หน้าหลัก Biology, History, and Natural Philosophy: Based on the Second International Colloquium held at the University..

Biology, History, and Natural Philosophy: Based on the Second International Colloquium held at the University of Denver

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In a world that peers over the brink of disaster more often than not it is difficul t to find specific assignments for the scholarly community. One speaks of peace and brotherhood only to realize that for many the only real hope of making a contribution may seem to be in a field of scientific specialization seemingly irrelevant to social causes and problems. Yet the history of man since the beginnings of science in the days of the Greeks does not support this gloomy thesis. Time and again we have seen science precipitate social trends or changes in the humanistic beliefs that have a significant effect on. the scientific community. Not infrequently the theoretical scientist, triggered by society's changing goals and understandings, finds ultimate satisfaction in the work of his colleagues in engineering and the other applied fields. Thus the major debate in mid-nineteenth century in which the evidence of natural history and geology at variance with the Biblical feats provided not only courage to a timid Darwin but the kind of audience that was needed to fit his theories into the broad public dialogue on these topics. The impact of "Darwinism" was felt far beyond the scientific community. It affected social thought, upset religious certainties and greatly affected the teaching of science.

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ISBN 10: 0-306-30573-9
ISBN 13: 978-1-4684-1965-8
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Biology, History, and Natural Philosophy

Francisco J. Ayala
Ludwig von Bertalanffy
Jay Boyd Best
Allen D. Breck
Ronald R. Cowden
Walter M. Elsasser
Constantine J. Falliers
Martin A. Garstens
Mirko D. Grmek
Stephen Korner
Arne Naess
Robert E. Roeder
Henryk Skolimowski
George Ledyard Stebbins
Albert Szent-Gyorgyi
Rene Taton
Hiikan Tornebohm
Hayden V. White
John O. Wisdom
Harry Woolf
Wolfgang Yourgrau

Biology ~ History ~ and
Natural Philosophy
Based on the
Second International Colloquium
held at the University of Denver

Edited by
Allen D. Breck
an d
Wolfgang Yourgrau
University of Denver
Denver, Colorado


The Second International Colloquium
was held at the University of Denver
November 27 - December 2, 1967

ISBN-l3: 978-1-4684-1%7-2

e-ISBN-13: 978-1-4684-1965-8

DOl: 10.1007/ 978-1-4684-1965-8
Library of Congress Catalog Card Number 70-186262
ISBN 0-306-30573-9
© 1972 Plenum Press, New York

Softcover reprint of the hardcover 1st edition 1972
A Division of Plenum Publishing Corporation
227 West 17th Street, New York, N.Y. 10011
United Kingdom edition published by Plenum Press, London
A Division of Plenum Publishing Company, Ltd.
Davis House (4th Floor), 8 Scrubs Lane, Hariesden, London
NWI0 6SE, England
All rights reserved
No part of this publication may be reproduced in any form without
written permission from the publisher

This volume is dedicated
with esteem and admiration to

Albert Szent-Gyorgyi

In a world that peers over the brink of disaster more often than not it is
difficul t to find specific assignments for the scholarly community. One speaks
of peace and brotherhood only to realize that for many the only real hope of
making a contribution may seem to be in a field of scientific specialization
seemingly irrelevant to social causes and problems.
Yet the history of man since the beginnings of science in the days of the
Greeks does not support this gloomy thesis. Time and again we have seen
science precipitate social trends or changes in the humanistic beliefs that have
a significant effect on. the scientific community. Not infrequently the
theoretical scientist, triggered by society's changing goals and understandings,
finds ultimate satisfaction in the work of his colleagues in engineering and the
other applied fields.
Thus the major debate in mid-nineteenth century in which the evidence
of natural history and geology at variance with the Biblical feats provided not
only courage to a timid Darwin but the kind of audience that was needed to
fit his theories into the broad public dialogue on these topics. The impact of
"Darwinism" was felt far beyond the scientific community. It affected social
thought, upset religious certainties and greatly affected the teaching of
We could find many other such examples. They lend hope to the belief
that there is great worth in bringing together scientists and scholars in other
fields for colloquia such as the one whose proceedings make up the main
body of this book. In the presence of the philosopher of science, the pure
researcher, the historian-in the community of minds and skills that is the
very essence of a present and future world-one must hope that the past will
repeat itself and new understandings, adequate to our needs and our times,
will be the result.
That this could happen at all, here in the foothills of the great Rocky
Mountain range, is one of those minor miracles of determination, organization
and support that seem to occur less frequently today than a decade or two
ago. Thanks are very much in order, and should be addressed first to the
scholars who came to the University of Denver from far places and always at
the expense of other work and other demands on their time and skills.



We also owe a vote of thanks to the Martin-Marietta Corporation for their
contribution of funds and enthusiasm, which made this and its predecessor
Colloquium possible. The proximity of one of their major installations to the
University of Denver and the common interest which pervades their research
and ours have always provided a close bond in the development of solutions
beneficial to the future.
In the deepening sea of troubles which surround us many pray for
another Renaissance, a rediscovery "of man and of nature" with its roots, as
before, in classical thought and humanistic involvement in scientific ways of
thought. Just as the turmoil and new ideas of the Renaissance had their roots
in all that had gone before, so may another turning point in history rest on
the foundations of scientific discovery and social awareness of the century
now nearing its close. The great hope that this might indeed come to pass
may well be our willingness to keep the talk going, to share ideas, to take the
time from our specialized fields to try to understand both the men and the
ideas that exist in other private and little-known realms. To do this in the
natural sciences seems one of the highest orders of priority, and the usefulness
of the effort may be estimated after one has read the pages that follow.
Since I am already convinced that we have done a most useful thing in
holding and publishing this Colloquium, I can only close by expressing the
hope that many of us will meet again one day on another such occasion.
University of Denver
Denver, Colorado
November, 1971

Maurice B. Mitchell

The First International Colloquium on Physics, Logic, and History held at
the University of Denver in May 1966, produced a scholarly volume of papers
and comments; it was published in 1970 by the Plenum Press, New York. The
success of that conference and the predictable response to the diverse papers
and their discussions emboldened its organizers to gather another distinguished
group of thinkers for a second Colloquium in the fall of 1967. The results of
that conference are collected in this volume.
Again, it was our hope to contribute to some kind of understanding
among academic disciplines only too often thought to be quite separated in
purpose, formulation, and intrinsic technique. It is one of the most tragic
difficulties of our time that scientists, historians, and philosophers have failed
to listen to each other. The inevitable and dramatic advance in the various
aspects of systematic knowledge has, unfortunately, led to an almost cavalier
disregard for those aspects or elements essential to all pursuits of knowledge
based on intelligible communication.
Thinkers like Nietzsche, whose anti-scientific attitude is proverbial, stated
shortly before his mind deteriorated in the quicksand.of mental disease, that
he would like to study biology in a systematic manner and he even flirted
with the idea of enrolling as a student of this subject. He recognized, as one
among the first so-called non-scientific thinkers, that a deeper insight into the
biological sciences may be imperative for his philosophy of life, which had
been based entirely upon his intensive study of the Greek classics and some
subjective philosophic ideas in general.
This second Symposium places the biological sciences at the center of our
attention, flanked by some excursions into history and an occasional journey
into natural philosophy. When we decided upon the issues which were
supposed to be considered, we intended to explore topics like: "Is biology an
autonomous science?"; "'Organisms have been likened to machines' -is this
assertion true?"; "Schrodinger and Teilhard de Chardin-two controversial
credos in contemporary biological sciences"; "Historical systems considered
from a biological point of view," etc.
The diverse papers and the ensuing discussions among biologists, historians
and philosophers, historians and philosophers of science, are here presented



because we were guided by the possibility that the search for a comprehensive
understanding of nature may be pursued along a broader spectrum of
knowledge by means of objective investigation, discussion, and hopefully
It should be noted that the lectures contained in this volume do not
correspond exactly with those given at the Conference. In a few cases authors
requested permission to withdraw their papers rather than see them in print.
All contributors were given a chance to make such revisions as would bring
their conclusions up to date when new discoveries were made in their
respective fields or further reflection altered some aspects of their views. But,
the most fruitful contribution of the Colloquium resulted from informal
discussions of the participants and interested observers.
In one important way, however, this volume differs from its predecessor.
The editors thought best to omit the lengthy discussions which followed each
paper. The difficulties of transcription, the incredibly vexing problem of
editing remarks which were later amplified or discarded, the many ad
hominem comments-all this made such inclusion less commendable for this
specific collection of essays.
Some scholars who had been invited to participate were unfortunately
unable to join us. They have been none the less gracious enough to send
copies of their papers so they might become a part of this presentation.
Special thanks of the editors go to Dr. Maurice B. Mitchell, Chancellor of the
University of Denver, for presiding over some of the sessions and for
participating from the beginning in making the Colloquium possible. Dr.
Edward A. Lindell, Dean of the College of Arts and Sciences, was
indispensable in helping to plan the format, complete arrangements for
bringing participants to the campus, and carry out the multitudinous details
without which the Symposium could never have materialized. The organizing
committee consisted of Dr. Breck, Dr. Lindell, and Dr. Yourgrau.
This second Colloquium (as well as the first) was made possible by a
grant from the Martin-Marietta Corporation Foundation and further financial
support by the University of Denver. The entire manuscript was typed
several times by Mrs. Betty Greenwell, secretary of the program in the
history and philosophy of science. For all her tireless efforts we are indeed
most grateful.
University of Denver
Denver, Colorado
September, 1971

