Psychology, Natural Science, and Philosophy

Creighton, J. E. “Experience and Thought.” The Philosophical Review 15, no. 5 (1906): 482.

ORIGINALLY, before the division of labor, the kingdom of knowledge formed an undivided whole, and philosophy was monarch of all she surveyed. In the course of time different fields of study were marked off, but the unity of the whole was not lost sight of. Philosophy remained the mother science for more than two thousand years, and the special sciences that sprang up came within the sphere of her influence. The Greek and mediaeval philosophers knew all that was known in the theoretical domain, and even a Christian Wolff felt competent to lecture on physics, mathematics, and political science in addition to psychology, logic, ethics, and metaphysics; while Kant was willing to accept almost any chair in the faculty of philosophy except the professorship of poetry, which, all will agree, he very wisely declined.

But in our day, all that has changed. The labor has been divided and subdivided until at present the individual worker hardly dares to claim a knowledge of anything but the narrowest strip in the field of truth, and the college professor, who was formerly a jack of all trades, now modestly confesses that he is master of none. The world has been chopped into little bits and each investigator must see to it that he leaves his fragment of reality smaller than he found it. Philosophy, the sometime queen, has become a dowager; her children have deserted her, all but a few barren daughters, we are often told, for whom nobody cares. The only members of the original household left are psychology, logic, aesthetics, ethics, epistemology, and metaphysics, a paltry remnant of a once brilliant and numerous crew.

And now the demand is frequently heard that psychology too cut loose from her old-fashioned sisters and set up an establishment of her own or go to live with the natural sciences. The motives for this demand are various. The introduction of laboratory methods into psychology has given it a scientific savor, and the experimentalists are often ashamed of the company they are forced to keep. They have greater respect for the kind of work done by the natural scientists, who are apt to smile at the pretensions of the philosophers and are therefore eager to flock with them. Or it is held that psychology is itself a natural science and belongs by right to that field. Mental processes cannot be understood without a knowledge of their physical and biological environment and must therefore be given over to men trained in these lines of research. Or the reasons for separation may be of a more practical nature. The psychologists may complain that the philosophers do not sympathize with their aims, that they do not comprehend their needs, and that association with them is apt to be detrimental to their interests. And here and there a philosopher may argue in favor of expelling empirical psychology, or at least psychophysics, from the philosophical union for similar reasons or because the expense of establishing laboratories should be borne by the scientific departments.

The proposed separation, however, would, in my opinion, be beneficial neither to philosophy nor to psychology itself. The affiliation is to the advantage of both parties. Of course, the relation between these branches of knowledge is not to be one of absolute dependence on either side. By no means is psychology to be the handmaiden of metaphysics; the purpose cannot be to neglect the facts of mental experience and to offer a prior system of psychology. Psychology must do its work along the general lines marked out for it in modern times, and continue to enjoy the independence which it has achieved within the domain of philosophy, and which, so far as I can see, no one dreams of curtailing. But independence here is not identical with disunion or even affiliation with another power. There are cogent reasons against such a change, and these I shall attempt to outline in what follows.

In the first place, we may argue against the affiliation of psychology with natural science on the ground that the subject matter of the former differs from that of the latter. Whatever may be the ultimate essence of matter and mind there is difference enough between them to justify the distinction which has come to be made between mental and physical processes and has led to the development of two groups of sciences, the mental and the natural. The science of psychology is primarily interested in thoughts, feelings, and volitions, natural science, in material objects. As Professor Munsterberg says: “Psychology examines no body when it analyzes the ideas of bodies, physics examines no ideas when it analyzes the perceived body." These thoughts, feelings, and volitions form a more or less connected series of events, a domain in which we can discover law and order and are therefore capable of scientific treatment. It is because such an orderly body of unique facts exists that a special science called psychology has grown up and is possible. Now the other philosophical branches, logic, aesthetics, ethics, the theory of knowledge, and metaphysics are likewise fundamentally interested in the mind, and their affiliation with the science of mind is therefore not only historically but logically justifiable.

It is true, the facts of mental life do not appear in isolation but are somehow related to a physical and biological environment. Hence, they may be studied in connection with the occurrences which constitute the special subject matter of the natural scientist. Here the ideal will be to discover the particular material processes with which particular psychic states are connected. But in psychology the interest will always be centered upon mind; the facts of physics and biology will be drawn upon simply in order to throw light upon the inner world. The interest of the natural scientist, on the other hand, is directed toward external nature, and he refers to the inner world only when a proper understanding of this will aid him in understanding the ways of matter. For ages and ages, down through the mediaeval period, he believed that mind or soul alone could explain animal or human movements, and therefore introduced it as a principle of explanation. When he felt able to account for all physical occurrences without having recourse to anything mental, he abandoned the principle and ignored mind as lying wholly outside his sphere.

