist, or a Bahai? Is his religion an ethic or a cosmogony,
or both? Until he has defined his position more explicitly, it is
difficult to be quite sure what he is talking about. The terms art and
religion are used in very different senses. That being so, to say that
everybody has religious or æsthetic experiences does not necessarily
imply the existence of any common plane of thoughtful intercourse
other than the conceptual world of science. An expert social hostess
recognizes this when she wisely refrains from asking Mr. A who is
interested in Art to meet Mr. B who is interested in Art.
In seeking to transcendentalize his private world, Mr. Sullivan
has not been altogether felicitous in coupling together Art and
Religion. Although many people become very irritable in the course of
a discussion on the merits of vorticism or free verse, most educated
persons admit on reflection that such discussions owe their interest to
the light they shed on differences of temperament in the disputants.
It is true that professors of literature in Universities and rather
youthful reviewers sometimes take a more pontifical view of their
own powers of divination, but even our schools have got beyond the
stage, when it was thought proper that children should be whipped into
believing that Wordsworth’s _Idiot Boy_ is a _great_ poem. Whether Mr.
Sullivan chooses to say that Van der Waal’s equation is true or merely
convenient, it may be suggested that he would embark on a discussion of
its truth or convenience with some hope of final agreement. I believe
that Mr. Sullivan would embark upon an argument about a question of
æsthetics with much less hope of changing his opponent’s attitude than
if he were discussing Van der Waal’s equation. Mr. Sullivan has no
need to appeal for a transcendental sanction for æsthetic experience.
Æsthetics are questions about which sophisticated people agree to
differ.
With religion it is different. Whereas a person can have very genuine
artistic interests without claiming a universal, transcendental or
_public_ sanction for his own preferences, religion ceases to be
religion and becomes æsthetics or ethics, when it does not put forward
such claims. A consideration of the following illustration will make
this clear. A derives satisfaction from reciting Mr. Yeats’ poem, “The
faeries dance in a place apart...” etc. B derives satisfaction from
singing the evangelical hymn that contains the lines “Bright crowns
there are, bright crowns laid up on high...” Inasmuch as the first form
of satisfaction involves neither belief nor unbelief, it is properly
described as artistic or _æsthetic_. Inasmuch as the second implies
in addition the conviction that a certain ponderable object exists at
a certain height from the earth’s surface, as in the cruder forms
of evangelism it does, the satisfaction derived from singing it is
_religious_.
The word religious is used in so many different senses that it is
dangerous to employ it at all without examining it more closely.
Cynical paradox-mongers not infrequently complain that materialists
are “religious.” When so used, the term merely implies a sense of the
importance of belief. In an unscientific age persons of this type
would probably gravitate towards some form of religious organization.
Looking at religious organizations as a whole one sees two sharply
contrasted components in the majority: views about human conduct or
the ethical aspect of religion and views about the nature of the
universe or cosmogony. To-day, most educated people regard the latter
as the proper sphere of science. We are told by modernists that the
earlier chapters of the Book of Genesis are to be cherished for the
sublime ethical teaching they impart. What sublime ethical teaching
is implied in the prohibition to eat of the fruit of the tree of
Knowledge or in the story that woman was manufactured from a man’s rib
as an afterthought of creation need not detain us. It is only partly
true to say that liberal theologians have surrendered the sphere of
cosmogony to science. They have surrendered the details, but they have
not surrendered the prerogative of imposing upon whatever cosmogony
the scientists supply a teleology of their own. This teleology is, it
is true, so attenuated as to embarrass the advance of science far less
than those more crude revivals of animism sometimes inappropriately
classified under the generic heading New Thought. Its justification
becomes less and less calculated to carry conviction, as the domain of
scientific method is officially sanctioned by the Churches. The advance
of scientific knowledge reinforces the suspicion that an attitude to
experience which leads to misleading or sterile conclusions about the
details of our cosmogony can hardly be expected to prove essential to
the finished picture.
Just as the cosmological aspect of religion has become resolved into a
_public_ component which has passed over into the province of science
and a personal component for which the mystic seeks to formulate
some ulterior transcendental sanction, the ethical side of religion
consists of values which must be taken or left and prohibitions or
admonitions which can be rationally discussed as instruments for
promoting the acceptance of these values, if the latter are taken for
granted. Here again the claims of liberal theologians become more
modest with the advance of more complex methods of social organization.
Sunday observance, fasting, prohibitions against dancing, smoking and
theatricals become less and less fashionable. Even in the domain of
sex, where animistic views of human conduct are more obtrusive, we
find that Anglican deans are making the entertaining discovery that
birth control is fully compatible with the teachings of Christianity.
Most Christians will agree that war is contrary to the “spirit of
Christ’s teachings.” When a war happens to be in progress, they give no
objective evidence that this conviction differentiates their conduct in
any way from that of people who are not in the least interested in the
spirit of Christ’s teaching. An exception might here be made in favour
of the Quakers. The Society of Friends, the only religious body which
engaged the respect of Voltaire, have shown so little disposition to
proselytize that they are hardly to be looked on as a religious body.
They might with equal propriety be called an organization of persons
interested in the art of living. Significantly enough they do not call
themselves a Church.
In practice the hard and fast ethical claims of religious leaders
tend with the advancement of civilization to become less pretentious.
The details of regulating human conduct have been conceded to the
politician and the educationist, just as cosmogony has been surrendered
to the scientist. Religious organizations cling tenaciously to some
obscure transcendental sanction for the fundamental assumptions on
which the politician or educationist is expected to work, assumptions
which, as earlier remarked, seem in actual practice curiously
irrelevant to the behaviour of their devotees. The increasing vagueness
which surrounds the nature of “revelation” in the teachings of Liberal
Churchmen renders the task of making this sanction communicable one
of overwhelming difficulty. In relation to human conduct there is
obviously a large domain of questions on which rational discourse is
possible, in so far as the fundamental assumptions are agreed upon
by all parties. In this sense ethics belongs to the public world and
ethics and politics are the same thing. There still remain private
differences with regard to the premises. The Roundheads realized that
transcendental ethics cannot be made the subject of argument. They
acted intelligibly on the assumption that the only answer to the Divine
Right of Kings was to make a spectacle of the head of Charles Stuart to
Gods and men.
When Professor Eddington employs the term mystical experience
indifferently for æsthetic and religious sentiments, he is perfectly
justified in so far as the ultimate constituents of religion, those
residues of religious belief which have survived the secularization
of social life and the advancement of scientific knowledge, belong
to the private worlds. From a purely individualistic standpoint the
“religious” satisfaction that the Liberal theologian derives from the
crude teleology of the Chaldæan mythos is difficult to distinguish from
the artistic satisfaction sought by others in the vague teleology of
Wordsworth’s _Tintern Abbey_. Regarded from a social angle there is a
profound difference between the religious and the artistic experience.
Because of that difference Professor Eddington’s conclusion that there
is nothing in the outcome of scientific enquiry to prevent a reasonable
man from entertaining religious beliefs is a profoundly misleading one.
When Professor Eddington speaks of religious experience he clearly
means something which belongs to himself privately. When the vast
majority of people speak of religion, they mean a body of beliefs which
can be transmitted through the medium of discourse like scientific
beliefs. Far from being regarded like artistic preferences as a private
affair of the individual, such beliefs are promoted by exceedingly
powerful organizations which still exercise an immense effect on social
behaviour. This influence takes the form of interference on the part of
the Churches in every attempt to encourage birth control, to promote
true information about sex among the young or to humanize the divorce
laws. The scientific philosopher is entitled to his own private mythos
with which no sensible people would wish to interfere, provided that
he does not pester his fellows with it. It is still permissible to ask
whether he is justified in employing language in such an equivocal
manner that his words will be used, when he must know they will be
used, to give all the weight of a distinguished reputation to those
forces of social organization which in the past have exercised a
constant restraint on the freedom of scientific enquiry and do at
present exert a tremendous influence upon the shaping of human conduct.
That the distinction we have drawn above between the religious and
the æsthetic is the significant one for the purpose of ordinary
usage is easily seen by considering the dislike that some people
entertain for pork. In a Gentile this is an æsthetic attitude. In the
Jew it is a religious one. The thesis that artistic values, or more
generally what Professor Eddington calls the mystical experience,
belong to the private world requires an important qualification. It
does not imply that Art cannot be made the subject of discussion. A
mechanistic philosophical outlook is often stigmatized on account of
its supposed dullness, and shunned because it seems to leave no place
for after-dinner conversation. This is not so. The mechanistic outlook
does not imply the end of æsthetic criticism. It merely insists that
such criticism shall conform to the standards of the public world.
There is abundance of fascinating problems dealing with the orientation
of human interest to particular objects which come within the scope
of æsthetic criticism. The theory of a public world which has been
developed elsewhere leaves open the possibility that we may one day
have genuinely scientific knowledge about these things. If that day
comes, we shall be able to argue about art and ethics without losing
our tempers. As the behaviouristic standpoint encroaches on the field
of art criticism, it is probable that the nice distinction between
those matters of taste which we call æsthetic values and those which we
call ethical sanctions will seem more arbitrary than the advocates of
Art for Art’s sake postulate.
The conflict between religion and science tends to be obscured by the
circumstance that the official apologists of the former, if they are
well-educated persons, state their case in such a way as to convey
the impression that they only claim that their view of human destiny
is a permissible one. This does not alter the fact that religious
leaders both of the right and left wing _behave_ on the assumption
that their views have a universal sanction. In very few parts of the
English-speaking world is it possible for a child to go to school
without being taught the tenets of some religious body. One does not
notice that Liberal theologians who state their case on the frankly
private basis of mystical experience are much more sympathetic than
Fundamentalists to the legitimate claims of the agnostic parent who
wishes his child to have a secular education. The term religion cannot
be detached in its objective, or in the terminology of these essays its
_public_, aspect from _organization_. Professor Eddington has justified
his right to a “mystical experience.” He has not proved his claim to
have a _religion_ as the average parent understands that term. If the
scientist uses the term _religion_ for something different, knowing
that his words will be used by religious leaders to reinforce their
claims to a universal sanction for their own “mystical experiences,”
the secularist parent may legitimately feel that the scientist is not
giving him a square deal as a fellow citizen.
§3
We must attribute to its long association with theology the idea that
philosophy deals with something mysteriously called _Reality_, lying
outside the secular province of science. The term Reality has acquired
the value of magical gesture in academic philosophy. Its everyday
use as a measure of the intensity of one’s conviction throws a good
deal of light on what is meant when it is used to define the goal
of philosophy. To the introvert the private world is most _real_. To
those who have a more socialized attitude to experience the public
world of science is most _real_. The fundamental difference that
exists between the introvert and the extrovert type of philosophy
is not abolished by introducing the word reality into the language.
It is partly because the term “external world” has been used with
more emphasis on its “reality” than on its communicability that I
have preferred to speak of a _public world_. The classification of
different experiences as external or internal is less important than
the recognition that some are communicable and others less so. In
this nomenclature scientific beliefs are distinguished especially by
their _publicity_. The fundamental distinction between the domain of
intellectual public enterprise and intellectual private enterprise
is just as valid, whether we approach the question from the frankly
solipsistic standpoint adopted by Professor Eddington on p. 268 of his
Gifford Lectures or the equally explicit objective idealism of p. 272
of the same work.