The Editors

FRANCISCO J. AYALA, The Rockefeller University, New York, New York
SAUL BENISON, University of Cincinnati, Cincinnati, Ohio
LUDWIG VON BERTALANFFY, State University of New York at Buffalo,
Buffalo, New York
JAY BOYD BEST, Colorado State University, Fort Collins, Colorado
ALLEN D. BRECK, University of Denver, Denver, Colorado
WILLIAM T. DRISCOLL University of Denver, Denver, Colorado
WALTER M. ELSASSER, University of Maryland, College Park, Maryland
CONSTANTINE J. FALLIERS, Children's Asthma Research Institute, Denver,
GEORGE GAMOW, University of Colorado, Boulder, Colorado
MARTIN A. GARSTENS, University of Maryland and the Office of Naval
Research, College Park, Maryland
MIRKO D. GRMEK, Archives Internationales d'Historie des Sciences, Paris,
STEPHAN KORNER, University of Bristol, England
EDWARD J. MACHLE, University of Colorado, Boulder, Colorado
ARNES NAESS, University of Oslo, Norway
JOHN R. OLIVE, American Institute of Biological Sciences, Washington, D.C.
THEODORE T. PUCK, University of Colorado School of Medicine, Denver,
ROBERT E. ROEDER, University of Denver, Denver, Colorado
HARRY ROSENBERG, Colorado State University, Fort Collins, Colorado
GEORGE G. SIMPSON University of Arizona, Tucson, Arizona
HENRYK SKOLIMOWSKI, University of Southern California, Los Angeles,



ALBERT SZENT-GYORGYI, Laboratory of the Institute of Muscle Research,
Marine Biological Laboratory, Woods Hole, Massachusetts
RENE TATON, Ecole Pratique des Hautes Etude, Paris, France
HAKAN TORNEBOHM, University of Goteborg, Sweden
STANISLAW M. ULAM, University of Colorado, Boulder, Colorado
HA YDEN V. WHITE University of California, Los Angeles, California
JOHN O. WISDOM, York University, Toronto, Canada
HARRY WOOLF, The Johns Hopkins University, Baltimore, Maryland
WOLFGANG YOURGRAU, University of Denver, Denver, Colorado










Maurice B. Mitchell, Chancellor, University of Denver
The Editors
Francisco J. Ayala, The Rockefeller University ................ .
BIOLOGY, Ludwig von Bertalanffy, State University of
New York at Buffalo .................................... 17
Albert Szent-Gybrgyi, Marine Biological Laboratory,
Woods Hole, Massachusetts ............................... 31
State University, Fort Collins ............................. 37
TEMPLATES, George Ledyard Stebbins, University of
California, Davis ........................................ 79
DEVELOPMENT, Ronald R. Cowden, University of Denver .... 103
Constantine J. Falliers, Children's Asthma Research Institute
& Hospital, Denver ..................................... III
University of Maryland and the Office of Naval Research ...... 123
THEORETICAL BIOLOGY, Walter M. Elsasser, University of
Maryland ............................................ 135
OF VIEW, H3.kan T6rnebohm, University of Gdteborg



Rene Taton, Ecole Pratique des Hautes Etude, Paris ..........
DESCARTES, Mirko D. Grmek, Archives Internationales
d 'Historie des Sciences, Paris .............................
CHARDIN, Francisco J. Ayala, The Rockefeller University .....
OF HISTORY, Allen D. Breck, University of Denver ..........
University of California, Los Angeles ......................
AND HISTORY, Stephan Korner, University of Bristol ........
XVIII. HISTORICAL TAXONOMY, Robert E. Roeder, University
of Denver .•..........................................
CENTURY, Harry Woolf, The Johns Hopkins University .......
York University .......................................
Henryk Skolimowski, University of Southern California ........
University of Denver ...................................
INDEX ....................................................






The Autonomy of Biology as a
Natural Seienee
Francisco J. Ayala
The Rockefeller University

The goal of science is the systematic organization of knowledge about the
material universe on the basis of explanatory principles that are genuinely
testable. The starting point of science is the formulation of statements about
objectively observable phenomena. Common-sense knowledge also provides
information about the material world. The distinction between science and
common-sense knowledge is based upon the joint presence in science of at
least three distinctive characteristics. First, science seeks to organize knowledge in a systematic way by exhibiting patterns of relations among statements
concerning facts which may not obviously appear as mutually related.
The information obtained in the course of ordinary experience about the
material universe is frequently accurate, but it seldom provides any explanation of why the facts are as alleged. It is the second distinctive characteristic
of science that it strives to provide explanations of why the observed events
do in fact occur. Science attempts to discover and to formulate the conditions
under which the observed facts and their mutual relationships exist.
Thirdly, the explanatory hypotheses provided by science must be
genuinely testable, and therefore subject to the possibility of rejection. It is
sometimes asserted that scientific explanatory hypotheses should allow to
formulate predictions about their subject matter which can be verified by
further observation and experiment. However, in certain fields of scientific
knowledge, like in those fields concerned with historical questions, prediction
is considerably restricted by the nature of the subject matter itself. The
criterion of testability can then be satisfied by requiring that scientific
explanations have precise logical consequences which can be verified or
falsified by observation and experiment. The word "precise" is essential in the
previous sentence. To provide genuine verification the logical consequences of
the proposed explanatory hypotheses must not be compatible with alternate


Biology, History and Natural Philosophy

It is the concern of science to formulate theories, that is, to discover
patterns of relations among vast kinds of phenomena in such a way that a
small number of principles can explain a large number of propositions
concerning these phenomena. In fact, science develops by discovering new
relationships which show that observational statements and theories that had
hitherto appeared as independent are in fact connected and can be integrated
into a more comprehensive theory. Thus, the Mendelian principles of
inheritance can explain, about many different kinds of organisms, observations
which appear as prima facie unrelated; like the proportions in which
characters are transmitted from parents to offspring, the discontinuous nature
of many traits of organisms, and why in out breeding sexual organisms not two
individuals are likely to be genetically identical even when the number of
individuals in the species is very large. Knowledge about the formation of the sex
cells and about the behavior of chromosomes was eventually shown to be
connected with the Mendelian principles, and contributed to explain additional
facts; like why certain traits are inherited independently from each other while
other traits are transmitted together more frequently than not. Additional
discoveries have contributed to the formulation of a unified theory of
inheritance which explains many other diverse observations, including the
distinctiveness of natural species, the adaptive nature of organisms and their
features, and paleontological observations concerning the evolution of
The connection among theories has sometimes been established by showing
that the principles of a certain theory or branch of science can be explained
by the principles of another theory or science shown to have greater
generality. The less general branch of science, called the secondary science, is
said to have been reduced to the more general or primary science. A typical
example is the reduction of Thermodynamics to Statistical Mechanics. 1 The
reduction of one branch of science to another simplifies and unifies science.
Reduction of one theory or branch of science to another has repeatedly
occurred in the history of science. During the last hundred years several
branches of Physics and Astronomy have been to a considerable extent unified
by their reduction to a few theories of great generality like Quantum
Mechanics and Relativity. A large sector of Chemistry has been reduced to
Physics after it was discovered that the valence of an element bears a simple
relation to the number of electrons in the outer orbit of the atom. The
impressive success of these and other reductions has led in certain circles to
the conviction that the ideal of science is to reduce all natural sciences,
including biology, to a comprehensive theory that will provide a common set
of principles of maximum generality capable of explaining all our observations
about the material universe.
To evaluate the validity of such claims, I will briefly examine some of the
necessary conditions for the reduction of one theory to another. I will, then,

The Autonomy of Biology as a Natural Science


attempt to show that at the present stage of development of the two sciences,
the reduction of biology to physics cannot be effected. I will further claim, in
the second part of this paper, that there are patterns of explanation which are
indispensable in biology while they do not occur in the physical sciences.
These are teleological explanations which apply to organisms and only to
them in the natural world, and that cannot be reformulated in non teleological
form without loss of explanatory content.
Conditions for Reduction

In general, reduction can be defined in the present context as "the
explanation of a theory or a set of experimental laws established in an area of
inquiry, by a theory usually though not invariably formulated for some other
domain."2 Nagel has stated the two formal conditions that must be satisfied
to effect the reduction of one science to another. First, all the experimental
laws and theories of the secondary science must be shown to be logical
consequences of the theoretical constructs of the primary science. This has
been called by Nagel the condition of derivability.
Generally, the experimental laws formulated in a certain branch of science
will contain terms which are specific to that area of inquiry. If the laws of the
secondary science contain some terms that do not occur in the primary
science, logical derivation of its laws from the primary science will not be
prima facie possible. No term can appear in the conclusion of a formal
demonstration unless the term appears also in the premisses. To make
reduction possible it is then necessary to establish suitable connections
between the terms of the secondary science and those used in the primary
science. This may be called the condition of connectability. It can be satisfied
by a redefinition of the terms of the secondary science using terms of the
primary science. For example, to effect the reduction of genetics to physical
science such concepts as gene, chromosome, etc., must be redefined in
physicochemical terms such as atom, molecule, electrical charge, hydrogen
bond, deoxyribonucleic acid, length, etc.
The problem of reduction is sometimes formulated as whether the
properties of a certain kind of objects, for instance organisms, can be
explained as a function of the properties of another such group of objects, like
the organism's physical components organized in certain ways. This formulation of the question is spurious and cannot lead to a satisfactory answer.
Indeed it is not clear what is meant by the "properties" of a certain object
which enters as a part or component of some other object. If all the
properties are included, it appears that reduction can always be accomplished,
and it is in fact a trivial issue. Among the properties of a certain object one
will list the properties which it has when it is a component of the larger
whole. To use a simple example, one may list among the properties of


Biology, History and Natural Philosophy

hydrogen that of combining in a certain way with oxygen to form water, a
substance which possesses certain specified properties. The properties of water
will then be included among the properties of oxygen and hydrogen.
The reduction of one science to another is not a matter of deriving the
properties of a kind of objects from the properties of some other group of
objects. It is rather a matter of deriving a set of propositions from another
such set. It is a question about the possibility of deriving the experimental
laws of the secondary science as the logical consequences of the theoretical
laws of the primary science. Scientific laws and theories consist of propositions about the material world, and the question of reduction can only be
settled by the concrete investigation of the logical consequences of such
propositions, and not by discussion of the properties or the natures of things.
From the previous observation it follows that the question of reduction
can only be solved by a specific reference to the actual stage of development
of the two disciplines involved. Certain parts of chemistry were reduced to
physics after the modern theories of atomic structure was developed some
fifty years ago, but the reduction could not have been accomplished before
such development. If the reduction of one science to another is not possible
at the present stage of development of the two disciplines, it is empirically
meaningless to ask whether reduction will be possible at some further time,
since the question can only be answered dogmatically or in terms of
metaphysical preconceptions.
Simpson has suggested that the unification of the various natural sciences
be sought not "through principles that apply to all phenomena but through
phenomena to which all principles apply." Science, according to Simpson, can
truly become unified in biology, since the principles of all natural sciences can
be applied to the phenomena of life. 3 To be sure, the theoretical laws of
physics and chemistry apply to the physicochemical phenomena occurring in
organisms. Besides, there are biological theories that explain observations
concerning the living world but have no application to nonliving matter. To
conclude that therefore biology stands at the center of all science is true as
far as it goes, but it is trivial and provides no progress in scientific
understanding that I can discern.
The goal of the reductionistic program is not, as Simpson seems to
believe, to establish a "body of theory that might ultimately be completely
general in the sense of applying to all material phenomena," nor a "search for
a least common denominator in science." It is rather a quest for a
comprehensive theory that would explain all material phenomena-the living as
well as the inanimate world-with an economy of stated laws and a
corresponding increase in our understanding of the world. Whether such an
ideal can be accomplished is a different issue that I shall consider presently.

