Chapter 2. Panpsychism and Science by Sewall Wright

Mind in Nature: the Interface of Science and Philosophy
by John B. and David R. Griffin Cobb, Jr.

Chapter 2. Panpsychism and Science by Sewall Wright

Sewall Wright has been Ernest D. Burton Distinguished Service Professor at the University of Chicago and Leon J. Cole Professor of Genetics at the University of Wisconsin. He has been Professor Emeritus at Wisconsin since 1960.

I am speaking here as a zoologist, specifically a geneticist, who has been concerned with the implications of his field for the philosophy of science. While it is a field that is much less mature than physics, it occupies such a central position in the general field of knowledge that its implications should be given special weight.

A physicist or chemist can get along fairly well with a commonsense dualism in attempting to discover the laws of nature which govern the vast world of inanimate things. The occurrence of beings like himself, composed of matter that seems to be inhabited by minds capable of some control over the course of events, may be somewhat disturbing, but mankind constitutes such an infinitesimal portion of the cosmos that the physical scientist may for the moment ignore it in his difficult task of finding the basis of cosmic order.

The humanists and social scientists can adopt the same commonsense philosophy while concerning themselves solely with the activities of human beings.

The biologist is continually in trouble. The objects of his study range from a class of molecules that have the basic self-duplicating property of living things, through cells which suggest purely physical systems, through animals which give increasing evidence of having minds, to human beings in whom streams of consciousness seem to involve continual choices of action, at the opposite pole from control by impersonal laws of nature. The zoologist cannot escape the problem of the relation of matter and mind.

Implications of Physical Science

Let us compare further the two kinds of knowledge which must somehow be reconciled in a unified philosophy of science. While the physical scientists have not yet arrived at a fully satisfactory account of the most elementary particles, they have acquired precise knowledge of the hierarchy of entities starting from proton, neutron and electron, through atom and molecule, to objects of our own order of size for which the precision of the laws of mechanics have made possible the extraordinary achievements of technology. Beyond this comes the detailed knowledge of the surface of the earth of the geologist, the astronomer’s knowledge of the sun and planets, stars in general, our galaxy and the array of galaxies, leading again to the fringes of knowledge in cosmological studies.

The dominant philosophy of physical science since the time of Galileo, with some wavering in the present century, has been that of the famous dictum of Laplace:

An intellect which at a given instant knew all the forces acting in nature and the positions of all things of which this world consists -- supposing the said intellect were vast enough to subject these data to analysis -- would embrace in the same formula the motions of the greatest bodies in the universe and those of the slightest atoms; nothing would be uncertain for it, and the future, like the past, would be present to its eyes.

Streams of Consciousness

In marked contrast is the kind of knowledge provided to each person in his own stream of consciousness. At any moment this has a focus, but one which shifts continually, now on perception of the outside world, now on a memory which has somehow been stored out of mind (perhaps for many decades), now on an emotional state, now on a toothache, now on construction of an abstract pattern of thought, now on communication with others, but again and again on the often painful process of choosing among courses of action, and then of acting.

Nothing could contrast more than the precise determinism of our knowledge of the external world when pains are taken to control conditions, and the fitful character and apparent freedom of choice of the stream of consciousness.

The latter, nevertheless, is obviously the primary reality. The former is wholly derived from bits of the streams of consciousness of many observers and is restricted to those aspects which can be communicated. It can be stored best in books, but actively exists only in minds, within which it appears to consist of a set of rather pale second-hand deductions. Its restriction to the so-called primary properties of matter (location in space, changes in this, and association of matter with forces describable in turn only by changes in location) contrasts with the richness of the stream of consciousness. Colors and sounds are reduced to wavelengths; sensations of heat and cold are reduced to readings on a thermometer; taste, smell, feel are ignored in precise formulations.

It now turns out, moreover, that even position in space is not absolute but relative to circumstances of the observers, each of whom has his own private four dimensions of space and time for locating events. Apparently exact agreement is possible only because communication is restricted to observers who are not moving relatively to each other at velocities of more than a minute fraction of the velocity of light.