In my undergraduate days there was a legend of an eminent philosopher
and a Fellow of Trinity. Returning to his room in the early hours
of the morning after a liberal potation of audit ale, he lay down
upon the hearth-rug, covering himself with one of the large shallow
footbaths which were still used by all classes of academic society.
When his bedmaker arrived a little later, he explained that he was an
oyster, and raised objections to any one tampering with his shell.
I do not know whether the story is true, or whether the philosopher
was a solipsist. I presume that in the course of the same day, he
realized that his experience of the footbath had a more extended
significance than his experience of the oyster shell. If he were a
solipsist and decided to remain such after the incident in question,
he was presumably forced to recognize from Audit eve onwards, that
certain ingredients of his consciousness had a more permanent
status than others. If human beings exist only in my own individual
“consciousness,” they constitute necessary points of reference in
classifying other types of experience. The distinction between
_the_ public world and _my_ private world does not uniquely owe its
usefulness or significance to any assumption concerning the existence
of a reality external to my own consciousness. The important feature
about the world construction of science is not its externality but its
communicability. Communicability remains a perfectly definite basis
for the classification of beliefs, even if I choose to deny that other
human beings have an independent existence.
In secret the individualist is entitled to cherish the belief that his
own private world is more “real” than the public world of science. One
suspects that Mr. Sullivan does so. Professor Eddington is evidently
worried because he finds himself doing so. Under the influence of
love or alcohol we have all been solipsists at some time or other. As
Professor Eddington has lucidly stated in a passage quoted earlier in
this essay, so soon as we engage in public discourse we are compelled
to seek for a neutral ground. We agree to leave our private world
behind. To make discourse possible we accept the neutral ground as
the real thing. This neutral ground is the public world of science.
The idea that philosophy is more fundamental than science has arisen
through the absent-mindedness of philosophers. This permits them
to overlook the fact that there cannot be philosophy unless there
are philosophers. As soon as more than one individual begins to
philosophize the search for a neutral ground becomes a necessity of
social intercourse. From a social point of view the neutral ground is
the only thing which can be spoken of as real. Although philosophers
often try to give the impression that human beings exist in virtue
of the fact that there is such a thing as philosophy, it is more
sensible to hold that philosophy exists in virtue of the fact that
there are human beings. Because philosophers are themselves members
of human society, the proper goal of philosophy must be the search
for propositions that have the property of _publicity_ or socialized
reality.
The recognition of this restores to philosophy an intelligible
objective. From the point of view of the average person the philosopher
is “a blind man in a dark room chasing a black cat that isn’t there.”
The contempt of the plain man is partly justifiable, not because
the plain man is entitled to a plain answer to every question he
propounds, not because philosophers are blind, but because it is
waste of time to chase the cat, if there is really no cat to chase.
Traditional philosophy wedded to dogmatic theology has always assumed
that the cat is there to chase. Of late years the cat of traditional
philosophy, like the cat of _Alice in Wonderland_, has been gradually
disappearing. For the purpose of apologetics there is little left
of it but its smile. There have been philosophers who have been
content to admit their blindness and refrain from putting forward
any project to bell the cat. Of such was David Hume. It is now a
hundred and fifty years since Hume was buried. This may be why he is
recognized as an authentic philosopher. Those whose studies lead them
to entertain views somewhat similar to those of Hume are more usually
called anthropologists, physicists, physiologists, economists or
generically experts, while they remain alive. The grudging benediction
accorded to Hume’s remains by traditional philosophers is not wholly
due to a conventional respect for those who have departed. Hume
divested natural philosophy of some of the pretensions which it had
imbibed from its association with scholasticism. Philosophers with
an anti-scientific bias have chosen to regard this as an affront to
science. The scientist looking back over a century and a half of
unparalleled progress has no need to regard it as such. On the other
hand the scope of “moral” philosophy has dwindled since Hume’s time.
Psychology, until our own generation a branch of moral philosophy, is
clamouring to be recognized as a science. Anthropology has undertaken
the task of elucidating by painstaking observation those aspects of
human behaviour which are _publicly_ connected with what Professor
Eddington _privately_ speaks of as the “mystical experiences.” It may
be true that scientists in our generation are less outspoken than
Huxley and Tyndall in their criticism of traditional philosophy. It
may be true that those scientists who enter the field of philosophical
discussion often do so with the aim of reinforcing the beleaguered
battalions of the apologists of dogma. It is doubtful whether there was
ever a time in the history of western Europe when a secular outlook was
more widespread, and when the hope of finding a rational basis for a
universal religion was less forlorn.
When philosophers speak of a rational basis for scientific belief, they
seem to imply that the word rational can only signify that which is
evident independently of experience. It is profoundly doubtful whether
we can form any judgment about such a question. If it is possible to
arrive at a decision of this kind, I suspect that the solution will
come from those who study the behaviour of infants and the history of
science. There seems to be little hope of obtaining a solution from
introspective philosophers. In the meantime science will continue to
progress, whether the belief that relations between experience can be
ascertained is a rational one or is itself an outcome of experience,
whether the public world is the actual world or a shadow world,
whether the conclusions of science appeal to common sense or seem more
incredible than fairy tales. In a machine-made civilization however
unpalatable to common sense the conclusions of science may prove, the
future of science is assured.
In the philosophy of Hume we find the pragmatic justification of
science first stated explicitly. “To philosophize,” according to Hume,
“is nothing essentially different from reasoning on common life.”
Kant’s anxiety to give scientific enquiry a “rational” sanction was
based on the frank recognition that Hume’s scepticism threatened the
future of moral philosophy more than the future of science. Yet Kant
himself could not escape from the pragmatic criterion of publicity,
in asserting the superiority of his own system to that of Plato, who
“abandoning the world of sense, because of the narrow limits it sets to
the understanding... did not reflect that he made no real progress by
all his efforts, for he met with no resistance which might serve him
for a support, as it were, whereon to rest, and on which he might apply
his powers.”
In accepting Hume’s critique of traditional rationalism and attempting
to reinstate moral philosophy on the same footing of social convenience
as natural science, the modern pragmatists have proved more than they
intended. By insisting on the temperamental basis of philosophical
belief, pragmatism has robbed moral philosophy of all claim to
universality; and implicitly relegated it to the status of an art.
James believed that the doctrine of immortality is a physiological
necessity for some people. For others it is evidently not. Some people
anticipate with gratification an eternity of hymn singing. Others
shudder at the fate of the Struldbrugs. Both those who do find it
necessary to believe in immortality, and those who do not, live to-day
as citizens of a society whose amenities are the fruit of scientific
knowledge. In a machine-made civilization the amenities provided by
science are a necessity to every one. It is necessary to live in order
to philosophize. When the philosopher has finished all that he has to
say about the Nature of Life, it is the biologist who is called in by
his relatives to certify that he is legally dead. The universality
of science transcends in a very practical sense those differences of
temperament which determine the predilections of moral philosophers.
Scientific hypothesis makes social activity possible.
XI. PRIVACY, PUBLICITY, AND EDUCATION
“Nothing does more harm in unnerving men for their duties in the
present, than the attention devoted to the points of excellence
in the past as compared with the average failure of the present
day.”--Whitehead, _Science and the Modern World_
§1
Two conclusions, it seems to me, can now be drawn from the progress of
science. One is that, since we can never know everything we should like
to know, every individual has a right to his own private world. The
other is that there is no excuse for the sophisticated person refusing
to recognize where his private world ends and the domain of social
knowledge or the public world begins. From the first it follows that
there is no necessary antagonism between the claims of science and art
in a modern theory of education. From the second it follows that true
education is necessarily secular. It is generally agreed that education
includes something more than vocational training. Modern industry
offers to the majority of people the prospect of more opportunities for
cultivated leisure. It is arguable on the other hand that as time goes
on work may become more rather than less monotonous for most people.
Training of the individual to use his leisure in ways which will
not bring him into conflict with his neighbours provides a possible
basis for the public discussion of cultural education in what may be
called its æsthetic aspect. The Theory of the Public World does not
necessarily imply that such discussion is valueless. It does not lead
to the conclusion that the æsthetic side of education is unimportant.
It does necessitate a reconsideration of the attitude which the teacher
should be encouraged to adopt. A modern theory of education should
begin by defining the respective spheres of _privacy_ and _publicity_.
I shall illustrate what I mean by privacy with special reference to
the teaching of poetry in the school. I can see no good reason why
a child should be expected to like Keats’ _Ode to a Nightingale_. I
can see excellent reasons why he should know that it was written, and
where to find it. One of the characters in a play by Eugene O’Neill
is made to say: “I love dynamos. I love to hear them sing. They’re
singing all the time about everything in the world.” Mrs. Fife was an
American. She had almost certainly never heard a nightingale sing. In
England, where the nightingale is an indigenous species, its overrated
vocal performances are hardly less familiar to the average child. To
the majority of people brought up from childhood in urban surroundings
dynamos are closer to Nature. They are things that they can see and
hear. Churchyard owls and beds of asphodel belong to books rather than
to life. For the average citizen it may be valuable to know that the
word Hippocrene does not mean the same thing as hippopotamus. From
every point of view enlarging the vocabulary is an important part of
education. Enlarging the vocabulary and developing an interest in
literature as a means to cultivated leisure in adult life are entirely
separate issues.
I once asked a friend who is a biologist whether he was interested
in modern poetry. He hesitated and replied that he quite liked
_Evangeline_. I am almost certain that he had not opened Longfellow’s
works since he was a schoolboy, unless he had received from an aunt
one of those editions which are bound in mauve suède and sold for
Christmas and birthday gifts. He was no less truthful than most of us.
He displayed a motor reaction which can be evoked from many people who
have been educated on the assumption that the teacher’s business is
to cultivate “good taste.” If one of our leading dailies were to make
favourite English poets the subject of a prize competition, it is safe
to predict that Wordsworth would receive many more votes than William
Blake. It would be interesting to ascertain the number of hours devoted
after school age to the perusal of the works of Wordsworth and Blake
by those who would vote for one or the other. I know of no one who has
undertaken this task as a thesis for the Ph.D. degree; but I would
hazard the surmise that the aggregate would favour Blake rather than
Wordsworth. The modern teacher has abandoned the exegetical method in
favour of the “play way.” But the advocate of the play way is no less
certain that if he likes Shakespeare, his pupils ought also to like
Shakespeare. If he is really interested in Shakespeare, and has an
engaging personality, he may succeed so long as they remain under his
influence. It does not follow that the pupil will carry into adult life
the means of enjoying his leisure in a way that will not be a nuisance
to his neighbours.