The Autonomy of Biology as a Natural Science


The Reduction of Biology to Physical Science

The question of the reducibility of biology to physicochemistry has been
raised again in the last decade particularly in connection with the spectacular
successes accomplished in certain areas of biology. In genetics, research at the
molecular level has contributed to establish the chemical structure of the
hereditary material, to decipher the genetic code, and to provide some
understanding of the mechanisms of gene action. Brilliant achievements have
also been obtained in neurophysiology and other fields of biology. Some
authors have claimed that the understanding of all biological phenomena in
physicochemical terms is not only possible but the task of the immediate
future. It is thus proclaimed that the only worthy and truly "scientific"
biological research is what is called in recent jargon "molecular biology," that
is the attempt to explain biological phenomena in terms of the underlying
physicochemical components and processes.
I will without much ado dispose of two extreme positions which seem
equally unprofitable. On one end of the spectrum there are substantive
vitalists which defend the irreducibility of biology to physical science because
living phenomena are the effect of a nonmaterial principle which is variously
called vital force, entelechy, elan vital, radial energy, or the like. A
nonmaterial principle cannot be subject to scientific observation nor lead to
genuinely testable scientific hypotheses. 4
At the other end of the spectrum stand those who claim that reduction
of biology to physicochemistry is in fact possible at present. At the current
stage of scientific development, a majority of biological concepts, like cell,
organ, species, ecosystem, etc., cannot be formulated in physicochemical
terms. Nor is there at present any class of statements belonging to physics and
chemistry from which every biological law could be logically derived. In other
words, neither the condition of connectability nor the condition of derivability-two necessary formal conditions of reduction-are satisfied at the present
stage of development of physical and biological knowledge.
Two intermediate positions have also appeared in the recent literature.
The reductionist position maintains that although the reduction of biology to
physics cannot be effected at present, it is possible in principle. The factual
reduction is made contingent upon further progress in the biological or in the
physical sciences, or in both. Certain antireductionist authors claim that
reduction is not possible in principle because organisms are not merely
assemblages of atoms and molecules, nor even of organs and tissues standing
in merely external relation to one another. Organisms are alleged to be
"wholes" that must be studied as wholes and not as the "sum" of isolable
parts. s
Although biological laws are not in general derivable from any available
theory of physics and chemistry, the reductionists claim that such


Biology, History and Natural Philosophy

accomplishment will be possible in the future. Such proposition is frequently
based on metaphysical preconceptions about the nature of the material world.
It cannot be in any case convincingly argued empirically, since it is only a
statement of faith about the possibility of some future event. It must be
noted, however, that advances in various areas of molecular biology are
continuously extending the as yet exiguous realm of biological phenomena
that can be explained in terms of physicochemical concepts and laws.
As for the antireductionist position that maintains that organisms and
their properties cannot be understood as mere "sums" of their parts, I have
already stated that it rests on an unsatisfactory formulation of the problem.
The question of reduction is whether propositions concerning organisms can
be logically derived from physicochemical laws, and not whether the
properties of organisms can be explained as the result of the properties of
their physical components. It should perhaps be added that the phenomenon
of so-called "emergent" properties occurs also in the nonliving world. Water is
formed by the union of two atoms of hydrogen with one atom of oxygen,
but water exhibits properties which are not the immediately apparent
consequence of the properties of the two gases, hydrogen and oxygen.
Another simple example can be taken from the field of thermodynamics. A
gas has a temperature although the individual molecules of the gas cannot be
said to possess a temperature. 6
The reduction of biology to physicochemistry cannot be effected at the
present stage of scientific knowledge. Whether the reduction will be possible
in the future is an empirically meaningless question. A majority of biological
problems cannot be as yet approached at the molecular level. Biological
research must then continue at the different levels of integration of the living
world, according to the laws and theories developed for each order of
complexity. The study of the molecular structure of organisms must be
accompanied by research at the levels of the cell, the organ, the individual,
the population, the species, the community, and the ecosystem. These levels
of integration are not independent of each other. Laws formulated at one
level of complexity illuminate the other levels, both lower and higher, and
suggest additional research strategies. 7 It is perhaps worth pointing out that in
fact biological laws discovered at a higher level of organization have more
frequently contributed to guide research at the lower level than vice versa. To
mention but one example, the Mendelian theory of inheritance preceded the
identification of the chemical composition and structure of the genetic
material and made possible such discoveries.
The Notion of Teleology

I will now proceed to discuss the role of teleological explanations in
biology. I shall attempt to show that teleological explanations constitute

The Autonomy of Biology as a Natural Science


patterns of explanation that apply to organisms while they do not apply to
any other kind of objects in the natural world. I shall further claim that
although teleological explanations are compatible with causal accounts they
cannot be reformulated in nonteleological form without loss of explanatory
content. Consequently, I shall conclude that teleological explanations cannot
be dispensed with in biology, and are therefore distinctive of biology as a
natural science.
The concept of teleology is in general disrepute in modern science. More
frequently than not it is considered to be a mark of superstition, or at least a
vestige of the nonempirical, a prioristic approach to natural phenomena
characteristic of the pre scientific era. The main reason for this discredit is that
the notion of teleology is equated with the belief that future events-the goals
or end-products of processes-are active agents in their own realization. In
evolutionary biology, teleological explanations are understood to imply the
belief that there is a planning agent external to the world, or a force
immanent to the organisms, directing the evolutionary process toward the
production of specified kinds of organisms. The nature and diversity of
organisms are, then, explained teleologically in such view as the goals or
ends-in-view intended from the beginning by the Creator, or implicit in the
nature of the first organisms.
Biological evolution can be explained without recourse to a Creator or
planning agent external to the organisms themselves. There is no evidence
either of any vital force or immanent energy directing the evolutionary
process toward the production of specified kinds of organisms. The evidence
of the fossil record is against any necessitating force, external or immanent,
leading the evolutionary process toward specified goals. Teleology in the
stated sense is, then, appropriately rejected in biology as a category of
In The Origin of Species Darwin accumulated an impressive number
of observations supporting the evolutionary origin of living organisms.
Moreover, and perhaps most importantly, he provided a causal explanation of
evolutionary processes-the theory of natural selection. The principle of
natural selection makes it possible to give a natural explanation of the
adaptation of organisms to their environments. Darwin recognized, and
accepted without reservation, that organisms are adapted to their environments, and that their parts are adapted to the functions they serve. Penguins
are adapted to live in the cold, the wings of birds are made to fly, and the
eye is made to see. Darwin accepted the facts of adaptation, and then
provided a natural explanation for the facts. One of his greatest accomplishments was to bring the teleological aspects of nature into the realm of science.
He substituted a scientific teleology for a theological one. The teleology of
nature could now be explained, at least in principle, as the result of natural


Biology, History and Natural Philosophy

laws manifested in natural processes, without recourse to an external Creator
or to spiritual or nonmaterial forces. At that point biology came into maturity
as a science.
The concept of teleology can be defined without implying that future
events are active agents in their own realization nor that the end-results of a
process are consciously intended as goals. The notion of teleology arose most
probably as a result of man's reflection on the circumstances connected with
his own voluntary actions. The anticipated outcome of his actions can be
envisaged by man as the goal or purpose toward which he directs his activity.
Human actions can be said to be purposeful when they are intentionally
directed toward the obtention of a goal.
The plan or purpose of the human agent may frequently be inferred from
the actions he performs. That is, his actions can be seen to be purposefully or
teleologically ordained toward the obtention of a goal. In this sense the
concept of teleology can be extended, and has been extended, to describe
actions, objects or processes which exhibit an orientation toward a certain
goal or end-state. No requirement is necessarily implied that the objects or
processes tend consciously toward their specified end-states, nor that there is
any external agent directing the process or the object toward its end-state or
goal. In this generic sense, teleological explanations are those explanations
where the presence of an object or a process in a system is explained by
exhibiting its connection with a specific state or property of the system to
whose existence or maintenance the object or process contributes. Teleological
explanations require that the object or process contribute to the existence of
a certain state or property of the system. Moreover, and this is the essential
component of the concept, teleological explanations imply that such contribution is the explanatory reason for the presence of the process or object in the
system. Accordingly, it is appropriate to give a teleological explanation of the
operation of the kidney in regulating the concentration of salt in the blood,
or of the structure of the hand of man obviously adapted for grasping. But it
makes no sense to explain teleologically the motions of a planet or a chemical
reaction. In general, as it will be shown presently, teleological explanations are
appropriate to account for the existence of adaptations in organisms while
they are neither necessary nor appropriate in the realm of nonliving matter.
There are at least three categories of biological phenomena where
teleological explanations are appropriate, although the distinction between the
categories need not always be clearly defined. These three classes of
teleological phenomena are established according to the mode of relationship
between the structure or process and the property or end-state that accounts
for its presence. Other classifications of teleological phenomena are possible
according to other principles of distinction. A second classification will be
suggested later.