Moreover, all of this common knowledge of the so-called primary properties is based on measurements in terms of units: centimeter, gram, second, with operational definitions which are recipes for voluntary actions. Reality clearly consists primarily of streams of consciousness. This fact must take precedence over the laws of nature of physical science in arriving at a unified philosophy of science, even though it must be largely ignored in science itself.

Statistical Laws of Nature

In my own case, I started as a student with the usual conviction that biology, and science in general, requires a rigorously deterministic viewpoint. I still, indeed, hold this viewpoint in practice, but with a radical revision of the philosophical implications of science. My deterministic viewpoint in zoology was somewhat disturbed by reading Bergson in 1912, but not for long. What really made over my thinking was reading (in 1914) Karl Pearson’s Grammar of Science (published in 1892), and a book, The Origin and Nature of Life (1912), by the biochemist, Benjamin Moore. Curiously enough the philosophic position that I arrived at was not held by either and was vigorously opposed by Pearson.

What I derived from Pearson was a different attitude toward what I then considered the absolute laws of nature. He treated them as merely condensed descriptions of how things are observed to behave, no different in kind from statistical laws describing human behavior, such as the law of supply and demand or the regression of marriage rate on the volume of trade.

Another idea that he firmly implanted was the uniqueness in principle of every event:

The causes of any individual thing thus widen out into unmanageable history of the Universe. . . It is useful to remember how essentially the causes of any finite portion of the Universe to the history of the Universe as a whole.

Thus it is not possible to deal deterministically with single events. Science can only deal with classes of more or less similar events and thus is necessarily statistical.

The Physical and Biologic Hierarchies

From Moore, I derived a vivid appreciation of the importance of the hierarchic structure of existence. The crucial point was that a living organism is more comparable to a molecule or atom among inanimate things than to a mere unorganized aggregation of materials like a stone. Conversely a molecule or atom might seem much like a little organism if we could observe the incessant activity which the physical scientists now attribute to them.

These ideas and others seemed to me to point to dual-aspect panpsychism as the simplest synthesis, in spite of the opposition of Pearson to any metaphysical speculation and Moore’s ignoring of the issue.

I must admit that I have not found many scientists who appreciate its simplicity. The only member of the faculty of the University of Chicago with whom I discussed it during my long stay there who at all shared this viewpoint was Charles Hartshorne of the Philosophy Department, who had arrived at it along an utterly different route. Among zoologists, much the closest in viewpoint seems to be Bernard Rensch, who probably also arrived at it along a different route.

Matter and Mind

There have been several different views of the relations between matter and mind. It is impossible, as brought out by Berkeley and Hume, to disprove solipsism, the view that the observer’s stream of consciousness is all that exists. Most babies, however, probably learn within a week or two after birth that they are subject to combinations of unwished-for sensations of such consistency as to indicate something real. With the later dawn of self-consciousness, they learn that there are others with streams of consciousness like their own who can be communicated with. I should emphasize here, to avoid what seems to be a common misunderstanding, that the term ‘consciousness’ by no means necessarily implies self-consciousness.

Primitive peoples are said to share the animistic viewpoint that all things are more or less like human beings in their capacities for spontaneous action. At a later cultural stage a sharp distinction is usually made between two kinds of existence which, it is supposed, may occur separately as mindless matter and as disembodied mind but, at least in man, in an association of body and soul. It is usually thought that this is indissoluble in life but that the soul persists after death without communication with the living. The spiritualists, including some scientists, however, believe that communication with disembodied spirits is a real phenomenon. The regularity with which supposed evidence has been shown to be fraudulent, as well as the difficulty of reconciliation with natural science, has led most persons to profound skepticism.

Modern science has developed in the main under the concept that nonliving matter is wholly mindless and is subject to completely deterministic laws of nature. A good many scientists have held, however, that there is some vital principle in all living things, not necessarily mind, which is absent in nonliving matter. The list of leading recent biologists who have been vitalists includes Hans Driesch, S.H. Jannings, Ralph Lillie and Edmond Sinnott. Bergson developed his philosophical system around the concept of an elan vital.

Most scientists as well as most nonscientists have probably assumed that the higher animals, at least, have minds; though some, no doubt, have followed Descartes in considering all living beings other than man as mere automata.