In discussing the æsthetic aspect of education, it is difficult to
exclude the intrusion of one’s private values. I am aware of this
difficulty. Anything which I proffer to the discussion is of a very
tentative nature. The cultivation of taste involves two separate
issues. Conventionally it signifies the existence of some fixed
standard of correct enjoyment. The cultivation of good taste in
this sense is only justifiable if we have satisfied ourselves that
philosophy can provide a rational sanction for the affirmations
of æsthetic experience. If we have reached the conviction that the
affirmations of æsthetic experience have no status in the Public World,
we have no justification for interfering with another person who
reads John Oxenham’s _Bees in Amber_ in preference to Conrad Aiken’s
_Punch the Immortal Liar_, or the works of Miss Ella Wheeler Willcocks
in preference to the sonnets of Edna St. Vincent Millay. I think
experience would sustain the statement that people who habitually read
Coventry Patmore or Francis Thompson are temperamentally different from
people who prefer to read Osbert Sitwell or Carl Sandburg. I suspect
too that such temperamental differences exist even in early childhood.
They are therefore outside the realm of argument or education. On the
other hand, experience convinces me that many would read poetry in
adult life, if they had not been repelled in childhood by the sickly
romanticism or pedantic archaicism of those writers who are usually
exhibited as models of good taste. Possibly a number of people who read
Mr. Kipling would not do so if they had access to more sophisticated
forms of entertainment. Many others do not read poetry and rather
despise those who do, because they have never realized that the subject
matter of poetry is not necessarily circumscribed by a holistic view
of sex or confined to the domestic affairs of the minor Greek deities.
There is a legitimate sense in which taste can be cultivated. We may
go through life impoverished, because we have never been introduced to
sources of satisfaction which might enrich our experience. It is the
proper function of the educationist to acquaint us in early life with a
great variety of opportunities of socially agreeable behaviour. Having
done this, he or she must leave us to select what is most appropriate
to our temperamental peculiarities.
The technique of education in its æsthetic aspect has received
less thoughtful attention than its more practical problems. After
a succession of ludicrous experiments, educationists now realize
that the attendance of art galleries is not increased by forcing
children to draw one white cone, a pyramid and two cubes piled up on
a drawing-board. It is also recognized that a weekly period devoted
to the tonic sol-fa notation does not make a nation musical. I would
suggest that the disappointing results of æsthetic education are
pre-eminently due to the fact that educationists have never recognized
that æsthetic values do not belong to the public world. I would go
further and suggest that more positive results might be achieved, if
our educational practice were founded on a recognition that æsthetic
preferences come within the proper domain of what I have called
_privacy_. Education has too long been dominated by the æsthete
who regards his own values as having some final and transcendental
sanction. Because temperaments differ, æsthetic education can never
leave a permanent impress on the majority of people, so long as it
is dominated by a school of private opinion, whether that school is
Shakespearian or Shavian, Realist or Vorticist. The rising influence
of science, if it checks the influence of pontifical æstheticism is
calculated to reinforce rather than curtail the æsthetic aspect of
modern education.
In _Science and the Modern World_, Dr. Whitehead has maintained the
contrary view. He affirms that “in regard to the æsthetic needs
of civilized society the reactions of science have so far been
unfortunate.” I do not think that there is any historical justification
for this assertion. During the Renaissance there was a very intimate
connexion between the progress of biological science and the
development of painting and engraving. Human beings and horses had
been represented with some measure of biological fidelity in Greek
plastic art. But realistic treatment of animals and plants in general
was a late development of the Art of the Renaissance. Most of the
descriptive biology of Aristotle, of Theophrastus, and of the Arabs was
a dead letter when it filtered into modern Europe. The descriptions in
the Greek and Arabic herbals were too indefinite to be adequate for
purposes of identifying species without the aid of good illustrations.
Anyone who will take the trouble to refer to the originals of Conrad
Gesner’s _Natural History_ or Gerrard’s _Herbal_ will appreciate the
statement that Dürer initiated a new epoch in biology by depicting a
recognizable rabbit. It was no fortuitous circumstance that Leonardo da
Vinci was both a distinguished anatomist and a distinguished painter.
The naturalist of the Renaissance had to be an artist. There were no
cameras. The tradition of Realism in Art developed side by side with
the progress of medicine to meet a need which no longer exists.
To-day we have cameras, and Realism in Art is declining. I venture
to suggest that the invention of cinematography, though still in
its infancy, is unfolding new artistic horizons. It is still common
to find that educated people disregard its latent possibilities as
Puritan England despised the stage. It is unwise to assume that
Victorian ideas of Art have more finality than future generations will
in all probability ascribe to them. Silas Marner, who had never seen
a skyscraper or a dynamo, could not be expected to like the _Cabinet
of Dr. Caligari_ or Capek’s _R.U.R._ For the same reason we should
not expect Whitechapel school-children to enjoy Landseer and the
Lake poets. To the Victorian æsthete a machine and a factory were
necessarily ugly. The Immortal Stagyrite had settled the criteria of
beauty two thousand years before. It is worthy of note that American
industrialism rarely impresses the visitor with that drab monotony
which is so characteristic of the English town. This may be partly
because American education has been less dominated by the æsthetic
predilections of a pre-scientific era in human history. The increasing
importance of science in education need not react unfavourably on its
artistic function. If it has done so, it is not because science has at
any time dominated our conception of a cultural education. The cultural
value of science has hardly been recognized as yet.
§2
However defined, education includes fitting the individual for some
kind of productive activity. On this account the place of science
as a part of vocational training is now securely entrenched in our
educational system. The hard logic of economic necessity has forced us
to make more and more concessions to natural science. It is doubtful if
more than a handful of educationists see clearly that those changes in
the structure of civilization which have necessitated such concessions
have made scientific study of paramount importance in cultural
education. The terms cultural and vocational are, by many people,
still used coextensively with literary and scientific. It is true that
science is not directly concerned with the æsthetic side of education.
If in addition our definition of culture includes an intelligent
orientation to human society, ignorance of science is incompatible
with a cultured outlook in the present age. The special features of
modern civilization depend on the extent to which scientific knowledge
has been applied to the conquest of Nature by mankind. The picture of
the physical universe which science offers for our contemplation is
therefore the nucleus of what is socially most vital in our time.
The task of giving science a place in our conception of cultural
education presupposes a good deal more than the addition of obligatory
science subjects to the curriculum. Chemistry is usually taught in
universities so as to ensure that the student will be able to discharge
with competence the work of an analyst in the public service. It
is also possible to teach the same subject in such a way that the
student gets some glimpse of the adventure of scientific knowledge,
some insight into the method of science as a way of dealing with
human experience, some apprehension of the challenge which throughout
the ages science has issued to comfortable beliefs and established
traditions. This attitude to the study of science is still rare among
those who have been educated on exclusively scientific lines. The
classically educated person can at least be said to have something
which was once a culture. He has a more or less consistent attitude to
the world around him. In spite of all that is said about the menace
of scientific materialism, a consistent mental attitude is very rare
in scientific men. They usually have two attitudes, one for the
laboratory, one for Sundays and the domestic circle. This is partly
because scientific education has been almost entirely vocational in its
emphasis.
That it is still necessary to emphasize the place of science in
cultural education is a heritage of the humanistic revival. Until
comparatively recent times the leading educationists of western Europe
were agreed that the cultural side of education is satisfactorily
accommodated by a study of two dead languages. The founders of the
Grammar Schools were men who after a life-long devotion to Latin and
Greek had found in the classical authors a link with the living past
and a real source of æsthetic delight. Their pupils rarely progressed
sufficiently far with the rules of accidence and syntax to acquire
any genuine knowledge of classical literature or ancient history. The
number of modern Englishmen who enjoy Scandinavian drama or Russian
fiction through the medium of translated works is certainly greater
than the number who deliberately read the classical tragedians in the
original. Leaving out of account professional historians, the number
of people who have been inspired to learn more about ancient history
through dipping into Mr. Wells’ _Outline_ is probably greater than the
number of those who as schoolboys acquired a taste for history from
construing Xenophon, Thucydides, Cæsar and Quintus Curtius Rufus. The
grammarians, in the words of Mr. Wells, were fumbling with the keys of
the past to open the doors of a ransacked treasure chamber. It is now
widely recognized that the results of classical education have been
disappointing. In relation to the æsthetic side of education, it cannot
be said to have promoted the growth of what Dr. Whitehead calls “a
living art which moves on and yet leaves its permanent mark.” Socially
it started at the wrong end. An intelligent orientation towards
society presupposes a knowledge of the history of human society. It
also presupposes on the part of the individual a vital appreciation
of his own surroundings. Unfortunately, the obsolescence of classical
education is not the result of a reasoned conviction of its cultural
inadequacy. The influence of the grammarians declined because they
could not meet the practical requirements of our age.
Science came to occupy its present status in the school curriculum
as part of a comprehensive change in educational outlook associated
with the rise of the manufacturing class to political power. The
aristocratic tradition in education, with its humanistic bias towards
formal logic, Latin and Greek, sufficed so long as the Church and
Law were the principal professions which attracted the sons of the
well-to-do. The coming of the machine age opened up new horizons of
professional activity necessitating prolonged and highly specialized
training. With the development of new international communications
came a greater demand for acquaintance with the living languages of
a nation’s customers abroad. Initially the demand for science in
education was justified on purely vocational grounds, a fact which has
given scientific education on every step of the educational ladder a
fundamentally utilitarian tendency. In our own time the demand for
biological instruction as a school subject has been very largely
motivated by a utilitarian objective. The public is told how important
it is that our future citizens should realize that by studying the
domestic habits of the mosquito biologists have made it possible for
engineers to construct the Panama Canal. It is further argued that
if our future citizens were brought up to entertain a more lively
respect for them, in short, to give them a greater measure of financial
support, biologists would very shortly eradicate house-flies, idiot
children, bean-weevils and bed-bugs; make it possible for anxious
parents to have a family of twelve girls at will and keep the working
classes alive exclusively on tinned food.
The tremendous development of scientific knowledge which followed
the coming of the machine was a phenomenon whose social consequences
could hardly be envisaged by those who put forward the plea for
scientific instruction in the earlier part of the nineteenth century.
To-day we can look back over the last century and a half on the growth
of a form of civilization which owes its special characteristics to
the power over nature which scientific knowledge has conferred. It
is now possible to realize that an appreciation, not merely of the
conclusions of science, but of the experimental temper of scientific
reasoning, has become essential to the intelligent orientation of the
individual to an environment more and more determined by the creative
thought of science. The classical ideal which is compatible with the
view that a man may rightly be considered educated and remain ignorant
of man’s place in the physical universe, as depicted by science for
our imaginative reflection, is an arrogant and impertinent pretension
which thinking people will soon cease to countenance. Those who have
pressed the claims of scientific education have concerned themselves
very little with providing a substitute for what the advocates of
classical humanism honestly attempted to achieve. The influence of the
Utilitarian School of educationists has superseded what might be called
the School of Grammatical Paleontology. One result is that education
has been made accessible to a much greater proportion of people. There
has grown up a generation of educationists who recognize that heaven
does not necessarily lie about us in our infancy. On all sides we see
the determination that children shall enjoy school. We now have in
our midst the Aimiably Maternal School. There is a danger that the
Aimiably Maternal educationists will encourage children to regard
childhood as an end in itself; but it is to them that we must look for
the development of the æsthetic side of education. They are replacing
the cultivation of “good taste” by the aim of self-realization. They
are giving _privacy_ its proper place in the theory of education. The
domain of publicity--the task of emphasizing the cultural importance
of science--still lies with the future. There are, it seems to me,
two outstanding pre-requisites for the execution of this task, a
recognition of the importance of biological instruction in the school
and a closer relation between the teaching of science and of history in
the university.