The Autonomy of Biology as a Natural Science


(1) When the end-state or goal is consciously anticipated by the agent.
This is purposeful activity and it occurs in man and probably, although in a
lesser degree, in other animals. I am acting teleologically when I buy an
airplane ticket to fly to Mexico City. A cheetah hunting a zebra has at least
the appearance of purposeful behavior. However, as I have said above, there is
no need to explain the existence of organisms and their adaptations as the
result of the consciously intended activity of a Creator. There is purposeful
activity in the living world, at least in man; but the existence of the living
world, including man, need not be explained as the result of purposeful
behavior. When some critics reject the notion of teleology from the natural
sciences, they are considering exclusively this category of teleology.
(2) Self-regulating or teleonomic systems, when there exists a mechanism
that enables the system to reach or to maintain a specific property in spite of
environmental fluctuations. The regulation of body temperature in mammals is
a teleological mechanism of this kind. In general, the homeostatic reactions of
organisms belong to this category of teleological phenomena. Two types of
homeostasis are usually distinguished by biologists-physiological and developmental homeostasis, although intermediate and additional types do exist. 8
Physiological homeostatic reactions enable the organism to maintain certain
physiological steady states in spite of environmental shocks. The regulation of
the composition of the blood by the kidneys, or the hypertrophy of muscle in
case of strenuous use, are examples of this type of homeostasis.
Developmental homeostasis refers to the regulation of the different paths
that an organism may follow in its progression from zygote to adult. The
development of a chicken from an egg is a typical example of developmental
homeostasis. The process can be influenced by the environment in various
ways, but the characteristics of the adult individual, at least within a certain
range, are largely predetermined in the fertilized egg. Aristotle, Saint
Augustine, and other ancient and mediaeval philosophers, took developmental
homeostasis as the paradigm of all teleological mechanisms. According to Saint
Augustine, God did not create directly all living species of organisms, but these
were implicit in the primeval forms created by God. The existing species arose
by a natural "unfolding" of the potentialities implicit in the primeval forms or
"seeds" created by God.
Self-regulating systems or servo-mechanisms built by man belong in this
second category of teleological phenomena. A simple example of such
servo-mechanisms is a thermostat unit that maintains a specified room
temperature by turning on and off the source of heat. Self-regulating
mechanisms of this kind, living or man-made, are controlled by a feed-back
system of information.
(3) Structures anatomically and physiologically constituted to perform a
certain function. The hand of man is made for grasping, and his eye for


Biology. History and Natural Philosophy

VISIOn. Tools and certain types of machines made by man are teleological in
this third sense. A watch, for instance, is made to tell time, and a fawcet to
draw water. The distinction between the (3) and (2) categories of teleological
systems is sometimes blurred. Thus the human eye is able to regulate itself
within a certain range to the conditions of brightness and distance so as to
perform its function more effectively.
Teleology and Adaptation

Teleological mechanisms and structures in organisms are biological
adaptations. They have arisen as a result of the process of natural selection.
Natural selection is a mechanistic process defined in genetic and statistical
terms as differential reproduction. Some genes and genetic combinations are
transmitted to the following generations on the average more frequently than
their alternates. Such genetic units will become more common, and their
alternates less common, in every subsequent generation.
The genetic variants arise by the random processes of genetic mutation
and recombination. Genetic variants increase in frequency and may eventually
become fixed in the popUlation if they happen to be advantageous as
adaptations in the organisms which carry them, since such organisms are likely
to leave more descendants than those lacking such variants. If a genetic variant
is harmful or less adaptive than its alternates, it will be eliminated from the
population. The biological adaptations of the organisms to their environments
are, then, the result of natural selection, which is nevertheless a mechanistic
and impersonal process.
The adaptations of organisms-whether organs, homeostatic mechanisms,
or patterns of behavior-are explained teleologically in that their existence is
ultimately accounted for in terms of their contribution to the reproductive
fitness of the species. A feature of an organism that increases its reproductive
fitness will be selectively favored. Given enough generations it will extend to
all the members of the population.
Patterns of behavior, such as the migratory habits of certain birds or the
web-spinning or spiders, have developed because they favored the reproductive
success of their possessors in the environments where the population lived.
Similarly, natural selection can account for the existence of homeostatic
mechanisms. Some living processes can be operative only within a certain
range of conditions. If the environmental conditions oscillate frequently
beyond the functional range of the process, natural selection will favor
self-regulating mechanisms that maintain the system within the functional
range. In man death results if the body temperature is allowed to rise or fall
by more than a few degrees above or below normal. Body temperature is
regulated by dissipating heat in warm environments through perspiration and
dilation of the blood vessels in the skin. In cool weather the loss of heat is

The Autonomy of Biology as a Natural Science


minimized, and additional heat is produced by increased activity and shivering.
Finally, the adaptation of an organ or structure to its function is also
explained teleolOgically in that its presence is accounted for in terms of the
contribution it makes to reproductive success in the population. The
vertebrate eye arose because genetic mutations responsible for its development
occurred which increased the reproductive fitness of their possessors.
There are in all organisms two levels of teleology that may be labelled
specific and generic. There usually exists a specific and proximate end for
every feature or an animal or plant. The existence of the feature is explained
in terms of the function or property that it serves. This function or property
can be said to be the specific or proximate end of the feature. There is also
an ultimate goal to which all features contribute or have contributed in the
past-reproductive success. The generic or ultimate end to which all features
and their functions contribute is increased reproductive efficiency. The
presence of the functions themselves-and therefore of the features which
serve them-is ultimately explained by their contribution to the reproductive
fitness of the organisms in which they exist. In this sense the ultimate source
of explanation in biology is the principle of natural selection.
Natural selection can be said to be a teleological process in a causal sense.
Natural selection is not an entity but a purely mechanistic process. But
natural selection can be said to be teleological in the sense that it produces
and maint('ins end-directed organs and mechanisms, when the functions served
by them contribute to the reproductive efficiency of the organism.
The process of natural selection is not at all teleological in a different
sense. Natural selection does not tend in any way toward the production of
specific kinds of organisms or toward organisms having certain specific
properties. The over-all process of evolution cannot be said to be teleological
in the sense of proceeding toward certain specified goals, preconceived or not.
The only nonrandom process in evolution is natural selection understood as
differential reproduction. Natural selection is a purely mechanistic process and
it is opportunistic. 9 The final result of natural selection for any species may
be extinction, as shown by the fossil record, if the species fails to cope with
environmental change.
The presence of organs, processes and patterns of behavior can be
explained teleologically by exhibiting their contribution to the reproductive
fitness of the organisms in which they occur. This need not imply that
reproductive fitness is a consciously intended goal. Such intent must in fact be
denied, except in the case of the voluntary behavior of man. In teleological
explanations the end-state or goal is not to be understood as the efficient
cause of the object or process that it explains. The end-state is causally-and
in general temporarily also-posterior.


Biology, History and Natural Philosophy

Internal and External Teleology

Three categories of teleological phenomena have been distinguished above,
according to the nature of the relationship existing between the object or
mechanism and the function or property that it serves. Another classification
of teleology may be suggested attending to the process or agency giving origin
to the teleological system. The end-directedness of living organisms and their
features may be said to be internal teleology, while that of man-made tools
and servo-mechanisms may be called external teleology. It might also be
appropriate to refer to these two kinds of teleology as natural and artificial,
but the other two terms, "internal" and "external," have already been used. 1o
Internal teleological systems are accounted for by natural selection which
is a strictly mechanistic process. External teleological systems are the products
of the human mind, or more generally, are the result of purposeful activity
consciously intending specified ends. An automobile, a wrench and a
thermostat are teleological systems in the external sense; their parts and
mechanisms have been produced to serve certain functions intended by man.
Organisms and their parts are teleological systems in the internal sense; their
end-directedness is the result of the mechanistic process of natural selection.
Organisms are the only kind of systems exhibiting internal teleology. In fact
they are the only class of natural systems that exhibit teleology. Among the
natural sciences, then, only biology, which is the study of organisms, requires
teleology as a category of explanation.
Organisms do not in general possess external teleology. As I have said
above, the existing kinds of organisms and their properties can be explained
without recourse to a Creator or planning agent directing the evolutionary
process toward the production of such organisms. The evidence from
paleontology, genetics, and other evolutionary sciences is also against the
existence of any immanent force or vital principle directing evolution toward
the production of specified kinds of organisms.
Teleological Explanations in Biology

Teleological explanations are fully compatible with causal accounts.
"Indeed, a teleological explanation can always be transformed into a causal
one."ll Consider a typical teleological statement in biology, "The function of
gills in fishes is respiration." This statement is a telescoped argument the
content of which can be unraveled approximately as follows: Fish respire; if
fish have no gills, they do not respire; therefore fish have gills. According to
Nagel, the difference between a teleological explanation and a nonteleological
one is, then, one of emphasis rather than of asserted content. A teleological
explanation directs our attention to "the consequences for a given system of a
constituent part of process." The equivalent nonteleological formulation
focuses attention on "some of the conditions ... under which the system
persists in its characteristic organization and activities." 12