The prevailing trend in biology, however, has been away from vitalism and any causal influence of mind on the course of events, toward a complete reduction to the principles of physics and chemistry. Jacques Loeb was the leader in America at the beginning of this century in insisting on the exclusion of all but physico-chemical explanations in biology. The limit of this trend would seem to be complete materialism, the denial of mind as a category of existence. This, however, is an absurdity. Mind, even though denied any role in the inexorable course of events, must be retained at least as an observer.

Emergence of Life and Mind

If the nonliving world is completely devoid of mind and if, as it seems necessary to believe, there was a time when no life could have existed, living beings must either have had a supernatural origin or have been developed somehow from nonliving matter. Linnacus accounted for the origin of all species of plants and animals by separate creation. Lamarck, by advocating evolution, pushed creation back to a possible single origin of life.

The apparent gap between nonliving and living has now been bridged by nucleic acids, a class of polymeric organic molecules composed of a succession of small units (nucleotides) of four sorts, the order of which determines an indefinitely large number of different specificities. The latter is also true of the proteins (composed of 20 kinds of amino acids). They are the principal component, other than water, of all living forms, but the nucleic acids alone have the remarkable property of being capable of duplicating their patterns, whatever they may be, from small molecules in their medium. They may be considered living molecules. They can evolve by duplication of their specificities as of the new type if, by any accident, they undergo a change (or mutation). They, as genes, are the units of heredity. They determine the synthesis of protein molecules of the most diverse specificities according to a code in which succession of three nucleotides determine one amino acid. The essential identity of the code in the most diverse organisms is strong evidence for a single origin of life on earth.

Nucleotides and amino acids are substances which, there is reason to believe, could have been formed, and polymerized into nucleic acid and protein respectively, under certain conditions on a lifeless earth. The origin of living organisms from lifeless matter is thus a reasonable hypothesis.

This brings us back to the question of the origin of the mind. Lloyd Morgan (1933; cf. Wright 1935) treated the origin of mind in the course of evolution as a phenomenon of the same sort as the emergence of a new organ or physiological capacity. A new organ, however, involves nothing more mysterious than differential growth, leading for example to an outpocketing from flat tissue that turns out to be useful and can be further elaborated. Similarly, loss, addition or rearrangement in a protein molecule may enable it to bind other molecules in such a way as to catalyze a new metabolic process. Emergence of either of these sorts, however surprising their consequences, poses no serious philosophical difficulty. Emergence of mind from no mind at all is sheer magic. We conclude that the evolution of mind must have been coextensive with the evolution of the body. Moreover, mind must already have been there when life arose and indeed must be a universal aspect of existence -- still assuming that mind cannot arise from nothing.

The emergence of mind in the course of individual development from the fertilized egg presents a similar problem and one that is an everyday occurrence instead of a single event in the remote past. It would appear that the mind of a human being must develop from something of the nature of mind in the fertilized egg and, back of this, in the separate germ cells and in the nucleic acid molecules.


As already noted the living cell, because of its tightly organized character, is more comparable to a molecule than to a mere aggregation of matter. It may be thought of as a supermolecule composed principally of C, H, O, N, P and S. Multicellular organisms, including man, are in turn not mere aggregations of cells, but so tightly organized that they may be considered super-super-molecules, ultimately with properties which are wholly those of the component atoms in the very complex combination. The arguments from continuity require the presence of mind in cells and, back of this, in molecules, atoms, and all that exists.

This can be looked at in two ways: According to dualistic panpsychism, matter and mind are two modes of existence which are universally associated. In the philosophy of Spinoza such an association was a necessary consequence of his identification of God and the universe and his conception of extension and thought as two of the attributes of God.

This dualistic panpsychism is not quite the same as monistic panpsychism, according to which mind and matter are merely two aspects of the same reality: as it is to itself and as it seems to other minds with which it interacts.


If A and B represent two minds, largely private, but nevertheless capable of interacting directly or indirectly: A perceives certain regularities in its stream of consciousness which it ascribes to an external reality, B; but, as it does not enter into B’s stream of consciousness, it in general tends to consider B as merely an unconscious source of disturbance, i.e., as matter. B similarly deduces matter, A, from the interaction with A’s stream of consciousness.

Each is aware of many such external realities and these are perceived to have interactions with each other which can be arranged in a coordinate system consisting of two dimensions of direction in addition to one of remoteness. The order of succession of events provides a fourth dimension, time.