§3
A broader conception of the human significance of science will never
be achieved until biology occupies a position of greater importance in
the school curriculum. Biology contains within its province a point of
contact with human life on the one hand, and the methods of an exact
and experimental science on the other. Fortunately the educational
value of biology is beginning to be recognized. The fact that biology
has so recently been added to the school curriculum and that, by no
means universally as yet, offers a singular opportunity for educational
experiment. It is an opportunity which physics and chemistry,
hampered by a heavy load of conservative tradition operating through
cut-and-dried syllabuses and stereotyped textbooks, cannot provide.
It is an opportunity which carries with it both responsibilities
and dangers. The teaching of biology is in one way, and here lies
the special opportunity, most fitted to initiate the pupil into the
implications of the scientific outlook in human life. Biology handles
the kind of matter, living matter, of which human beings are to us the
most fascinating, entertaining and familiar varieties. On the other
hand, and in this lies the chief source of danger, biology being a
young science with a far greater diversity and complexity of subject
matter, is less fitted to demonstrate the essentials of scientific
reasoning than a more firmly grounded, older and more exact branch
such as physics. We must face our task with a clear recognition of the
danger that biological teaching will be made an excuse for supplanting
the mental discipline of physics and chemistry by a miscellany of
easily memorizable facts which illustrate no conclusions that can
properly be dignified by the name of scientific principles. This is
certainly what will occur if the Utilitarian school, with its emphasis
on where house-flies go in winter, is given full scope in constructing
our school syllabuses.
In the early stages of the development of any branch of knowledge there
is a period when it is necessary to amass facts indiscriminately,
because the significance of particular classes of facts is not as yet
apparent. For the study of living organisms in particular an enormous
amount of detailed observation was essential before it was possible
to formulate the mechanical problems which living matter presents for
solution. In such an early stage it is a frequent and fruitful source
of misunderstanding to dignify by the name of laws and theories,
generalizations which are not scientific principles, but merely
mnemonics. Biological textbooks are to this day full of architectural
mnemonics. A pertinent instance is the germ layer theory. These have
no relation to the generalizations of an exact science such as the
Kinetic theory of gases or what is even more modestly called Avogadro’s
Hypothesis. Biology in our generation has ceased to be merely an
encyclopædia of descriptive information. It has to-day attained the
status of an exact and experimental science. As such it is a child
of the machine age. The realization of its new status is by no means
universal even among biologists. This fact renders the danger to which
I have alluded especially formidable.
The birth of the doctrine of organic evolution, before the growth of
the modern quantitative study of inheritance and variation, provided it
with an experimental basis as a scientific theory, set biologists to
the task of tracing hypothetical pedigrees. The amassing of an enormous
volume of purely descriptive information acquired the reflected
glory of those profound cosmological consequences which the concept
of evolution implied. In the latter half of the nineteenth century
the study of structure and activity became completely divorced. As a
separate subject, focused to a large extent on clinical aspects of
its subject matter, physiology branched off independently. Zoology
ceased to be the scientific study of living animals, and became the
architectural study of corpses and corpses malodorously mutilated in
formalin. This development was not without consequences of some purely
practical value. Increased knowledge of the life histories of many
pests and parasites demonstrated the economic value of biological study
to a parsimonious public. Without doubt such studies should continue
to receive the financial support that their immense economic utility
merits. They should be encouraged as technical developments of biology
in the university. Their value is culturally irrelevant to our attitude
towards the scope of biological teaching in the school. In the school
the scope of biological teaching should be based upon the candid
recognition that biology is primarily concerned with the Nature of Life.
This will affect our practice in several ways, which can only be
indicated here in very general terms. Elementary textbooks of zoology
are written in such a way as to conceal the fact that anatomy was
originally an experimental science. Galen had to ligate the ureters to
convince the disciples of Erasistratus that the kidneys are the source
of the urine. In textbooks of animal biology for beginners it is usual
to describe the path of nervous impulse from the skin to the spinal
cord and thence to the muscles, as if the reflex arc were something
which is evident to inspection. A century and a half of continuous
experimental enquiry elapsed between the work of Whyte, who first
located the spinal cord as the meeting-place of “sensory” and motor
impulses, and that of Waller, who completed the accepted schematization
of reflex activity. It is of no educational value to be familiar with a
textbook diagram of the reflex arc, unless the experimental evidence on
which it is based is clearly understood. The teaching of biology can be
as helpful as the teaching of chemistry to illustrate the methods of an
experimental science. This implies that the teaching of animal biology
must be emancipated from the shackles of the Darwinian tradition of
pure morphology. Practical work must include dissection and microscopic
observation; but dissection and microscopic observation must be
supplemented by ample demonstrations of an experimental kind.
To a very large extent the construction of our syllabuses will
determine the method of presentation. The cultural value of all science
teaching is at present hampered by a failure to emphasize the logical
development of its subject matter. In the teaching of biology the
facts of animal structure should only be presented in so far as they
illustrate, and are strictly relevant to, an understanding of the
characteristic properties of living matter. It is still customary
in universities to begin the study of the anatomy of the frog by
describing its external features. This is a purely architectural
attitude to adopt towards an animal. If we must start with the
external features of the frog, let us first study some characteristic
manifestations of its ever-changing reactivity, such as colour response
or mucus secretion, and having defined the experimental conditions
which determine these reactions, proceed to examine their structural
basis in as much detail as is relevant to our purpose. It is essential
that continuity of theme should be developed in relation to a
consideration of the organism as a dynamic system.
The teaching of biology for its cultural value also implies the need
for the fullest co-ordination with the teaching of chemistry and
physics. As every educationist will agree, this is desirable not only
from the cultural standpoint, but to get the best practical results.
Here there should be no difficulty for the scientifically trained
teacher. Such simple demonstrations as the experiments of Lavoisier
and Priestley on respiration, or of the action of a digestive ferment,
will reinforce the teaching of chemistry and may even quicken an
interest in chemistry and physics, where it had not existed before.
If an elementary introduction to Mendel’s laws illustrated on a
comparatively inexpensive scale with poultry be included in the later
stages of a school course, the teacher could take the opportunity of
experimentally demonstrating the elementary laws of probability. This
would provide a helpful introduction to a branch of algebra which in my
opinion is relegated to an unnecessarily and regrettably late stage in
mathematical education. Being the youngest born, biology in the schools
is the Cinderella of the sciences. Some of our headmasters appear
to think that anyone is good enough to teach it. It is obvious that
desirable results will not be accomplished, if biology is taught by
teachers with an exclusive training in descriptive biology unfortified
by the study of physics and chemistry.
The æsthetic satisfaction derived from contemplating Man’s place in
Nature will itself endow the study of biology with cultural value for
a few people. But as a school subject biology can make a more general
appeal to consideration as the basis of a new humanism. Few things in
human life, if any, are the source of more universal inconvenience
than sex. The difficulty of satisfying our appetite for food does not
present any special difficulty so long as society provides us with
the opportunity for work with adequate remuneration. In the domain of
sex the difficulty of accommodating physiological necessity to social
convenience extends to all ranks of society. In the nursery rhymes
of childhood, in the fiction on which our adolescence is fed we are
accustomed to romantic expectations which permanently unfit us for the
realities of sexual experience. In adult life religious teaching and
the legal code reinforce the magical view of sexual behaviour. Even
among educated people few possess a secular vocabulary with which to
discuss sex intelligently. It would be better for a child never to have
heard of Plato than to reach puberty without a scientific knowledge of
the nature of sex. If the introduction of biological instruction into
the school sweeps away the holistic idea of romantic love, and helps us
to envisage the difficult problem of congenial mating as a complex of
diverse and separable issues, it will achieve the greatest reform which
has hitherto been made in the educational process.
§4
Science will not occupy its proper place in cultural education so
long as the scientific man himself is a man of narrow intellectual
interests. In the university the task of educating a scientifically
trained student with a broader outlook than we are accustomed to expect
must begin in the way we teach science. To a minor extent this will be
encouraged by breaking up our existing -ologies into smaller units. A
biologist should not be prevented from studying physical chemistry to
an advanced stage because he has neither time nor inclination to devote
to a tedious routine of analysis devised for those who are going to
take positions in dye-works. A physicist should be permitted to know
something about the nature of biological enquiry without wasting half
a year cutting hand-razor sections of stems and learning the names
of pressed flowers, fish-bones and beetles. But the real romance of
science, the realization of scientific understanding as a great mental
adventure, will only be achieved when our teaching of science is
brought into much closer relation with the study of history.
There are several good reasons why the historical background of a
scientific problem should always be brought into sharp relief in
university and for that matter in school teaching. The student of
mathematics who in the course of a single introductory lecture on
the calculus completes the differentiation of the function _x^n_
might be encouraged by the knowledge that he has covered in an hour a
problem which took the generation of Barrow, Newton and Leibniz about
forty years to solve. I venture to think that the introduction of a
little history would make the first steps to algebraic symbolism more
interesting at the school stage. At present it is usual to teach one
subject algebra, in which certain conventions are laid down like the
rules of bridge, and another subject geometry, in which the pupil
learns at a comparatively advanced stage that the proposition
_a(b + c) = ab + ac_ physically corresponds to a statement about the
addition of areas of rectangular figures. The child is rarely, if
ever, told how, from the discussions of such geometrical problems, the
Hindu rhetorical algebraists of the first six centuries A.D. were led
to deduce certain rules governing the properties of numbers, and how
subsequently the Arabs simplified these rules by the development of a
symbolic shorthand. Most elementary textbooks of physics contain _ad
hoc_ proofs of certain verifiable consequences of the inverse square
law in electrostatics and magnetism. Why anyone should ever have
attempted to investigate the applicability of the inverse square law
to electrostatic and magnetic attractions is rarely divulged. A little
information about Newton’s interpretation of Kepler’s laws and the
development of the theory of gravitational attractions subsequent to
Newton’s work would suffice to show how natural it was that Cavendish,
Coulomb and Gauss should test out the inverse square law in electricity
and magnetism before exploring other possibilities.
Sometimes for an entirely different reason a knowledge of scientific
history will assist the teacher to a clearer exposition. The
logical technique initially employed in elaborating new scientific
generalizations is often capable of a much greater measure of
simplification. The teacher who understands the history of his own
branch of science will be more likely to realize this. It is generally
held that electricity is a suitable branch of science to teach at
the school stage. Electricity is much more directly related to the
interests of the average boy than any other branch of physical
science. In everyday life it is the phenomena of current electricity
which we encounter chiefly. Historically, current electricity was
not subjected to exact treatment till the phenomena of electrostatic
attraction and of magnetism had been considerably elaborated with the
aid of mathematical conventions drawn at first from the theory of
gravitational attraction and later from the study of hydrodynamics.
It thus happened that Ampere defined the unit of current in terms
of magnetic potential. For this reason textbooks of physics usually
introduce current electricity after a preliminary treatment of
frictional electricity and magnetism. To-day the international unit
of current is based on electrolysis. The chemical definition of
current involves nothing more than the use of simple proportion.