The Autonomy of Biology as a Natural Science


Although a teleological explanation can be reformulated in a nonteleological one, the teleological explanation connotes something more than the
equivalent nonteleological one. In the first place, a teleological explanation
implies that the system under consideration is directively organized. For that
reason teleological explanations are appropriate in biology and in the domain
of cybernetics but make no sense when used in the physical sciences to
describe phenomena like the fall of a stone. Teleological explanations imply,
while nonteleological ones do not, that there exists a means-to-end relationship in the systems under description.
Besides connoting that the system under consideration is directively
organized, teleological explanations also account for the existence of specific
functions in the system and more generally for the existence of the directive
organization itself. The teleological explanation accounts for the presence in
an organism of a certain feature, say the gills, because it contributes to the
performance or maintenance of a certain function, respiration. In addition it
implies that the function exists because it contributes to the reproductive
fitness of the organism. In the nonteleological translation given above, the
major premiss states that "fish respire." Such formulation assumes the
presence of a specified function, respiration, but it does not account for its
existence. The teleological explanation does in fact account for the presence
of the function itself by implying or stating explicitly that the function in
question contributes to the reproductive fitness of the organism in which it
exists. Finally, the teleological explanation gives the reason why the system is
directively organized. The apparent purposefulness of the ends-to-mean
relationship existing in organisms is a result of the process of natural selection
which favors the development of any organization that increases the
reproductive fitness of the organisms.
If the above reasoning is correct, the use of teleological explanations in
biology is not only acceptable but indeed indispensable. Organisms are systems
directively organized. Parts of organisms serve specific functions that,
generally, contribute to the ultimate end of reproductive survival. One
question biologists ask about organic structures and activities is "What for?"
That is, "What is the function or role of such a structure or such a process?"
The answer to this question must be formulated in teleological language. Only
teleological explanations connote the important fact that plants and animals
are directively organized systems.
It has been argued by some authors that the distinction between systems
that are goal directed and those which are not is highly vague. The
classification of certain systems as teleological is allegedly rather arbitrary. A
chemical buffer, an elastic solid or a pendulum at rest are examples of
physical systems that appear to be goal directed. I suggest using the criterion
of utility to determine whether an entity is teleological or not. The criterion


Biology, History and Natural Philosophy

of utility can be applied to both internal and external teleological systems.
Utility in an organism is defined in reference to the survival and reproduction
of the organism itself. A feature of a system will be teleological in the sense
of internal teleology if the feature has utility for the system in which it exists
and if such utility explains the presence of the feature in the system.
Operationally, then, a structure or process of an organism is teleological if it
can be shown to contribute to the reproductive efficiency of the organism
itself, and if such contribution accounts for the existence of the structure or
In external teleology utility is defined in reference to the author of the
system. Man-man tools or mechanisms are teleological with external teleology
if they have been designed to serve a specified purpose, which therefore
explains their existence and properties. If the criterion of utility cannot be
applied, a system is not teleological. Chemical buffers, elastic solids and a
pendulum at rest are not teleological systems.
The utility of features of organisms is with respect to the individual or
the species in which they exist at any given time. It does not include
usefulness to any other organisms. The elaborate plumage and display is a
teleological feature of the peacock because it serves the peacock in its attempt
to find a mate. The beautiful display is not teleologically directed toward
pleasing man's aesthetic sense. That it pleases the human eye is accidental,
because it does not contribute to the reproductive fitness of the peacock
(except, of course, in the case of artificial selection by man).
The criterion of utility introduces needed objectivity in the determination
of what biological mechanisms are end-directed. Provincial human interests
should be avoided when using teleological explanations, as Nagel says. But he
selects the wrong example when he observes that "the development of corn
seeds into corn plants is sometimes said to be natural, while their
transformation into the flesh of birds or men is asserted to be merely
accidental." 13 The adaptations of corn seeds have developed to serve the
function of corn reproduction, not to become a palatable food for birds or
men. The role of wild corn as food is accidental, and cannot be considered a
biological function of the corn seed in the teleological sense.
Some features of organisms are not useful by themselves. They have
arisen as concomitant or incidental consequences of other features that are
adaptive or useful. In some cases, features which are not adaptive in origin
may become useful at a later time. For example, the sound produced by the
beating of the heart has become adaptive for modern man since it helps the
physician to diagnose the condition of health of the patient. The origin of
such features is not explained teleologically, although their preservation might
be so explained in certain cases.
Features of organisms may be present because they were useful to the
organisms in the past, although they are no longer adaptive. Vestigial organs,

The Autonomy of Biology as a Natural Science


like the vermiform appendix of man, are features of this kind. If they are
neutral to reproductive fitness these features may remain in the population
indefinitely. The origin of such organs and features, although not their
preservation, is accounted for in teleological terms.
To conclude, I will summarize the second part of this paper. Teleological
explanations are appropriate to describe, and account for the existence of,
teleological systems and the directively organized structures, mechanisms and
patterns of behavior which these systems exhibit. Organisms are the only
natural systems exhibiting teleology; in fact they are the only class of systems
possessing internal teleology. Teleological explanations are not appropriate in
the physical sciences, while they are appropriate, and indeed indispensable, in
biology which is the scientific study of org misms. Teleological explanations,
then, are distinctive of biology among all the natural sciences. 14

IE. Nagel, The Structure of Science, New York: Harcourt, Brace and
World, 1961, pp. 338-345.
2E. Nagel, The Structure of Science, p. 338; see also pp. 336-397.
3G. G. Simpson, This View of Life, New York: Harcourt, Brace and
World, 1964, p. 107. According to J. G. Kemeny (A Philosopher Looks at
Science, New York: Van Nostrand, 1959, pp. 215-216) the most likely
solution of the question of the reduction of biology to physics is that a new
theory will be found, covering both fields, in new terms. Inanimate nature will
appear as the simplest extreme case of this theory. In that case, one would
say that physics was reduced to biology and not biology to physics.
4Except for the general conclusion that biological phenomena will never
be satisfactorily explained by mechanistic principles.
sE. S. Russell, The Interpretation of Development and Heredity, Oxford,
1930; see also E. Mayr, "Cause and Effect in Biology," Cause and Effect, D.
Lerner (ed.), New York: Free Press, 1965, pp. 33-50.
6The temperature of the gas is identical by definition with the mean
kinetic energy of the molecules.
7 See Th. Dobzhansky, "Biology, Molecular and Organismic," The Graduate Journal, VII(I), 1965, pp. 11-25.
8For instance, the maintenance of a genetic polymorphism in a
population due to heterosis can be considered a homeostatic mechanism acting
at the population level.
9See F. J. Ayala, "Teleological explanation in evolutionary biology,"
Philosophy of Science, in press.
lOT. A. Goudge, The Ascent of Life, Toronto: University of Toronto
Press, 1961, p. 193.


Biology. History and Natural Philosophy

11 E. Nagel, "Types of causal explanation in science," Cause and Effect,
D. Lerner (ed.), New York: Free Press, 1965, p. 25.
12E. Nagel, The Structure of Science, p. 405; see also F. J. Ayala,
"Teleological explanations in evolutionary biology," Philosophy of Science, in
13 E. Nagel, The Structure of Science, p. 424.
14 It is a pleasure to thank Miss Mary C. Henderson who read the
manuscript and made many valuable suggestions.



The Model of Open Systems:
Beyond Molecular Biology
Ludwig von Bertalanffy
State University of New York at Buffalo

A New View on Scientific Practice and Theory

Two questions appear to have crystallized in our present Colloquium.
First is the question of specialization and generalization. We are all aware that
the enormous content, the complex techniques and sophisticated concepts of
modern science require specialization. On the other hand, the question arises:
Is there nothing common in the sciences-from physics to biology to the
social sciences to history-so that the scientific enterprise must remain a
bundle of isolated specialities, without connecting link and progressively
leading to the type of learned idiot who is perfect in his small field but is
ignorant and unaware of the basic problems we call philosophical, and which
are of primary concern to man in one of the greatest crises of his history?
Secondly-we all feel that this is a time of scientific re-orientation.
Whether this is expressed in the indeterminacy principle of physics and the
gaps in the theory of elementary particles, in biological problems so that
mystical views like those of Teilhard de Chardin are taken into serious
considerations, or in the present dissatisfaction with psychological and
sociological theories-it is the common feeling that something new is required,
and that yesterday's mechanistic universe which has safely guided science
through some 250 years, has come to an end.
One way to approach the problem is what the program of our colloquium
calls "the historical vs. the logical approach." The logical approach, as we find
it in innumerable philosophical writings, is, in broad outline and oversimplification, something like this: We are confronted by observation with sense
data, facts, pointer readings, protocol sentences-whatever expression you
prefer. From these we derive generalizations which, when properly formulated,
are called laws of nature. These are fitted into conceptual schemes called
theories, which in the well-known way of hypothetico-deductive system, allow


Biology. History and Natural Philosophy

for the explanation, prediction and control of nature. The logical operations
involved could be carried through even better and neater with sufficiently
capable computers.
However, personal experience of the scientist as well as the history of
science shows that the actual development of science is nothing of this sort.
Psychology has shown that cognition is an active process, not a passive
mirroring of reality. For this reason, there are no facts as ultimate data;
what we call facts has meaning only within a pre-existing conceptual system.
The famous pointer-readings positivist philosophers were fond to speak of as
being the basis of scientific knowledge simply make no sense without a
conceptual scheme. Whether we read electric currents in a suitable apparatus,
or read oxygen consumption of a tissue in a Warburg machine, or simply read
a watch-the so-called facts of observation make no sense except in a
conceptual construct we already possess and presuppose. In consequence,
history of science does not appear as an approximation to truth, a
progressively improved mirroring of an ultimate reality. Rather, it is a
sequence of conceptual constructs which map, with more or less success,
certain aspects of an unknown reality. For example, one of the first models
was that of myth and magic, seeing nature animated by gods and demons who
may be directed by appropriate practices. Another one was Aristotle's seeing
the universe guided by purposeful agents or entelechies. Then there was the
Newtonian universe of solid atoms and blind natural forces.
Nowadays we seem to be dedicated to still another model, epitomized by
the term "system," of which we shall speak more in detail. Neither were the
previous models and world views simply superstitious nonsense, nor were they
completely eradicated by subsequent ones. The mythical world view served
mankind admirably well through many millenia, and produced unique
achievements, such as the array of domesticated plants and animals which
modern science did not essentially increase. And there is still far too much
demonology around, in science and particularly in the pseudoscience of
politics. Aristotle's physics was a bad model, as was shown by Galileo; but
problems posed by him, such as that of teleology, are still alive in the theory
of evolution-see Teilhard de Chardin-and in the considerations of cybernetics. That our thinking still is much too Newtonian, is the common
complaint of physicists, biologists and psychologists.
The modern reorientation of thought, the new models, appear to be
centered in the concept of system. This would need much more elaboration
than I can provide and I must refer 'to the literature cited. In a very aphoristic
characterization: the procedure of classical science was to resolve observed
phenomena into isolable elements; these, then, can be put together, practically
or conceptually, to represent the observed phenomenon. Experience has
shown that this isolation of parts and causal chains, and their summation and