In certain cases, the behavior of external matter is of such a nature as to indicate the presence of a stream of consciousness, another mind, with which varying degrees of communication become possible. In still other cases, the external reality parallels the internal so completely as to compel identification as a peripheral aspect of the observer himself, his own body. In most eases, however, there is no indication of any mind and the objective world thus seems to consist largely of mindless matter.

Under the dual-aspect view, the objective world of natural science with its hierarchies of physical and biological entities must exactly parallel an inner world of mind. Because of the flowing character of the latter, parallelism should be sought not in matter as mere mass and occupation of space, but rather in the incessant action which modern physics finds in its units; the wavelike properties of proteins, neutrons and electrons, photons and its other elementary entities, down to Planck’s quanta as the ultimate known units of action. At a higher level is the incessant action within molecules, including nucleic acid and protein. The metabolic activities within a cell, and its activities in relation to other cells may be considered the external aspects of the cell’s stream of consciousness. Introspection throws some light on the matter in the case of the multicellular organism. My own stream of consciousness obviously includes that of only a minute portion of my cells at any time. In a considerable part of the time (in dreamless sleep) it does not exist, although the cells continue their activities. When it does exist, it focuses now on one thing, now on another, the external aspects of which are the integrated activities of different but overlapping sets of cortical neurons which come successfully into dominance. That there is any unity in the stream of consciousness indicates that those of separate cells fuse. They cannot be the windowless monads of Leibniz.

The store of memory, carried along out of mind in ways that are the object of active research, undoubtedly contributes most, by activation of its components, to the unification, except in the rare cases in which two independent stores are built up, giving the basis for dominance at different times of one or the other of two personalities.

When we pass to the next higher step in the biologic hierarchy, the social organism, we at once perceive a difficulty. We speak of the ‘spirit of America,’ but it is difficult to think of this as anything but a figure of speech. It can, indeed, exist only as a feeling of consensus in the minds of separate individuals.

Choice and Determinism

Subjectively, mind seems to involve the continual exercise of choice, always of course within a limited range of possibilities. How is this freedom to be reconciled with the apparent determinism of natural science? Part of the answer is, already noted, that the laws of nature are ultimately statistical and no more preclude choice on the part of individual components than do statistical laws of human behavior.

There could not be statistical regularity, however, without at least some regularity in the behavior of individuals. Freedom of the will is sometimes treated as if it were equivalent to caprice, but mere chance is as little characteristic of free choice as absolute determinism. If one situation is much like another, the choice of the best course of action is likely to be the same. Apparent determinism along a chain of cause and effect may be looked upon as the external aspect of a sequence of choices.

It is to be noted that physics itself has had to abandon Laplace’s concept of absolute determinism since Pearson wrote the Grammar of Science. Because of Heisenberg’s principle of indeterminacy, physical science has had to arrive at statistical mechanics as its ultimate form of statement.

This still leaves the question as to how the larger organisms can behave other than by statistical laws which should simulate complete determinism with the utmost precision because of the large number of elementary components (some 1032 protons and neutrons). It is, however, of the essence of an organism (as of a man-made machine) that it contains numerous switch or trigger mechanisms which bypass purely statistical behavior. I like an illustration of this which I used in a class discussion in May, 1927, a day or two after Lindberg’s flight across the Atlantic, which seemed almost as sensational an achievement then as the first flight to the moon a few years ago.

It was a rather remarkable phenomenon from a purely physical standpoint when a great mass of material rose from the ground in Long Island, moved steadily in spite of buffeting winds across the Atlantic and finally settled down gently at the Paris Airport. Yet if an engineer could have studied the air pressures on wings, cabin and ailerons (the movements a the latter under control of the lever), the motion of the propellers, the mechanical connections of these to the motor, and the gas explosions in the latter, he would have found that the plane was merely following a necessary course, determined at all moments by well-established physical principles -- except that this would not account for the motions of the levers. This, however, would have involved only an infinitesimal portion of the total energy transactions.