Given a generator and a chemical unit of current the definition of
resistance follows empirically from studying changes in the dimensions
and materials of the circuit. The idea of electromotive force can be
deduced by studying the effect of changing the generator or tapping
off current from different parts of a fixed circuit. Ohm’s law then
emerges self-evidently in the course of the enquiry. At no point is
it necessary to introduce difficult ideas imported from magnetism and
beyond the range of the pupil’s mathematical knowledge. In testing
out Ohm’s law, in measuring electromotive force or resistance,
the galvanometer is only used as a null-point instrument. For an
intelligent grasp of the meaning of current, potential and resistance
it is therefore only requisite to know that magnets exist and that
a suspended magnet is deflected in the neighbourhood of a current.
Examination syllabuses are customarily constructed on the assumption
that it is impossible to teach current electricity without first
teaching frictional electricity and magnetism. There is no good reason
why frictional electricity and magnetism should be introduced at an
early stage. The only reason why the fundamental ideas of current
electricity are made to appear so formidable is to be found in the
history of the subject. The teacher who knows the history of his
subject thoroughly will be more likely to realize this.
The teaching of current electricity illustrates the possibility of
co-ordination in science teaching in the school. Faraday’s laws of
electrolysis are generally demonstrated at a fairly early stage in the
teaching of chemistry. At this point the definition of the electric
current and its measurement is most appropriately introduced. In a
school where biology is taught a physical model will prove valuable
to demonstrate the effect of fluid friction on the flow of liquids in
explaining why blood spurts from an artery and trickles from a vein. By
what Dr. Wrinch calls the principle of true analogy the same mode may
be used to illustrate the ideas of potential, current and resistance.
But the fundamental importance of the historical method in science
teaching lies in the fact that no perspective of the relative
significance of different types of scientific hypothesis, and no
realization of the intellectual potentialities inherent in a scientific
generalization, can be obtained without a knowledge of the kind of
intellectual difficulties that new scientific ideas met with when they
were first formulated. Half-hearted attempts are made to introduce
historical information into scientific textbooks. They usually lay more
emphasis on the outstanding contributions of individual men of genius
than upon the development of ideas. If historical information is only
used as a means of promoting ancestor worship, it does more harm than
good. Histories of science are not invariably written by men who have
a clear perspective of the general intellectual, and it might be added
economic, tendencies of the periods with which they are dealing. For
that reason they fail to inspire a critical and enquiring attitude
in the reader. Scientific enquiry is essentially progressive. Yet
scientific study does not invariably produce a progressive intellectual
outlook. It is, I believe, because so few who study science attempt
to envisage the generalizations of their subject in their historical
perspective, that the product of a scientific type of education is
often a more conservative type than the historian or even the classical
humanist.
A knowledge of the historical background of science is a necessary
prerequisite to an apprehension of science as an intellectual adventure
and a challenge to traditional ideas. To possess such an historical
background necessitates a knowledge of human history as well as a
knowledge of science. The creation of a new humanism based on the
claims of natural science is a task which will require a reorientation
of historical and scientific studies throughout the educational system.
In the school this task is being simplified by the revolt against a
tradition which laid too much emphasis on purely national issues.
Teachers of history are ceasing to believe that children should be
taught to draw maps of the battles of Oudenarde and Malplaquet. The
history of ideas is beginning to assume more prominence than the
technicalities of military strategy.
In a few universities departments have been founded with the aim of
studying the history of science. There are at present all too few
scientists who like Dr. Singer are capable of promoting a deeper
knowledge of the progress of science. The history of science is
not a history of pure deduction. It is not a meaningless incident
that Leeuwenhoek, a Hollander, used pepper suspensions to make the
first cultures of micro-organisms. It is not a mere coincidence that
Leeuwenhoek and Hartsoeker simultaneously discovered the spermatozoon.
The first microscope was the signal of a new era in biological science.
The invention of the microscope followed shortly after Descartes
formulated the laws of refraction of light. It is a task for the
historian of science to place this sequence in its proper relation to
the interests stimulated by the great navigations, and the struggle
for sea-power. A great measure of encouragement to the study of the
history of science in the university would, I believe, infuse new ideas
into the study of both history and science. It would also re-establish
a vital relation between philosophy and science. Instruction in the
history of scientific thought could be a nucleus for the synthesis
of each fragment of the mosaic of natural knowledge into a coherent
picture of the public world as we know it through the medium of
scientific enquiry. The philosopher of the future may well be the
historian of science.
XII. THE PUBLICIST STANDPOINT AND HOLISM
“I am no coward who would seek in fear
A folk-lore solace or sweet Indian tales:
I know dead men are dead and cannot hear
The singing of a thousand nightingales...”
James Elroy Flecker
§1
The history of philosophy has witnessed a succession of makeshifts to
accommodate the utilitarian claims of science and the rival demands
of what Robert Briffault appropriately calls custom thought and power
thought. At every stage in the advance of scientific knowledge new
territories have been wrested from the domain of custom thought and
incorporated within the legitimate province of scientific method.
Each new annexation has called forth some new compromise to meet the
requirements of power thought. Scientific hypothesis is ethically
neutral. The politician insists that his theories of human conduct
must present an aspect of academic plausibility. Darwin’s doctrine
undermined the complacent dualism which had kept philosophy and
natural science in water-tight compartments for centuries. It produced
a vigorous revolt against supernatural beliefs. In our generation
unbelief has spread to all sections of the community with results that
are disquieting to those who pursue the study of philosophy in the
hope of rationalizing their social prejudices. It is high time for
make-believe to stem the tide of unbelief. Inevitably a new compromise
emerges to meet the new situation. Beneath its downy wing holism
takes all that mechanistic science can offer to industry and all that
statesmanship can cull from metaphysics.
“The time has now come,” writes Dr. Haldane, “for giving decent
burial to the mechanistic theory of life in the same grave with
the vitalistic theory.” I agree with Dr. Haldane in so far as many
questions which were contested thirty years ago by those who called
themselves mechanists and vitalists have ceased to be regarded as being
so fundamental as the contestants imagined or even as being amenable
to a final decision. Although the publicist standpoint is admittedly
a rehabilitation of the mechanistic theory in the light of those
biological developments which have brought into being the behaviourist
standpoint in psychology, I have myself preferred to use the term
_publicist_ for my own point of view. It is rather tiresome to be
forced to answer for every misdemeanour of somebody else who happens to
call himself a mechanist or a behaviourist. I can therefore sympathize
with Dr. Haldane’s disinclination to accept the vitalistic label for
his own beliefs. I differ from Dr. Haldane in thinking that we are any
nearer to a final reconciliation between a difference of philosophical
outlook that arises from the fact that philosophers have different
temperaments. If we have outgrown the differences of statement which
underlie the controversy between the older vitalistic and mechanistic
standpoints, we have not outgrown the differences of temperament which
underlie the existence of the two theories.
I have no disposition to state dogmatically the possibility
of explaining all the properties of living matter in whatever
physico-chemical terms will be employed two thousand years hence. Still
less am I willing to be responsible for the billiard ball theory of
matter which both Dr. Haldane and General Smuts have identified with
the mechanistic conception of life. I am content to foresee enormous
possibilities for the extension of physical interpretations of the
properties of living matter. I fail to see how human knowledge will
progress on any logical assumption but that implied by the principle
of mechanism in its most general terms. I am not able to accept Dr.
Haldane’s belief that the traditional methods of physiology are
useless in discovering the properties of conscious behaviour, though I
should hesitate to predict, except in a very tentative way, how far we
shall progress in this direction. If I have seemed to exaggerate the
possibilities inherent in the future of biological enquiry, my excuse
must be that my aim is to stimulate interest in a new philosophical
outlook. If there is such a person as the dogmatic mechanist, his views
are not what I imply by the publicist standpoint.
When all this has been said, there still exists a very radical
difference between the publicist standpoint and the holistic to
which Dr. Haldane subscribes. That difference lies in the fact that
the holist denies the possibility that a certain type of logical
procedure is capable of establishing relations between certain realms
of experience. Nobody denies that such relations remain at present
unascertained. Any dogmatism that comes into the discussion is implicit
in the holistic theory. Dr. Haldane’s position is not merely a
rejection of dogmatic materialism. “I am whole-heartedly in agreement,”
he writes, “with General Smuts in believing that anything which can
properly be called scientific physiology is impossible apart from the
assumption of what he has called holism.”
Of holism as a philosophy of biology enough has been said elsewhere.
It contains within it no promise of future progress. Dr. Haldane has
endeavoured to persuade us that this is not so. I am not able to
follow his argument. We have wasted time, he assures us, in trying to
understand the _mechanism_ of kidney secretion, when we should really
have been striving to find out how the kidneys... “engage in their
function of keeping normal the diffusion pressures of water and various
other non-colloid constituents of the blood.” A mechanist, even if we
grant that he is misguided and presumptuous in hoping to elucidate the
mechanism of secretion, is equally concerned with solving the problem
which interests Dr. Haldane. The physiologist who sets out to tackle
it will proceed in the same way as a mechanist, whether he calls
himself one or not. He will not first postulate a wholeness of the
non-colloidal constituents of the blood inexplicable in terms of the
individual constituents themselves.
The physiologist studies the properties of the muscle-nerve preparation
because he believes, rightly or wrongly, that by so doing he will be
guided to interpret how muscles and nerves play their respective parts
in the behaviour of a whole animal. Dr. Haldane himself has devoted
years of research to elucidating the properties of hæmoglobin. I
presume, he has done so in the hope of throwing light on the way in
which the supply of oxygen to the tissues is regulated. Most of his
brother physiologists would agree that Dr. Haldane’s distinguished
researches on the physico-chemical properties of a respiratory pigment,
which is a very small part of the economy of an animal, do tell us a
good deal about what to expect in the behaviour of the organism as a
whole. Whatever Dr. Haldane may say on the platform he is as good a
mechanist as anyone else in the laboratory. Throughout a distinguished
career of research he has consistently concentrated his attention upon
certain limited parts of organisms. His statement that physiology is
impossible without holism must be taken as a _jeu d’esprit_. So long
as biology was dominated by the Aristotelian concept of individuality
it remained descriptive. Physiology began when biologists undertook
the task of interpreting the behaviour of the organism as a whole by
studying methodically the behaviour of its constituent parts. If it be
suggested that there is any other physiology, there is no trace of its
existence.
Perhaps the appeal of holism is partly due to the curious circumstance
that physiologists are notoriously mechanistic about the aspects of
physiology they study themselves, and hardly less often vitalistic
about aspects of physiology with which they are unfamiliar. The divorce
of morphology from experimental biology after the rise of the natural
selection theory tended to produce the zoologist who is exclusively
preoccupied with the anatomy of dead animals, and the physiologist
who is exclusively preoccupied with the casualties of the hospital.
In another place I have attempted to show that Dr. Haldane could
find in modern genetics the clearest evidence that the biologist
only progresses when he interprets his data in the same way as the
physicist or chemist interprets his. In another branch of physiology,
which like genetics lies outside the domain of the clinician on the
one hand and the physical chemist on the other, Dr. Haldane will not
find that the work of Sherrington and Pavlov provides abundant evidence
that the holistic attitude is less impotent to suggest new lines of
experimentation on reflex action or is more useful in promoting an
understanding of the process of learning.