The Model of Open Systems: Beyond Molecular Biology


superposition works widely, but that now we are presented, in all sciences,
with problems of a more difficult sort. We are confronted with wholes,
organizations, mutual interactions of many elements and processes, systemswhichever expression you choose. They are essentially non-additive, anq
therefore cannot adequately be dealt with by analytical methods. You cannot
split them into isolable elements and causal trains. Compared with the
approach of classical science, they require new concepts, models, methodswhether the problem is that of an atomic nucleus, a living system or a
business organization. Mutual interaction instead of linear causality; organized
complexity instead of summation of undirected and statistical events-these,
somewhat loosely, define the new problems.
One such model is that of the title of my talk-open system. Such
discussion appears to present two advantages. First, we do not talk abstractly
or philosophically about what biology should be, whether it should or
ultimately will be reduced to physics, and so on; rather, we consider concrete
problems of research which, with more or less success, elucidate basic
phenomena of life. Secondly, in so doing, we can shed light on a number of
questions which were asked of the present Colloquium-the question whether
the organism is a machine, whether biology is an autonomous science, the
question of the evolution of biological systems, of Schrodinger's and
Teilhard's ideas, and so forth. When we quite straightforwardly look at the
organism as open system, some philosophical questions take care of themselves!
The Living Machine and its Limitations

An introduction to the open system model can very well start with one
of those trivial questions, which are often very difficult to answer scientifically. What is the difference between a normal living organism, a sick and a
dead organism? From the standpoint of physics and chemistry, we must
answer: None. For from the viewpoint of "ordinary" physics and chemistry, a
living organism is an aggregate of an enormous number of processes which,
sufficient work and knowledge presupposed, can be defined by means of
chemical formulas, equations of physics and the laws of nature in general.
Obviously, these processes are different in a living, sick or dead dog; but the
laws of physics don't tell us a difference; they are not interested whether dogs
are dead or alive. This remains unchanged even if we take into consideration
the last results of molecular biology. One DNA-molecule, protein, enzyme, or
hormone-controlled process is just as good as any other; everyone is
determined by physical and chemical laws, none is better, healthier or more
normal than another.
But there is, no doubt, a fundamental difference between a live and a
dead organism; usually, we don't have any difficulties to distinguish between a


Biology, History and Natural Philosophy

living organism and a dead object. In a living being innumerable chemical and
physical processes are so ordered as to allow the living system to persist, to
grow, to develop, to reproduce, etc. What, however, does this notion of
"order" mean, for which we would look in vain in textbooks of physics and
chemistry? In order to be able to define and explain it we need a model, a
conceptual construct. One such model was used since the beginnings of
natural science. This was the model of the living machine. Depending on the
state of the art, the model found different interpretations. When in the 17th
century Descartes introduced the concept of the animal as a machine, only
mechanical machines existed. Hence the animal was a sort of complicated
clockwork. Thus Borelli, Harvey and other so-called iatrophysicists explained
the function of muscles, of the heart, etc., by mechanical principles of levers,
of a pump and the like. You can still see this in a musical opera, when in the
Tales of Hoffmann the beautiful Olympia turns out to be an artful doll, a
clockwork or automaton as it was then called. Later on the steam engine and
thermodynamics were introduced, which led to the organism being conceived
as a heat engine, a fact to which we owe the calculation of calories, for
example. As it turned out, however, the organism is not a heat engine,
transforming the energy of fuel first into heat and then into mechanical
energy. It rather is a chemica-dynamic machine, directly transforming the
chemical energy of fuel into effective work, a fact on which, for example, the
theory of muscle-contraction is based. Lately, self· regulating machines came to
the fore, such as the thermostat, missiles aiming at a target and the
servomechanisms of modern technology. In parallel, the organism became a
cybernetic machine. The most recent development are molecular machines.
When we talk about the "mill" of the Krebs cycle of oxidation or about the
mitochondria as the "power-plant" of the cell, this means that machine-like
structures on the molecular level determine the order of enzyme reactions;
similarly, it is a micromachine which transforms or translates the genetic code
of the DNA of the chromosomes into proteins and eventually into a complex
Nevertheless, the machine model of the organism has its difficulties. One
is the problem of the origin of the machine. Old Descartes didn't have a
problem because he explained the "animal machine" as the creation of a
'divine watchmaker. But how do machines come about in a universe of
undirected physico-chemical events? Clocks, steam engines and transistors
don't grow by themselves in nature. Where do the infmitely more complicated
living machines come from?
Secondly, there is the problem of regulation. Self·repairing machines are
conceivable in terms of modern automata theory. However, the problem arises
when regulation and repair take place after arbitrary disturbances. Can a
machine such as an embryo or a brain be programmed for regulation, not

The Model of Open Systems: Beyond Molecular Biology


after a defined disturbance or a finite set of disturbances, but an indefinite
number of disturbances? Here, it seems, is a limit for the logical automaton or
the so-called Turing machine, which arises from "enormous" numbers. The
Turing machine can, in principle, resolve even most complex operations into a
finite number of steps. But the number may be neither finite and countable
nor infinite and non-countable, but just "enormous," that is, of a higher order
than, for example, the number of elementary particles in the universe. Such
enormous numbers do appear, e.g., in the interactions of even a moderate
number of elements, for example, genes or nerve cells.
Even more important is a third question. The living organism is
maintained in a continuous exchange of its components; metabolism is the
basic characteristic of living systems. It is, as it were, a machine composed of
fuel, spending itself continually and yet maintaining itself. Such machines do
not exist in present technology. In other words: A machine-like structure of
the organism cannot be the ultimate reason of order of life processes, because
the machine itself is maintained in an ordered flow of processes. The primary
order must, therefore, lie in the process itself.
The Model of Open System: A Scientific Approach to Organismic Biology

We express this by saying that living systems are essentially open systems.
An open system is defined by the fact that it exchanges matter with its
environment, that it persists in import and export, building-up and breakingdown of its material components. But here we are immediately confronted
with difficulties. When 30 years ago I proposed the model of the organism as
open system, there was no theory of such systems. Rather, kinetics and
thermodynamics, the fields of physics concerned, were by definition restricted
to closed systems, that is, systems without exchange of matter. The theory of
open systems is therefore a relatively recent development and leaves many
problems unsolved. The development of a kinetic theory of open systems has
two roots: first the biophysical problem of the organism; second, developments in industrial chemistry which increasingly applies continuous i.e. open
reaction systems which have greater efficiency and other advantages compared
to reactions in a closed system. The thermodynamic theory of open systems is
called irreversible thermodynamics. It has become an important generalization
of physical theory through the work of Meixner, Onsager, Prigogine and
As in any physical theory, we must start with simple models. Already
simple open systems (Fig. I a) show remarkable characteristics, apparent from
the solution of the set of simultaneous equations which define them. Under
certain conditions, open systems approach a time-independent state, a steady
state or Fliessgleichgewicht. The steady state is maintained in distance from
true equilibrium and is therefore capable of doing work-as is the case in


Biology, History and Natural Philosophy

living systems, in contrast to systems in equilibrium. Furthermore, the system
remains constant in its composition, in spite of continuous irreversible
processes taking place, i.e. import and export, building-up and breaking-down
of components. If such steady state is reached in an open system, it is
independent of the initial conditions, and determined only by the system
parameters, that is, the rates of reaction and transport. We call this
equifinality, and it is found in many organismic processes, for example in
growth: The same final state or "goal," that is, the same speciescharacteristic, the final size may be reached from different initial sizes and
after arbitrary disturbances of the growth process (Fig. 2).

_ _K--,-I_.~ A _ _














Figure 1 a. Model of a simple open system, showing maintenance of constant
concentrations in the steady state, equifinality, adaptation and stimulus-response, etc. The
model can be interpreted as a simplified schema for protein synthesis (A: amino acids, B:
protein, C: deamination products; k J : polymerization of amino acids into protein, k 2 :
depolymerization, k3: deamination; k2« kl' energy supply for protein synthesis not
indicated). In somewhat modified form, the model is Sprinson and Rittenberg'S (1949)
for calculation of protein turnover from isotope experiments. (After von Bertalanffy
1953.) lb. The open system of reaction cycles of photosynthesis in algae. (After Bradley
and Calvin 1957.)


The Model of Open Systems: Beyond Molecular Biology














f--'" 1' .... -


/ ' r--

'-" ' ........

.... /






f..- ....







100 125 150 175
Time in days


225 250



Figure 2. Equifinality of growth. Heavy curve: normal growth of rats. Broken curve: at
the 50th day, growth was stopped by vitamin deficiency. After re-establishment of
normal regime, the animals reached the normal final wetght. (After Hober from von
Bertalanffy 1960.)