A physiologist, taking up the analysis at this point, would find that the levers moved as they did because of a certain succession of muscle contractions in the pilot’s arm. He might trace the energy transactions in the latter in full detail to the consumption of a certain amount of glucose and find that they were strictly in accord with the conservation of energy, except that he might not understand why there was a particular succession of stimuli from neuromuscular junctions. Another physiologist would find that these were controlled by a chain of neurons from the brain connected by synapses. The energy transactions are here infinitesimal compared with those in muscles, but again have been shown to be in accord with the conservation of energy. He might not understand just what happened in the synapses which determined which neurons were activated, but would find that only an infinitesimal amount of the energy of the nerve currents was involved. The flight of the plane would be fully accounted for deterministically except for the product of a succession of infinitesimals. Yet the whole was according to Lindberg’s plan.

A high degree of freedom of choice by the whole is thus consistent with apparent deterministic behavior of the parts. This is very different from control of the whole by minute indeterminacies, something that is prevented by self-regulatory processes.

Respect for the choices of the entities at all levels in the hierarchy does set limits to the freedom of each. The dual-aspect hypothesis implies that each event depends 100 percent on choice as the inner aspect of physical causation, but, with the whole history of the universe converging on it, it depends on the resolution of the choices of all entities at all levels in the hierarchy. The whole can dominate only in ways that involve concurrence of the parts.

Clifford and Pearson

As I have noted, I arrived at this dual-aspect panpsychism in 1914 after reading Pearson’s Grammar of Science and Moore’s Origin and Nature of Life. I was surprised after looking into these books for the first time in 60 years to find that I had not taken this philosophic position directly from either author. Pearson did, however, insist that the field of science is the contents of the minds of normal observers, not the things themselves. He said:

Immediate sense-impressions form permanent impressions in the brain which psychically correspond to memory. The union of immediate sense-impressions with associated stored impressions leads to the formation of ‘constructs’ which we project ‘outside ourselves’ and term phenomena. The real world lies for us in such constructs, not in the shadowy things-in-themselves. . . . These are the facts of science and its field is essentially the contents of the mind. It (scientific law) is a brief description in mental shorthand of as wide a range as possible of our sense impressions.

Pearson’s definition of consciousness differs from mine:

When an interval elapses between sense-impression and exertion, filled by cerebral activity marking the revival and combination of past sense impressions stored as impressions, we are said to think or to be conscious. . . . Consciousness has no meaning beyond nervous systems akin to our own.

Pearson thus did not consider mere instantaneous awareness of a sensation as consciousness. He included decision making in consciousness but considered its apparent freedom a delusion.

With respect to metaphysics he wrote:

The concepts of the metaphysicians, Kant’s thing-in-itself or Clifford’s ‘mind stuff are in my sense of the words unreal. They cannot become immediate sense impressions.

Obviously I did not derive the concept of dual-aspect panpsychism directly from Pearson. There is also no suggestion of it in Moore. It was however, the ideas which I derived from them that led me to it in 1914.

The first reference to this viewpoint, which I encountered later, was in a paper by Troland (1922), who presented it very clearly and referred to a number of earlier presentations going back to Fechner in 1863 and included Clifford (1879), which I then read and found a very clear presentation. Pearson (who had edited a posthumous volume of Clifford’s mathematical papers) fully accepted Clifford’s concept of matter and of physical phenomena, frequently using the term ‘construct’ (which he credited to Clifford), but rejected his monistic concept (without giving any exposition beyond the vague reference to "Clifford’s ‘mind stuff,’" quoted above). This reference did not tempt me in 1914 to look up Clifford, but I evidently reconstructed his position from what Pearson did accept of his views on matter, as more acceptable to me than Pearson’s. Pearson seems to have derived his philosophy of science largely from Clifford but left out the keystone. After taking the Grammar of Science back to the library and reading Moore’s book and mulling over them, I seem to have put Clifford’s keystone in place without realizing that Pearson had rejected it.

My purpose, and I presume that of all others who have approached the subject from the scientific side, has been to find a metaphysics which, with the minimum of speculation, finds a place for the obviously primary reality of the stream of consciousness, while fully accepting the findings of science. Those who have reached a similar conclusion on the primacy of mind, but from the viewpoint of philosophy, such as Whitehead (1925) and Hartshorne (1942, 1954), have built up more elaborate metaphysical systems.