Laying aside the purely biological aspect of the holistic attitude,
there are some more general issues which remain to be discussed. It
is never easy for a hostile party to do justice to the standpoint
of another school of opinion. I hope therefore that I shall not be
accused of drawing a caricature of the holistic theory. To avoid
doing so I shall quote freely from the writings of those who support
it. Holism, as I understand it, differs from the primitive animism
which sees a personal reality behind or within physical objects. It
differs from vitalism which sees an essential gulf between the living
and the non-living. It differs from the common-sense dualism which
invokes Mind as a separate and irreducible concept in dealing with the
characteristics of “conscious behaviour.” The difference lies in this,
that entirely new properties emerge at _various_ levels of existence.
_Between_ these levels we can operate successfully with the atomistic
logic of science, interpreting the properties of a complex system from
a study of the properties of its several constituents. _At_ these
levels we encounter new properties “which,” in the words of General
Smuts, “could never have been predicted from a knowledge merely of the
parts.” General Smuts mentions under the terms Matter, Life and Mind
three principal oases within this desert of uncertainty. Even these
do not constitute regions within which the continuous extension of
scientific method may be applied successfully. Within the territory
of matter “the molecules of water and carbon dioxide are real wholes
with new emergent properties.” Thus physics, chemistry, biology and
psychology are in Dr. Haldane’s terminology “independent sciences.”
As far as I am able to see, there is no room for disagreement about how
the scientist proceeds within these prescribed territories. Scientific
generalizations are attempts to show how the characteristics of complex
systems can be inferred from the properties of their constituent
parts. This means, more specifically, when the problem can be reduced
to mathematical symbolism, that an equation which defines the four
dimensional relations of any system will contain no terms that are
not present in some or other of the equations which determine the
space-time relations of the constituents of the system. This procedure,
admitted Forsyth (1929) in a recent paper delivered to the British
Association, “is very largely justified in principle and by results.”
He continued to remark, in conformity with the standpoint developed
in these essays, that “the question is not that of a division of
spheres or levels of existence, some of which are capable of complete
explanation on mechanistic principles, while others are incapable...
for there is no sphere which is not in any degree susceptible of the
application to it of the terms and categories of mechanism.”
“Nevertheless,” he contends, “it is gradually coming to be
recognized that this procedure gives only a partial explanation
of _any_ natural process. There is, in any complex process, a
principle of synthesis involved, such that, instead of the whole
being the mere sum of the parts and being explicable by the mere
composition or combination of the parts, it is rather the case that
the parts can only be explained by reference to the whole, since
they are modified by their relation to it. If so, mechanism must
be supplanted, or at least supplemented, by a mode of explanation
that gives due regard to this. This principle of wholeness or unity
is exemplified in many different spheres of fact, e.g. in atomic
structure, in chemical synthesis, in the life of an organism and
even in the character of the single life-cell, in the processes
of perception and volition, and also in so-called reflex action,
in the development of personality and the attainment of social
control. Holism, then, signifies that everything in the universe is
in some form or another, and in greater or less degree, potentially
or actually, an organic whole; that as anything develops to a
fuller realization of its potentialities or a fuller perfection
of its nature, it becomes more truly such a differentiated and
yet unified whole; and that, by implication, the universe itself
is an infinite organic whole.... This involves that nothing in
nature can be explained merely as the result of preceding processes
or anterior stages of development. The lower or simpler is the
condition without which the appearance of the higher or more
complex would be impossible; but the development to higher levels
is possible at all only through the impulse to organic unity or
synthesis under the controlling influence of the infinite whole.”
There exists no difference of opinion concerning the statement that
there emerge at different levels of complexity in natural phenomena
specific properties which cannot as yet be deduced from a knowledge
of simpler systems. Holism seems to imply the further qualification
that such properties will never be interpreted in this way. If I am
right in my understanding of the holistic standpoint, I am at liberty
to leave the onus of proving so dogmatic a conclusion on the shoulders
of those who assert it. I am prepared to go further and point out
certain difficulties in the way of proving it, difficulties which,
in the existing state of knowledge, appear to me to be insuperable.
The first is that of explaining why, if physics, chemistry, biology,
etc., are intrinsically independent types of enquiry, it happens that
there exist such extraordinary similarities in their procedure. The
use of the phrase “scientific method” implies that such similarities
do in fact exist. Dr. Haldane’s many distinguished contributions to
the advance of physiology might be cited to show how much biology has
in common with physics and chemistry. A second difficulty which arises
is of a different kind, and illustrates the fundamental similarity
of temperament which unites the vitalistic and holistic theories.
Scientific investigation is constantly shifting the levels at which
new irreducible concepts must be invoked. This permits us to entertain
the suspicion that _emergent_ properties are only properties about
which we are ignorant. We are under no necessity to regard the present
classification of the sciences as anything more than a convenience
for arranging time-tables in educational institutions. Before the
enunciation of the first law of thermodynamics by Mayer and Joule,
heat was a branch of physics quite as separate from mechanics as is
chemistry from physics to-day. Organic chemistry to Henry was not, as
it is to our generation, the chemistry of the carbon compounds. It was
a field in which emerged something “peculiar to animated bodies and
superior to and different from the cause which has been called chemical
affinity.” In the same year as that in which Henry expressed this view
Wöhler succeeded in synthesizing urea. Why should we be so certain that
our present classification of “independent” sciences will, like the
poor and the Roman Church, be always with us? To this question I can
see no appropriate reply from the holistic point of view. Unless holism
can provide us with a clue that will enable us to distinguish whether
an impasse in scientific enquiry is due to the imperfection of our
knowledge or to the emergence of new properties as “creative” entities,
its acceptance could only have the sinister effect of holding back
scientific investigation.
On its negative side the holist goes much further from what might
be called a centre programme than does the dogmatic mechanist. The
principle of mechanism or experimental determinism is compatible with
the recognition of different levels of complexity or wholes; for what
is analysable is complex, and what is complex consists of interrelated
parts which together constitute a whole. Holism on the other hand
provides us with no explanation of why the principle of mechanism is so
astonishingly successful. The logic of science is inadequate according
to General Smuts. Dr. Haldane asserts that the method of the biologist
is different from that of the physicist. We are not told how we can
proceed to invent a new and equally successful logic. We are not told
in what precise respect the method of the biologist does differ from
that of the physicist. On its positive side holism leaves us waiting
for a new revelation. Holism is sometimes referred to by its advocates
as a category, sometimes as a principle. What the _principle_ of holism
can do for us remains to be seen. Its popular appeal resides in its
promise to restore to ethical values a rational basis. I suspect that
this promise is a general election promise.
Though holism does not assume, like the cruder forms of vitalism, a
specific élan vital or entelechy, it differs from the less explicit
vitalistic theories in detail rather than essentials. In a similar
way, the alternative view which I have called publicism is a modern
development of the mechanistic conception of life. What I define as
the publicist standpoint in philosophy is distinguished from the
traditional mechanistic attitude in physiology by extending the limits
of verifiable knowledge. To a large extent traditional mechanistic
physiology investigated the behaviour of an organism in so far as
its behaviour can be predicted, when all synchronous conditions
are rigidly controlled. It adopted a frankly agnostic attitude to
those characteristics of behaviour in which the antecedent situation
is pre-eminently significant to the co-ordination of stimulus and
response. The Vitalist school recognized the existence of a definite
problem in claiming that a complete solution of the Nature of Life
must take into account the problem of consciousness. They failed to
indicate the precise requirements of the problem, and they therefore
failed to suggest the requisites for its solution. Their assault upon
the mechanistic position collapsed, because they did not state what
precise characteristics of the behaviour of living systems are defined
by the term consciousness. If the concept of consciousness is to be
made clear, it is first necessary to state what properties of the class
_living systems_ are denoted by its use. This necessitates a definition
of the characteristics of conscious behaviour, and an investigation of
the way in which it is possible to investigate them. Only when this
task is accomplished, can we claim to have undertaken a philosophical
exposition of the Nature of Life. Vitalism failed to define the concept
of consciousness, because it did not make the necessary distinction
between its public and private components. The characteristic of all
essentially private statements is the supposition that the means is
referable to the end. The characteristic of all essentially public
propositions is that the end is considered in connexion with the
means. Traditional mechanism disregarded the problem of consciousness.
Traditional vitalism assumed that it is impossible to discuss the
characteristics of conscious behaviour without introducing teleological
implications. The supreme philosophical importance of the work of
Pavlov’s school lies in the fact that it has inverted the traditional
way of looking at the problem of consciousness.
In stating the essential features of the publicist standpoint, I
shall indicate first its significance in current biological thought
and second its attitude to the scope of philosophy. In its purely
biological aspect the publicist standpoint recognizes the folly of
stating dogmatically the possibility of reducing all the properties
of living matter to physico-chemical terms. On the other hand it
recognizes that biology increasingly makes use of physico-chemical
concepts. It also recognizes that we can at present foresee no limit to
the successful application of physico-chemical concepts to its subject
matter. It recognizes the fact that there is no immediate prospect
of reducing the analysis of some of the properties of living matter
to the level of pure physics and chemistry. It also recognizes that
biology has advanced conspicuously in those regions where the biologist
adopts to the subject matter of his enquiry an attitude similar to
that of the physicist in approaching the realm of inanimate nature.
In particular it sees no necessity for the introduction of teleology
into the study of the evolution or behaviour of living beings. It goes
further than the older mechanistic outlook in explicitly renouncing
the traditional dualism of mind and matter, since it envisages the
possibility of indefinitely extending the study of behaviour in
terms of reflex action. The publicist standpoint does not assert the
possibility of disproving the validity of animistic concepts which have
dominated biology in the past, and still persist in a more or less
attenuated form. It relies on the increasing measure of success which
accompanies the application of quantitative and experimental methods of
investigating evolution and behaviour to supersede them. In biology as
in physics magical views fall into desuetude, because more profitable
ways of dealing with phenomena take their place.
Since philosophy itself is part of the behaviour of a particular
organism, the scope of philosophy must, from the publicist standpoint,
bear examination in the light of modern biological concepts. In the
external world of modern physics the distinction between _substance_
and _form_ has been superseded. In the public world of science, i.e.
the external world of physics enlarged to take in the subject matter
of biology, the distinction between mind and matter does not remain
fundamental. What is fundamental is behaviour. This public world is the
domain of socialized belief. Whatever cannot be incorporated in its
ever-widening territory must remain impenetrable through the medium
of discourse. Only propositions that deal with behaviour in its more
extended sense have the property of _publicity_ or social reality.
Reality as a goal of philosophical enquiry is equivocal, since inborn
temperament, digestive activity, erotic preoccupations and various
other factors decide whether to a given individual the constituents
of the public world or of his own private world are more real.
Propositions that have publicity are ethically neutral. The hope that
philosophy can find a sanction for values is therefore illusory.
§2
From the publicist standpoint the business of philosophy is to resolve
the problems of human thought into their public and private components.