From the viewpoint of thermodynamics, open systems can maintain
themselves in a state of high statistical improbability, of order and
organization. The reason is in the expanded entropy function of Prigogine. In
closed systems, entropy and therefore disorder must increase owing to
irreversible processes. In open systems, there is not only entropy production
due to irreversible processes but also entropy transport due to import of
matter as potential carrier of free energy or negative entropy. This is the basis
of the negentropic trend in organismic systems and for Schrodinger's
statement that the organism feeds on negative entropy. For this reason, open
systems may even advance toward increasing differentiation and organization
as is the case in the biological phenomena of development and evolution. In
this way, an apparent contradiction between the inorganic and living universe
is resolved. According to the second principle of thermodynamics, the general
direction of physical events is toward increasing entropy, that is, toward states
of increasing probability and decreasing differentiation. Organisms can evolve
toward decreasing probability and increasing differentiation, because they
represent open systems, exchanging matter with their environment.
The simple model I have shown is, so to speak, the granddaddy of more
elaborate ones. One can, of course, mathematically set up much more
complex models to study their properties, and find complex open systems
both in nature and in industrial processes. I mention only two developments
because of their theoretical implications: computerization and compartment
theory. The solution of sets of simultaneous equations becomes most tiring


Biology, History and Natural Philosophy

with a larger number of reactants and equations; and if the equations are
nonlinear, there is no general way to solving them.
Here the computer comes in, which can yield solutions for such problems.
This is more than technique and facilitation of calculation; for nonlinearity is
an obstacle in principle in solving more complex systems, and so the computer
opens quite a new field. To give just one example, Benno Hess has analyzed
the 14-step reaction chain of glycolysis in the living cell by way of a
mathematical model of more than 100 nonlinear differential equations.
Comparable analyses are routine in eco~omics, market analysis, etc. This
further makes possible simulation. Instead of investigating in the laboratory
the complex interactions in a network of processes, one can do so easier on
the computer, working out a suitable model and testing it against experiment.
Compartment theory is concerned with the fact that reactions may take place,
not in a homogenous space but in sub-systems which are partly permeable to
the reactants. This obviously applies to many processes in the cell, and there
are highly elaborate mathematical techniques to deal with such cases.
Compared to conventional closed systems, open systems show characteristics which seem to contradict the usual physical laws and were often
considered as vitalistic characteristics of life, that is, as violations of physical
laws explainable only by introducing soul-like or entelechial factors into the
organic happenings. This is true of the equifinality of organic regulations, if
for example the same "goal," i.e. a normal organism, is produced by a normal
zygote, the half of a zygote, two zygotes fused, etc. This in fact was the most
important, so-called proof of vitalism of Driesch. A similar consideration
applies to the apparent contradiction between the tendency towards increasing
entropy and disorder in inanimate nature, and negentropic processes in organic
development and evolution. The apparent contradictions disappear with the
expansion and generalization of physical theory to open systems.
In a discussion addressed to biologists, I would now have to show that
the model of open system works, i.e. that it has power to explain phenomena
previously not accounted for. We are here concerned with general and
philosophical questions, so I must forego such discussion, and limit myself to
quoting a few examples in the way of illustration.
There is, first, the wide field that has substantiated Goethe's Stirb und
Werde, the continuous decay and regeneration, the dynamic structure of living
systems at all levels of organization. Broadly we may say that this
regeneration is taking place at far higher turnover rates than had been
anticipated, Table 1. For example, it is certainly surprising that a calculation
on the basis of a steady-state model revealed that the proteins of the human
body have a turnover time of not much more than a hundred days. Essentially
the same is true for cells and tissues. Many tissues of the adult organism are
maintained in a steady state, cells being continuously lost by desquamation


The Model of Open Systems: Beyond Molecular Biology

Turnover rates of intermediates of cellular metabolism (After Hess 1963)
ATP glycolysis
ATP glycolysis + respiration
ATP glycolysis + respiration
citrate cycle intermediates
glycolytic intermediates
Fe 2 +/Fe 3 + - cytochrome a
Fe 2 +/Fe 3 + - cytochrome a3



turnover time
in seconds

total organism
total organism
ascites tumor
ascites tumor
ascites tumor
wing muscle
ascites tumor

1.3 X 10 6
1.5 X 10 7
1.7 X 10 6
1.2 X 10 6
9.5 X lOS
4.8 X 104
4.4 X 10 3
2.2 X 10 3
1.6 X 10 3
4.8 X 10 2
4.0 X 10 1
1 - 10
0.1 - 8.5
4.6 X 10-2
1.9 X 10- 3

and replaced by mitosis. Prior to such investigations, it was hardly expected
that cells in the digestive tract or respiratory system have a life span of only a
few days, Table 2.
After having extensively explored the paths of individual metabolic
reactions in biochemistry, it has now become a pressing task to understand
integrated metabolic systems as functional units. This is being done in the
complex network and interplay of scores of reactions in functions such as
photosynthesis (Fig. 1 b), respiration and glycolysis. Here an important
insight is implied. We begin to understand that beside visible morphologic
organization, as we observe it macroscopically, with the ordinary or
electron-microscope, there exists another, invisible organization, resulting from
interplay of processes and defending itself against disturbances. With more
time, I could show how the theory of open systems is applicable to many
biological phenomena, such as phenomena of adaptation, action potentials,
transport processes, pharmacodynamic action, growth, excitation, the energetics of the organism and many others.
Behind these facts we rriay trace the outline of an even further
generalization. The theory of open systems is part of general system theory.
This is a doctrine concerned with principles that apply to systems in general,
irrespective of the nature of their components and the forces governing them.
With general system theory we reach a level where we no longer talk about
physical and chemical entities, but discuss wholes of a completely general


Biology, History and Natural Philosophy

Rate of mitosis in rat tissues (after F. D. Bertalanffy 1960)
daily rate
of mitosis
(per cent)
Organs without mitosis
nerve cells, neuroephithelium, neurilemma, retina, adrenal medulla ......................


Organs with occasional mitosis but no cell
liver parenchyma, renal cortex and medulla,
most glandular tissue, urethra, epididymis, vas
deferens, muscle, vascular endothelium, cartilage, bone ............................. .

less than 1

Organs with cell renewal
upper digestive tract .................... .
large intestine and anus .................. .
stomach and pylorus .................... .
small intestine ......................... .
trachea and bronchus .................... .
ureter and bladder ...................... .
epidermis ............................. .
sebaceous glands ....................... .
cornea ............................... .
lymph node ........................... .
pulmonary alveolar cells ................. .
seminiferous epithelium ................. .

7 - 24
10 - 23
11 - 54
64 -79
1.6 - 3


4.3 - 10
1.9- 9.1
1.3- 1.6
26.7 - 47.6
33 - 62.5
19.1 - 34.5

nature. Yet, certain principles of open systems still hold true and may
successfully be applied at large, from ecology, the competition and equilibrium among species, to economics and other fields of sociology.
Unsolved Problems

At present, we do not have a thermodynamic criterion that would
characterize the steady state in open systems in a similar way as maximum
entropy defines equilibrium in closed systems. It was believed for some time
that such criterion was provided by minimum entropy production, a statement
known as "Prigogine's Theorem." However, Prigogine's Theorem, as was well
known to its author, applies only under restrictive conditions. In particular, it
does not define the steady state of chemical reaction systems.
Another unsolved problem of a fundamental nature originates in a basic
paradox of thermodynamics. Eddington called entropy "the arrow of time."
As a matter of fact, it is the irreversibility of physical events, expressed by the
entropy function, which gives time its direction. Without entropy, that is, in a

The Model of Open Systems: Beyond Molecular Biology


universe of completely reversible processes, there would be no difference
between past and future. However, the entropy functions do not contain time
explicitly. This is true of both the classical entropy function for closed
systems by Clausius, and of the generalized function for open systems and
irreversible thermodynamics by Prigogine.
Here we come into territory which is still largely unexplored. We can
hardly doubt that in the living world there is a general phenomenon which
can be termed anamorphosis, that is, increase in order and organization which
is found in the development of an individual as well as in evolution. We have
heard that this is not a violation of the second law of thermodynamics as was
often assumed. But what, actually, determines the process? Thermodynamics
presents no answer. We could further think of evolution as an accumulation of
genetic information, i.e. the genetic code represented by the DNA of the
chromosomes. But why does information accumulate in this special case of
the genetic code, while in general, information is not only not preserved but is
progressively dissipated into noise? The conventional answer given is the
theory of selection. The so-called synthetic theory considers evolution as the
result of chance mutations, that is, in a well-known simile, of "typing errors"
which occasionally occur in the reduplication of the genetic code; the process
being directed by selection, i.e. the survival of populations or genotypes with
highest differential reproduction, that is, which produce the highest number of
offspring under existing external conditions. Similarly, the origin of life is
explained by a chance appearance of organic compounds (amino acids,
nucleic acids, enzymes, ATP, etc.) in the primeval ocean which, by the way
of selection, eventually formed reproducing units, virus-like forms, protoorganisms, cells, etc.
In contrast to this conventional view, it should be pointed out that
selection, competition and "survival of the fittest" already presuppose the
existence of self-preserving (and hence competing) systems; this can therefore
not be the result of selection. At present we do not know of any physical law
according to which, from a "soup" of organic compounds, self-preserving open
systems are formed and maintained in a state of highest improbability.
Likewise, even if such systems are accepted as "given," there is no physical
law stating that evolution on the whole proceeds in the direction of increasing
organization, i.e. improbability ("anamorphosis"). Selection of genotypes with
maximum offspring doesn't help much in this respect; it is hard to understand
why evolution ever should have gone beyond rabbits, herring or even bacteria
which are unrivaled in their reproduction rate. Production of local conditions
of higher order (and improbability) is physically only possible if "organizational forces" of some kind enter the scene; this is the case in the formation
of crystals, where "organizational forces" are represented by valences, lattice
forces and the like. Such organizational forces, however, are explicitly denied
when the genome is considered as an accumulation of "typing errors."