This difference in aim has led to some divergence in dealing with the Universe as the world of mind, within which all subordinate minds must be included in some sense, from either point of view. The question is whether, at one extreme, the mind of the Universe is all-knowing and omnipotent, or at the other, it is merely that which is superimposed on the point-to-point interactions of the minds of the components as the integrating factor, in much the same relation as that of my mind to the minds of my cells and lower entities in the hierarchy of existence. As one concerned with the philosophy of science rather than philosophy in general, I must take the latter view, recognizing that there is a great deal that science does not and probably never will know.

When the astronomers tell us that it requires more than a billion years for a message to pass from certain observed objects to our galaxy at the maximum velocity accepted by physics (3x 1010 cm/sec.) and that, apart from this, there is integration only by universal gravitation, the universe seems rather loosely integrated. It is possible that my time scale is too infinitesimal to recognize organization on a cosmic scale, but here I am disturbed by the big-bang theory of cosmology. If the universe, as we know it, is exploding and has been doing so for only a moderate number of billions of years, after a condensed phase in which all prior organization must have been obliterated, the likelihood of a high state of organization as a whole seems small indeed.

The astronomers do not, however, appear to have reached definitive views on cosmology. Perhaps there was no big bang. Perhaps there are means of communication vastly more rapid than the velocity of light. A philosophy of science must, however, restrict itself to interpretations based on the current findings of science with the caveat that these are certain to change in ways which we cannot predict.

Science and Philosophy

Finally, what differences in the methodology of science are suggested by adoption of dual-aspect panpsychism in place of determinism? I fully agree with Pearson here that science is restricted to verifiable knowledge and thus must exclude the knowledge of our streams of consciousness, because it is unverifiable by anyone else. We must continue to accept a rigorous determinism as far as possible, and supplement this by probability distributions where necessary, even though we interpret the determinism philosophically as the external aspect of choices throughout the hierarchy of existence and make use of this philosophical interpretation in choosing topics for research. Some use of subjective terms may be warranted in describing the behavior of human beings and perhaps of higher animals to avoid ponderous circumlocutions, but should be avoided in attempts at the most precise formulations. I stated this emphatically in the first paper in which I indicated my philosophical position, a review (1921) of a book by C. M. Child on The Origin and Development of the Nervous System:

The theory, as a mechanistic one, seems the very antithesis of such views as those set forth by Driesch with his quasi-intellectual factor, the entelechy, as the guiding spirit of development, and by Bergson with his elan vital. In a sense, however, there is a curious approach. Under Child’s theory there is complete continuity from the reaction of the cell with its environment, which constitutes the primary metabolic gradient, and from the later reactions, by which the pattern of the developing embryo is laid down in accordance with the changing gradient pattern, to the intellectual processes by which the adult organism adjusts its relations to the outside world. Since awareness is certainly associated with the dominating nervous activities in the latter case, it seems necessary to grant the possibility of its presence in the former unless we wish to assume that it is arbitrarily superimposed upon metabolic gradients at a certain level of complexity. Moreover as a state of consciousness in the higher case is certainly closer to reality than any impressions which it may make on other consciousness the question at least seems open as to whether the entelechy may not be the reality of which the metabolic gradient, however much correlated with environmental factors, is merely the outward show. However this may be, it does not, of course, detract at all from the vastly greater significance to science of such a conception as that which Child presents.

I took the same attitude on the roles of science and philosophy in my first major paper on evolution in 1931. In this paper, I tried to interpret evolution as a continually shifting balance, spatially and temporally, among what I called the pressures of mutation, selection, and migration on gene frequencies, in conjunction with the effects of random drift composed of random variations in these pressures and of local accidents of sampling. These provide material for inter-group selection at a level, the interaction system, higher than that provided for by mass selection of individual mutations. There was no reference to any role of mind except in a paragraph immediately before the summary in which I indicated both my philosophic position and what I considered the necessity for restriction to deterministic and probabilistic statements in a scientific treatment. I would like to cite this paragraph which has continued to be my position in many papers on the subject:

The present discussion has dealt with the problem of evolution as one depending wholly on mechanisms and chance. In recent years, there has been some tendency to revert to more or less mystical conceptions revolving about such phrases as ‘emergent evolution’ and ‘creative evolution.’ The writer must confess to a certain sympathy with such viewpoints philosophically, but feels that they can have no place in an attempt of scientific analysis of the problem. One may recognize that the only reality directly experienced is that of mind, including choice; that mechanism is merely a term for regular behavior, and that there can be no ultimate explanation in terms of mechanism -- merely analytic description. Such a description, however, is the essential task of science and because of these very considerations, objective and subjective terms cannot be used in the same description without something like 100 percent duplication. Whatever incompleteness is involved in scientific analysis, applies to the simplest problems of mechanics as well as to evolution. It is present in most aggravated form, perhaps in the development and behavior of individual organisms, but even here there seems to be no necessary limit (short of quantum phenomena) to the extent to which mechanistic analysis may be carried. An organism appears to be a system linked up in such a way through chains of trigger mechanisms that a high degree of freedom of behavior as a whole merely requires departures from regularity of behavior among the ultimate parts of the order of infinitesimals raised to powers as high as the lengths of the above chains. This view implies considerable limitations on the synthetic phases of science, but in any case it seems to have reached the point of demonstration in the field of quantum physics, that prediction can be expressed only in terms of probabilities, decreasing with the period of time. As to evolution, its entities, species and ecologic systems, are much less closely knit than individual organisms. One may conceive of the process as involving freedom, most readily traceable in the factor called here individual adaptability. This, however, is a subjective interpretation and can have no place in the objective scientific analysis of the problem.

I would now write ‘individual selection’ and ‘selective diffusion’ in place of ‘individual adaptability’ as referring to coefficients which are actually used in the mathematical formulation but which nevertheless represent processes which may involve choices made by individual organisms. Otherwise this quotation reflects my position in this and all later papers on the subject.

No doubt Pearson was correct in feeling some danger to science in accepting a philosophy of science which recognizes choice as real, but I do not think that this is serious if it is also recognized that determinism is necessarily the external aspect of the chains of choices at all levels. There is also a danger of which I think Pearson was not sufficiently aware in being satisfied with a statistical description as ultimate. This may lead to premature abandonment of analysis in cases in which analysis could be pushed further by one who believes firmly that there is a deterministic mechanism to be found. The remedy is a clear recognition of the danger and a lively interest in carrying analysis as far as possible up and down the hierarchy of being.

Pearson undoubtedly felt more satisfied with a merely statistical account of resemblance’s of individuals to their parents and more remote ancestors than did geneticists with a deterministic metaphysics. He violently opposed the Mendelian analysis of heredity after its rediscovery in 1900. The latter indeed is also statistical. The geneticists, however, were not satisfied with merely enunciating laws of heredity. They looked on the latter as indicative of real entities and became concerned with where they were in the cells and what they did. Geneticists passed from the formal genetics of individuals to cytogenetics at the cellular level, to the biochemistry of DNA in duplication and in protein synthesis at the molecular level, back to physiological and developmental genetics again at the cellular level and back to the level of the individual in behavioral genetics and beyond the individual to population genetics and the theory of evolution. All have been pursued rigorously from the external deterministic and probabilistic standpoints. This process is, I think, a necessary precursor of any attempt at a philosophical interpretation.

There is also the opposite danger that failure to accept the reality of choice, a fatalistic acceptance of absolute determinism, may lead to such slackening of individual and social effort as to bring about the end of civilization.

My final conclusion is that there is real satisfaction in a philosophy which can bring under a common viewpoint the vast body of secondary but verifiable knowledge of the external world which constitutes science, with its necessarily deterministic and probabilistic interpretations, and the primary but private knowledge which each of us has of his own stream of consciousness, more or less continually directed toward the finding of an acceptable course through the difficulties of the external world by means of voluntary actions.


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Wright, S. 1948. "Evolution, Organic." Encycl. Brit. 8:915-929.

Wright, S. 1953. "Gene and Organisms." Amer. Nat. 87:5-18.

Wright, 5. 1964. "Biology and the Philosophy of Science." The Monist 48:265-290. Also in Reese, W.L. and Freeman, E. (eds.), Process and Divinity: The Hartshorne Festschrift, pp. 101-125. La Salle, Illinois: Open Court Pub. Co., 1964.