The public component of the problem of consciousness is the analysis
of the characteristics of “conscious behaviour.” The private component
offers no profitable basis for discussion. Because traditional
physiology has failed to recognize that the concept of consciousness
has a public component, it has been natural to assume that a
mechanistic explanation of consciousness is pure nonsense. Biological
progress has annexed the study of conscious behaviour from the province
of the private worlds. To the private worlds belong values. Though
differences in values are exaggerated by differences in distribution
of wealth and opportunities of education, there is no prospect that we
shall reach any general agreement by attempting to rationalize them.
In this sense the publicist standpoint is pluralistic. On the other
hand the domain of the public world is always encroaching upon the many
private worlds. In that sense the publicist standpoint tends towards
monism as a limiting case. It offers no short cut to finality. It
recognizes the slow accumulation of scientific knowledge as the only
road to the gradual socialization of beliefs.
In providing no hope for a rationalization of ethical values, the
publicist standpoint comes within the category of the somewhat diverse
schools of opinion to which Bertrand Russell refers as the New
Realism. If it were possible to prove that a particular set of values
is the correct one, a great service could be rendered. People would
then be able to argue about human conduct and artistic productions
without losing their tempers. I fail to see that holism contains any
promise of achieving a consummation so devoutly to be wished. Ethical
systems, as Mr. Russell observes, are usually found to contain a _non
sequitur_. Ethical values represent the private component of social
behaviour. Whether the public component will ever come within the scope
of physiology remains to be seen. Many thoughtful people have been
antagonized towards the mechanistic conception of life, because they
associate it with rash and superficial views about human relationships.
This is an intelligible but not necessarily a logically justifiable
reaction to the naïve self-confidence with which some eugenists, the
“histriometers” and other schools of “intelligence” testers have drawn
pretentious conclusions from the resources of immature biological
theories and inadequately developed biometrical methods. With such
grotesque simplicity did Descartes apply to the physiology of Man
the embryo mechanics of his own time. In reality nothing inherent in
the most dogmatic assertion of the mechanistic conception of life is
logically inconsistent with recognizing the possibility that biology
has many new truths to unfold before sociology can securely build its
foundations on biological theory, the likelihood that sociology must
for long pursue its independent investigation of the natural history
of the human species before it is ready to draw extensively on the
resources of biology. Only during the first half of the nineteenth
century did the concept of Conservation of Energy initiate the era
of modern physiology. Only during the latter half of the nineteenth
century did physical chemistry begin to elucidate those phenomena of
osmosis, colloidal solution and membrane potential now regarded as
fundamental for a mechanistic analysis of the living cell. We have
therefore no reason to suppose that biologists have elucidated in
their own field all those principles which will assist the historian
and the anthropologist to advance further in their studies. Arrogant
and premature generalizations of individual biologists (not always,
or even, I suspect, generally, of the mechanistic persuasion) are
regrettable. They do not justify an attitude of distaste for the
mechanistic conception of life. I have usually observed that the
disposition to interpret the whole field of sociology in narrowly
conceived biological terms is associated with a strong antipathy to the
physico-chemical interpretation of vital phenomena.
In its inability to rationalize values many people will see a serious
limitation of the publicist standpoint. From the days of the
Schoolmen, philosophy has been the “divine science.” It has become
so customary to regard philosophy as the handmaid of theology and
politics, that Henry Sidgwick and others have refused the use of
the term philosophical for a point of view which does not meet this
requirement. We justify this by assuming that the fabric of society
would dissolve, if we believed that our ethical notions contained no
element of finality. It follows that the materialist is to be regarded
as a bad man, and scepticism is coupled with immorality, though there
is nothing in the root meaning of the word morality to suggest why
this should be so. In _Science and the Modern World_ Dr. Whitehead
censures the materialist philosophy of the nineteenth century,
because, he declares, it “emphasized the given quantity of material,
and thence derivatively the given nature of the environment. It thus
operated most unfortunately upon the social conscience of mankind.
For it directed almost exclusive attention to the aspect of struggle
for existence.”[10] I am unable to understand why the political and
ethical shortcomings of the nineteenth century should be attributed to
the influence of materialistic philosophy. The number of materialistic
philosophers was far less than the number of persons who responded
to the appeal of the Tractarian Movement. The Lancashire mill-owners
who were getting rich quickly were the type of men who attended their
Nonconformist conventicles with regularity and subscribed to the London
Missionary Society. Against the view that society must necessarily be
based on a struggle for the means of subsistence continental Socialism
appeared, rightly or wrongly, as a vigorous reaction; and continental
Socialism was the only political movement which can rightly be said to
have been explicitly dominated by a materialist philosophy. I cannot
discern that there has been a very close historical connexion between
people’s religious, philosophical and political views on the one hand
and their social conduct on the other. It is not easy to explain why
the French revolutionaries were anti-clerical and deistic, while the
first chartists and pioneers of trade unionism in England were in close
touch with the Evangelical Revival. Christianity, with its oriental
insistence on the enmity between flesh and spirit and the vanity of
worldly riches, would seem little fitted to provide a satisfactory
rationalization of the sentiment of western civilization. Yet for long
it has done so.
Educational and political institutions grow in response to the
exigencies of human demands which are not necessarily influenced by
any ethical considerations. This may be seen by considering the case
of Mr. X, who lives in Balham and has a passion for pineapples. Mr.
X, not being bothered about metaphysics, is no more disposed than
the majority of his fellow-citizens in Balham to assert any final or
transcendental sanction for his passion for pineapples. He accepts it
as part of his modest unassuming existence. This does not prevent his
writing a letter to _The Daily Mail_, when an import tax on pineapples
makes it impossible for him to indulge his predilection for the fruit
without forgoing other cultural amenities. Meanwhile Mr. Y, who lives
in Tooting and nevertheless cherishes an earnest desire for more and
better pineapples, has written to _The Daily Herald_. Mr. X and Mr.
Y are now joined by Mr. Z of Whitby, whose letter appears in _The
Yorkshire Post_. By this time the Press cannot resist the social
pressure that is brought to bear on the pineapple policy of the party
in power. The evening papers announce in headlines “Nation-wide
movement against Pineapple Protection.” Mrs. J of Houndsditch is
pestering Carmelite House with correspondence on the potato shortage,
and Miss C of Cheltenham is writing to the Chancellor of the Exchequer
about the rising price of prunes. In official circles the determination
to do something which will distract attention from prunes, pineapples
and potatoes takes shape. If the pressure is firm enough the tax
on pineapples and prunes goes, and a promise to give the fullest
consideration to the potato shortage is extracted. Alternatively a
popular film-star is knighted, and the Press, equipped with better
copy, announces that this correspondence must cease forthwith.
There is a difference between a predilection for pineapples and the
pursuit of those amenities which are referred to by more abstract terms
such as _justice_. Pineapples are less frequently a matter of life and
death to those who eat them. Men and women rarely go to the stake or
march to battle for the sake of more and better pineapples. They will
fight for bread, and a roof over their heads and an eight-hour day.
Concerning those forms of social activity which bring us most into
conflict with our fellow-beings we are prone to demand some final or
transcendental sanction for action. Social co-operation is perfectly
realizable without recourse to any such extravagant claims. It is
permissible for a professional philosopher to doubt whether there would
really be more misery in the world if the ethical convictions of human
beings were more lax.
In stating this possibility, I am not endeavouring to give the
impression that I wish to be regarded as a “rational” person. If I
aspire to a more rational outlook than that of some of the writers
whose standpoint I have criticized, it is not because I have no
private world of my own, but because I hope that I am more successful
in separating my public beliefs from my private sentiments. I do not
pretend that I have no ethical prejudices. My ethical prejudices are
as strong as those of most vitalistic philosophers with whom I am
acquainted. Often it happens that my prejudices about conduct are not
the same as theirs. Where we differ I see absolutely no prospect of
arriving at agreement through the medium of argument. I doubt whether
I could ever agree with Dr. Haldane about a just remuneration for
the miner. I accept without hesitation Dr. Haldane’s authoritative
views on miner’s silicosis. There is a world of private values which
I do not and can never share with Dr. Haldane. I have no awareness
of anything in the universe which is anything like the Deity of Dr.
Haldane’s Gifford Lectures. His arguments leave me as unconvinced as I
was before I read them. Dr. Haldane’s Deity is part of Dr. Haldane’s
private world. In general I agree with Dr. Haldane’s interpretation of
the Dissociation Curve of hæmoglobin. If in any points I do not follow
his reasoning, I should probably agree with him on closer examination
of his evidence and inferences. Alternatively I might be able to point
out objections to some of his conclusions. I believe that he would then
examine my objections sympathetically, and, if he could not dispose of
them, modify his views. Dr. Haldane’s Dissociation Curve for hæmoglobin
is not, like Dr. Haldane’s Deity, part of Dr. Haldane’s private world.
It has become part of the public world.
In my own private world the pursuit of intellectual honesty is a matter
to which I attach a good deal of importance. I cannot reconcile with
my notion of intellectual honesty a confusion between the ethically
neutral constituents of the public world and my private convictions
about conduct. When I contend that a rational philosophy must be
ethically neutral, I do not pretend that I have no private world of
my own. I leave open the possibility that the way in which people
come to adopt different philosophical views may one day be made the
subject of public discussion as a problem of human behaviour. In my own
private world a sense of responsibility to other human beings impels
me to refuse to let people think that I am speaking in my capacity as
an expert, when I am really giving vent to my sentiments as a private
citizen. I do not regard my own private world as unimportant to myself.
I choose my immediate friends mainly on the basis of preferences which
belong to it. I am unable to understand the disposition to confuse the
two issues. It is quite possible to separate them in practice. Sir
Charles Sherrington has written an authoritative work on the central
nervous system, the importance of which is a public issue. He has also
published a volume of verse. In my private capacity I happen to like
it very much. I will go further and express the opinion that highly
creative work in science, such as Sherrington’s, is not unusually
associated with an intense system of private values. I admire Professor
Sherrington because of the versatility that makes him both a scientist
and a poet. But I admire him still more because he has not enclosed the
_Integrative Action of the Central Nervous System_ and the _Assaying
of Brabantius_ in one cover as a volume of Gifford Lectures. In
publishing them separately, he seems to me to set an example of honesty
and modesty which some of his contemporaries might well be persuaded
to emulate. William Bateson was a great scientist with very strong
political prejudices with which I have no private sympathy. Bateson’s
intellectual honesty was of so fine a calibre that he consistently and
publicly refused to associate with Eugenic Reform, lest, he explained,
his eminence as a geneticist should appear to give sanction to views
in forming which his personal sympathies were likely to override his
judgment.
More than a century ago David Hume concluded his essay on _The
Academical or Sceptical Philosophy_ by contending that “morals and
criticism are not so properly objects of the understanding as of taste
and sentiment.” If philosophy has advanced at all since the time of
Hume, I am inclined to think that there is less immediate prospect of
making politics a science and more definite information to warrant
the hope that the study of morals may one day become part of an
experimental analysis of how human beings behave. I can see no reason
to suppose that in any other sense will it ever be possible to bring
the affirmations of æsthetic and ethical experience into line with
scientific beliefs. “If we reason concerning beauty,” as Hume observed,
“we regard a new fact, to wit the general taste of mankind or some
such fact which may be the object of reasoning and enquiry.” The rise
of anthropology suggests that there are matters of fact which Hume did
not actually specify. The substance of his argument remains valid.