Biology, History and Natural Philosophy

Apparently, we need something more beyond conventional synthetic
theory of evolution. One aspect is "organizational" forces and laws. As a
matter of fact, we see with the electron-microscope structures far surpassing
those encountered in ordinary physics and chemistry; insight into the laws of
at least simpler supramolecular structures is slowly proceeding. "Biotonic"
laws, as Elsasser calls them, at all levels of organization are apparently present,
but are as yet known only in their visible manifestation.
The Russian biophysicist Trincher (1965) came to the conclusion that the
entropy function is not applicable to living systems; he contrasts the entropy
principle of physics with biological "principles of adaptation and evolution"
expressing an increase of information. Here we have to consider, however, that
the entropy principle has a physical basis in the Boltzmann derivation, in
statistical mechanics and the transition to more probable distributions as it
takes place in processes at random; while presently no physical explanation
can be given for Trincher's phenomenological principles.
We can also speak of "internal" factors in evolution contrasted with
"external," the outer-directedness of evolution expressed in the theory of
selection. Following an ingeneous analysis by Herbert Simon, evolution
appears to be connected with hierarchical order: Only by putting together
subhierarchies, not by assembling complex systems from the start, it appears
to be possible to have evolution in an acceptable time scale. However, what
Simon calls stable hierarchic intermediates amounts to the same as what I
called organizational principles-that is, supramolecular forces and laws that
hold electron-microscopic, cell and super cellular structures together; and for
this, Simon does not provide an explanation. These (and other) formulations
mean essentially the same, and are different names for the same phenomenon
and problem. We must admit that at present we do not have a theory.
Presumably, irreversible thermodynamics, information theory, dynamical system theory, theory of structures higher than molecular ones, theory of
hierarchic order and possibly others, will have to be united in a new way to
account for anamorphosis. We have various hints in such direction, but
nothing resembling a consistent theory.
The concept of the organismic model as an open system has proved to be
very useful in the explanation and mathematical formulation of numerous life
phenomena; it leads, as is to be expected in a scientific working hypothesis, to
further problems, which are partly of a fundamental nature. This implies that
it is not only of purely scientific but also of "meta-scientific" significance.
The mechanistic concept of nature predominant so far emphasized the
dissolution of happenings into linear causal chains, a conception of the world
as a result of chance events or a physical and Darwinian "play of dice" (to
quote Einstein's well-known saying) and the reduction of biological processes
to laws presently known from inanimate nature. In contrast to this, in the

The Model of Open Systems: Beyond Molecular Biology


theory of open systems (and its further generalization in general system
theory) principles of multivariable interaction (e.g. reaction kinetics, flows
and forces in irreversible thermodynamics, Onsager reciprocal relations)
become apparent, a dynamic organization of processes and a possible
expansion of physical laws under consideration of the biological realm. These
developments therefore form part of a new formulation of the scientific world

The following is a small selection of works quoted in the text or
suggested for further reading on topics discussed.
Beier, W. Biophysik, 3rd edition. Jena: Fischer, 1968. English translation in
Bertalanffy, F. D., and C. Lau, "Cell Renewal," Int. Rev. eyto!. 13 (1962),
von Bertalanffy, L., Biophysik des Fliessgleichgewichts. Translated by W. H.
Westphal. Braunschweig: Vieweg, 1953. Revised edition with W. Beier
and R. Laue in preparation.
von Bertalanffy, L., "Chance or Law," in Beyond Reductionism, edited by A.
Koestler and J. R. Smythies. London: Hutchinson, 1969.
von Bertalanffy, L., Robots, Men and Minds. New York: Braziller, 1967.
von Bertalanffy, L., General System Theory. Foundations, Development,
Application. New York: Braziller, 1968.
von Bertalanffy, L., "The History and Status of General System Theory," in
Trends in General Systems Theory, edited by G. Klir. New York: Wiley,
in press.
Denbigh, K. G., "Entropy Creation in Open Reaction Systems." Trans.
Faraday Soc. 48 (! 952), 389-394.
General Systems, L. von Bertalanffy and A. Rapport (eds.), Society for
General Systems Research, Joseph Henry Building, Room 818, 2100
Pennsylvania Avenue, N.W., Washington, D.C. 20006, 12 vols. since 1956.
Hess, B., "Fliessgleichgewichte der Zellen," Dt. Med. Wschr., 88 (! 963),
Hess, B., "Modelle enzymatischer Prozesse." Nova Acta Leopoldina (Halle,
Germany), 1969.
Rescigno, A., and G. Segre, Drug and Tracer Kinetics, Waltham (Mass.):
Blaisdell, 1966.
Rosen, R., Dynamical System Theory in Biology. Vol. I, Stability Theory and
its Applications. New York: Wiley, 1970.
Simon, H. A., "The Architecture of Complexity," General Systems 10 (! 965),


Biology, History and Natural Philosophy

Trincher, K. S., Biology and Information: Elements of Biological
Thermodynamics. New York: Consultants Bureau, 1965.
Unity Through Diversity, edited by W. Gray and N. Rizzo, Vol. II: General
and Open Systems. New York: London: Gordon and Breach, 1971.
Weiss, P. A., Life, Order and Understanding. The Graduate Journal, Vol. III,
Supplement, University of Texas, 1970.
Whyte, L. L., Internal Factors in Evolution. New York: Braziller, 1965.
Whyte, L. L., A. G. Wilson and D. Wilson (eds.), Hierarchical Structures. New
York: Elsevier, 1969.
Yourgrau, Wolfgang, A. Van der Merwe and G. Raw, Treatise on Irreversible
and Statistical Thermophysics. New York: Macmillan, 1966.



Eleetronie Mobility in
Biologieal Proeesses
Albert Szent-Gyorgyi
Institute for Muscle Research at the Marine Biological Laboratory
Woods Hole, Massachusetts

If you would ask a chemist to fipd out for you what an electric dynamo
is and does, the first thing he would do is to dissolve it in hydrochloric acid.
A molecular biologist would fare, perhaps, better. He might take the dynamo
to pieces and describe the single pieces with the greatest care. However, if you
would suggest to him that maybe there is an invisible fluid, electricity, flowing
in that machine, and once he has taken it to pieces that fluid could not flow
anymore, then he would scold you as a vitalist which is worse than to be
called a communist by an FBI agent.
As you all know, biology at the moment stands entirely under the
influence of the molecular concepts. Molecular biology tells us that the living
organism is built up of very small closed units, molecules, and, consequently,
what we have to know is the nature and composition and structure of these
molecules and if we know all about them we will know all about life; the rest
of it will take care of itself. What I want to do with you is to scrutinize this
concept, that is, discuss with you the conceptual foundations of present
biology, whether life processes can be fully explained and accounted for by
molecules. I would add to all this that these molecules are macromolecules,
that is, very big molecules which are very clumsy, very immobile. What gives
special charm to biological research is the great subtlety of biological reactions
and I have always found it difficult to believe that such a very subtle
instrument as a living cell could be fully explained by the mutual relation of
these clumsy, immobile units. I always felt that there must be something more
in biology, something which engenders this great mobility and subtlety of the
reactions. As you all know, the molecules are built up of atomic nuclei and
electrons. The nuclei, practically, play no part in biology, they only act as
charged points around which the electrons are arranged. All the biological
phenomena thus must be due, in one way or another, to the reactions of


Biology, History and Natural Philosophy

these electrons. These electrons are very small, and very mobile, and I always
have the feeling that the subtle biological reactions are due to the motion of
electrons. Thus, for many years, I advocated an extension of biochemical
research into the electronic dimension, and I even have written two little
monographs about this subject, one under the title Bioenergetics and the other
under the title Introduction to a Submolecular Biology. (Both are published
by the Academic Press in New York.) It is now more than eight years ago
that the second monograph has appeared and since then I have given very
much time and thought to the study of electronic reactions.
The first and most basic question is now whether these electrons can have
a more or less independent existence and mobility. Whether they can go from
one molecule to the other producing those subtle reactions, or if they are
chained to their units, the whole molecules which can participate in reactions
only as one single whole closed unit.
Your program quotes a Chinese saying, according to which the longest
journey of ten thousand leagues also begins with the first step. Therefore, if
electrons do possess a mobility in biological systems the first question would
be: how can they move within a molecule or go from one molecule to the
other? Is there any possibility for such an electronic mobility?
I can give you the answer right away-it is affirmative.
Louis Brillouin has shown that if a molecule consists of regular repeat
units, then the electrons within these single units disturb one another and
their energy levels split up. If these electrons are not separated by very wide
barriers, these levels conflow. And if such a big molecule has many units
which contribute to the system there are many electron levels. Since each
electron level splits up in two, there will be twice as many electronic levels as
there are units, and in macromolecules this number can be very high. These
many electron levels can more or less conflow to a continuous energy band,
which can extend over the whole molecules. Whether the electrons will have
free mobility in such an electron band depends on their number. According to
the Pauli exclusion principle, no more than two electrons can be on the same
energy level and this only if the two electrons have an opposite spin. So the
maximum number of electrons which can be placed in such a band is the
double of the number of the repeat units of that molecule which contributed
to the band. If the number of the units is N and the number of the electrons
in the band is 2N, then the band is saturated. This means there is no room for
an extra electron and no room for mobility. The situation is similar to a very
crowded cocktail party in which you can't move. To be able to move you
have to wait till somebody leaves the room. So if, in this energy band, we
should give a push to one electron in one direction, another electron will have
to go the same length of the way in the opposite direction and there will be
no net displacement and no electric conductivity.

Electronic Mobility in Biological Processes


In biology we are concerned, primarily, with protein molecules and so our
first question is: do protein molecules have energy bands? There has been a
great deal of discussion about this problem and as things stand today we have
reason to believe that there are conduction bands in proteins. The question,
only, is whether they are conductant-and this will depend on the number of
electrons. It seems that in a protein molecule the number of electrons in such
a band is 2N, that is, if there is such a band it is saturated, so in itself it
could not conduct electricity and could not be the foundation of an
electronic mobility. However, there are two possibilities of making such a
system conductant. The single energy bands are separated from one another
by "forbidden zones" in which no electron is allowed. Hence, the highest
filled energy band has on top of it an empty band. Now the question is: how
wide is this forbidden zone? If this forbidden zone is very narrow then even
heat agitation could kick up an electron from the highest filled energy band
to the lowest empty band. The question is thus: how wide is the forbidden
zone in proteins? The calculations show that it is in the order of