Science has advanced only when observation has emancipated itself from
the affirmations of æsthetic and ethical experience. To set before us
the goal which Dr. Whitehead proposes may result in hampering science
without fertilizing philosophy. Ethics and æsthetics, like politics and
religion, are, in Trotter’s words, “still too important for knowledge
and remain subjects for certitude, that is to say, in them we still
prefer the comfort of instinctive belief, because we have not learnt
adequately to value the capacity to foretell.” If it was evident to
David Hume, it is still more evident to-day that a “rational and
modest” philosophy will aim less at providing a formula for complete
agreement than at reaching a sensible understanding about matters on
which we should be content to differ.
In undertaking to refute Hume’s arguments Kant assumed the validity
of his conclusions in the method which he adopted. He employed _a
priori_ principles to establish the existence of a “faculty of pure
_a priori_ cognition.” There were at that time no available materials
for a _public_ discussion of the problem which he propounded. In
our generation a new epoch has been initiated by the physiology of
the conditioned reflex. We can now see the correct form in which
Kant’s problem must be stated, if we are to emerge from the dilemma
which arises from the fact that by temperament some philosophers
are extroverts and others introverts. It is no longer a question of
deciding how we come to know, but how we _learn_. If we are too eager
to await the solution of this problem on a purely physiological basis,
we have no need to turn, like Kant, to introspective philosophy for an
answer. The educational practice of Madame Montessori can throw more
light on the origin of the concept of _number_ than Kant’s discussion
of the proposition that seven and five make twelve.
The influence of Christianity in the western world has tended to make
the impersonal detachment of science repugnant to most people. We
are taught that knowledge puffeth up, but charity edifieth. This, of
course, in its own language, expresses the ecclesiastical conviction
that human nature is fundamentally sinful. Whatever we choose to
regard as good or bad, from the biological standpoint human nature
is neither the one nor the other. Man is a very teachable animal. For
that reason it is through intelligent understanding of the springs of
human action that the elimination of social discord is most likely
to proceed. Those who advocate the religious appeal as the basis of
social education have to provide us with an explanation of why the
practical implications of revealed dogma rarely receive any recognition
before the exigencies of economic necessity compel people to act in
conformity to them. No one would deny that religious leaders took a
prominent part in the movement for the abolition of chattel slavery. It
is also a singular fact that the Protestant Churches entered no protest
against the slave-trading activities of Frobisher, Drake and their
fellow-heroes of sea warfare. Nor did they disturb themselves with the
problem until the rise of the factory system had created conditions
which promoted the growth of a different form of labour contract. If
war as a means of settling international disputes is abolished in
our generation, it is not unlikely that religious apologists will be
telling our grandchildren about the prominent part which churchmen
took in founding Peace Societies. They will probably be right. War as
an institution is becoming so menacing a scourge to civilization that
even religious bodies are making themselves active in denouncing it.
But if war is to be denounced on the basis of some revealed and final
view of human conduct, how are we to explain the fact that a negligible
minority of esoteric sects have discovered so significant a conclusion
during the past two thousand years of church history? Should we not
rather say that the urgency of the modern problem has created a new
rationalization? Must we believe that war exists because by nature
human beings are sinful and delight in slaughtering one another? Can
we believe that men are so constructed that they can be induced by
religious conviction to love their neighbours as themselves? Is it not
rather a fact that men are on the whole stupid and indifferent, and
that thoughtful people regard war as an intolerable nuisance, but are
not as yet clear about how it can be avoided? Is it not to patient
study of the ways and means of organizing international government
rather than to ethical dogma or religious fervour that we must look for
the creation of permanent peace?
From a social point of view I do not think it is a demerit of any
philosophy of Life that it provides no pleasant rationalizations as a
guide to polite conduct. One would be more interested in discovering
some way of ensuring how people can be induced to act consistently
with their professions. No religious organization in recent times
has succeeded in achieving this result on a large scale. Theology is
not entitled to criticize a philosophy because it supplies no basis
for ethical values. Theology has failed to show how human beings can
be induced to behave in conformity with the ethical values which it
imposes on them. For the present I shall eat pineapples in preference
to prunes, whether philosophy provides me with a good reason for
doing so or not. Men will not be prevented from demanding a living
wage because philosophy fails to evolve an ethical theory of the
state. A man may be a gourmand without first becoming an Epicurean
or a masochist without embracing asceticism as a moral creed. Ethics
only lie within the scope of the publicist standpoint in so far as
philosophy may indicate the lines along which it is profitable to
investigate how people come to articulate certain combinations of
speech symbols, and how what they say about their actions is related
to other manifestations of motor activity which they display.
§3
I am not unaware of a criticism of the newer mechanistic outlook which
has already been made by an anonymous contributor to _Nature_ in
discussing a symposium at the 1929 meeting of the British Association:
“The extreme behaviourists or biomechanists, perhaps represented at
the conference to judge from reports by Professor Hogben, will of
course refuse to take account of any process which does not admit
of physico-chemical analysis or description--a position that does
not work out well in our daily life and conversation where we have
to allow at every turn for intelligent or even rational purpose.”
The objection implied in these words is closely akin to a fallacy which
is reiterated in most theories of the vitalistic or holistic type. The
publicist standpoint does not imply that we do know everything about
human behaviour. On the contrary it urges that we know in part and we
prophesy in part. I suppose that even the most pessimistic exponent
of the vitalistic school would admit the possibility that science
will in the course of time modify our habits of conversation in many
directions. Everyday conversation always lags behind the advance of
scientific knowledge. It would not be difficult to illustrate how
frequently our habits of conversation in moments of intellectual laxity
are saturated with pre-Copernican and pre-Darwinian views about the
universe. It is in no way remarkable that our habits of conversation
have as yet failed to accommodate themselves to the advances in
biological knowledge that are opening up new fields of investigation
into the characteristics of “conscious behaviour.” I am prepared to be
told that I have repeatedly implied traditional views about thought,
memory, consciousness and the like in writing these essays. As I bring
them to a close I will frankly admit the truth of the charge. The
common language which I was brought up to use does not contain the
words which would be suitable to a thoroughly consistent development of
my present views. I give expression to them, knowing that much which I
have written will appear very foolish to those who enjoy the advantage
of living two thousand years after I am dead. Had I the ingenuity and
astuteness to invent a completely consistent symbolism for the views I
have advocated, I could entertain no likelihood that anyone now living
would read what I have to say. My own inconsistencies and imperfections
do not lead me to infer that human beings will always be forced in
their everyday conversation to discuss the problems of human existence
with all the limitations to which I am subject.
We are told by Professor Eddington and Dr. Haldane that the
abstractions of physical science have taken us further and further away
from Man, the starting-point of our enquiries. Experimental biology in
probing into the traditional distinction between reflex and voluntary
activity permits us to recognize that science is in process of taking
within the scope of its method fields of intimate human interest.
Mechanists of a past generation could not conceive them as capable
of annexation. In bringing us back to our starting-point biology has
strictly adhered to the method of enquiry which has proved successful
in constructing the fruitful abstractions of physics and chemistry.
We can thus look forward to a time when the method of science will
claim for its field everything which comes within the scope of what
people will agree to call knowledge. Because social activity lies
within the realm of what Dr. Haldane calls “conscious behaviour” the
older mechanistic outlook failed to provide the foundations of a
comprehensive interpretation of the Nature of Life. It left Man as the
peculiar province of that diffuse type of discussion which draws its
sustenance from the abstract noun and comes to fruition as magical
gesture. It should occasion no surprise that the new horizon revealed
by the growth of biological enquiry now seems contrary to common
sense and inconsistent with the language we are accustomed to use in
everyday life. Man has existed on this planet for perhaps a matter
of five hundred thousand years. During that period little more than
five thousand years have been occupied by the building of civilized
society. Of that fraction the main development of the essentially
social language of science has been compressed to a very large extent
within the last five hundred years. We are still the creatures of a
tradition of fear, of superstition and of misunderstanding, of childish
self-assertion and savage self-submissiveness to magical prohibitions
handed down to us from what Professor Levy has aptly called the
unsavoury past.
The majority of men are impatient towards the discipline which science
imposes upon us. That impatience is a bulwark of magical beliefs. It
has been well said by Trotter: “In matters that really interest him,
man cannot support the suspense of judgment which science so often has
to enjoin. He is too anxious to feel certain to have time to know.
So that we see of the sciences, mathematics appearing first, then
astronomy, then physics, then chemistry, then biology.” Because science
does not flatter our self-importance, because science makes stringent
demands on our willingness to face uncomfortable views about the
universe, because patience with the slow advance of science requires
the effort of intellectual self-renunciation, human nature, deeply
rooted in its unsavoury past, is on the side of vitalistic theories.
Social privilege is repelled by the mechanistic outlook because of its
ethical impartiality. Age brings its impressive authority to reinforce
both human nature and social privilege. When the spirit of intellectual
adventure dies and with it the courage to face the austere neutrality
of a universe which mocks the self-importance of our individual lives,
when the ruthlessness of death and decay threatens to rob us of the
few circumstances propitious to personal comfort, when the limitations
of our greatest achievements are no longer assuaged by the prospect
of renewed opportunities, it becomes all too easy to find the formula
which provides a compromise for the conflicting claims of magic and
science. Perhaps the time will come when our knowledge of the Nature of
Life will provide an explanation of this circumstance.
FOOTNOTES
[1] An examination of the precise significance of this adjective is
undertaken in the essay on the Nature of Life, p. 80 et seq.
[2] That a volley of afferent nerve impulses passes along the vagus
nerve to the brain at each heart beat is a fact which can be physically
demonstrated with the Einthoven galvanometer.
[3] British Association 1929, Section D.
[4] Professor Wildon Carr, in defending the vitalistic standpoint,
explicitly states this, as quoted in a later essay.
[5] I refer to the Uniformitarian doctrine.
[6] This objection does not apply to the use of the word mutation in
its strictly etymological connotation as a process in contradistinction
to a type.
[7] Two quotations from his writings may be added to justify the
foregoing criticism of Weismann. Concerning the essentially creative
rôle of Natural Selection he wrote, “The transformation of a species
as well as the preservation of its constancy are based upon natural
selection, and this is incessantly at work, never ceasing for a
moment.” (_Germ Plasm_, p. 414.)
Elsewhere he states that heredity and variation are coextensive. “We
have seen that this transmission affects the whole organism, and
extends to the most trifling details, and we also know that it is never
complete, and that the offspring and parent are never identical, but
that the former always differs more or less from the latter. These
differences give rise to the phenomenon of _variation, which thus
forms an integral part of heredity, for the latter always includes the
former_.” (_The Germ Plasm_, p. 410.)
[8] _The Bases of Modern Science_, pp. 234-5.
[9] _The Bases of Modern Science_, pp. 234-5.
[10] _Science and the Modern World_, pp. 255-6.
Transcriber’s Note: “{sic}” in the text is the transcriber’s. Simple
cases of typographical error have been silently corrected. Some sections
numbered “§1” were not present at chapter beginnings in the original,
and have been added in order to standardize the hierarchy of headings.
The book cover image that accompanies some ebook formats is original
and placed in the public domain.
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