The fact, however, that mental states can be studied in connection with matter does not make psychology a branch of physics or biology, any more than it makes the latter a branch of the former. A perfect knowledge of the physical and physiological counterparts of mind would not give us a knowledge of the mind as such. Even if we could tell all about the brain and what takes place inside and outside of it, we should never come face to face with a thought or a feeling in this field, for a thought our feeling is quite different from a molecular motion in the brain or anywhere else. "The most accurate knowledge of the processes in the nerve substance could not give us an idea of the corresponding psychical facts if we did not possess it otherwise." The physiologist, limiting himself to a study of the brain, would, to quote Professor Jodl, known as little of mind as a deaf and dumb man would know of music by studying the score of a musical composition. So long as there are thoughts and feelings and volitions, and so long as these can be reduced to law, there will be room for a specific science with the business of studying these phenomena in its own way. Whether the physiologist regards the mind as a principle of explanation, as he once did, and explains all animal and human movements by means of it, whether he casts it aside as useless for his purposes and seeks to reduce all such activity to brain machinery, or whether he makes consciousness a by-product of the brain to be accounted for mechanically, his chief interest lies in the domain of matter, while “the distinctive aim of the psychologist is," as Professor Stout says "to investigate mental events themselves, not their mechanical accompaniments or antecedents." Call mind what you please, call it an effect or another aspect of matter, call it a distinct principle or entity alongside of matter, or a manifestation of something behind them both, call it the sole reality and matter its appearance, it is a unique fact and deserves to be investigated as such. You can ignore it if you choose; you can decide to pay attention only to its material accompaniments and antecedents, but you cannot do this and be a psychologist.

But, says an objector, the physiological processes are, after all, the real things, and the mental states are dependent on them. The real causes are the brain operations. Hence knowledge of brain action is real scientific knowledge. It is the business of the scientific thinker to explain these states of consciousness by referring them to their causes just as he explains sound and light. Colors and tones are the effects of ether and air waves respectively, ether and air waves are not the effects of colors and tones. Similarly, states of consciousness are explained by, but do not explain, brain states. The ideal of the physiologist must therefore be what Exner conceives it to be: "I regard it as my task," he declares, “to explain the most important psychic phenomena by degrees in the excitations of nerves and nerve centers, hence, to reduce everything in consciousness that appears to us as a manifoldness to quantitative relations and different connections in otherwise essentially homogeneous nerves and centers." This view represents the climax of the mechanical theory of the world, which, after having conquered the inorganic realm and laying claim to the organic sphere, now proposes to take possession of the mind as the natural appendage of the latter.

Disguise it as we may, however, this argument rests upon the questionable metaphysics of materialism. If it were true and the ideal held up were realized, psychology would in a certain sense play second fiddle to physiology. So would logic and ethics, political and social science, history, and philology; all would find their ultimate explanation in the mechanics of the brain. Physiology in turn would be reduced to physics; physics would be the mother science, and we should be back again in metaphysics.

And still there would be room for psychology. The psychologist would keep right on studying the so-called effects of brain action, the states of consciousness; he would seek to analyze and describe them and discover the order that is in them. However, complete our knowledge of the brain motions might be, this would not tell the whole story; indeed, it would not touch the real problem of psychology at all. Only in case there were no states of consciousness, or if they could not be reduced to any form of law, if there were neither rhyme nor reason in them, would psychology, as we have conceived, it find its occupation gone. There would be no science of psychology to affiliate with the natural sciences; it would have about as much standing in court as a science of augury. "Wo nichts ist hat der Kaiser sein Recht verloren."

The ideal, however, is far from realized. We possess no such astronomical knowledge of the occurrences in the nervous systems is here dreamed of. Our knowledge of the processes on which the elementary forms of psychic life are said to depend is far from certain, exact, and complete; while of the higher forms of mind we have no physiological knowledge worth speaking of, so little indeed as to prompt physiologists themselves to deny the existence of a science of cerebral psychology. “It would of course be a great triumph," Du Bois-Reymond once said, "if we could say that a particular motion of particular atoms takes place in particular ganglionic cells and nerve fibers corresponding to a particular mental process. It would be immensely interesting if we could turn the gaze inward and watch the operations of the brain mechanism that is going on when we are working out a problem in arithmetic, just as we can watch the mechanism in an adding machine, or even if we knew what dancing’s of atoms of carbon, hydrogen, nitrogen, phosphorus, and other elements corresponded to the joy of musical sensation, what whirlings of such atoms corresponded to the highest pitch of the pleasures of sense, what molecular storms accompanied the maddening pain occasioned by injury to the nervus trigeminus. . .. At present we do not even know whether only the gray matter or also the white matter of the brain thinks, or whether a definite configuration or a definite movement of brain atoms or molecules corresponds to a particular soul state."

Here we are forced to speak, for the most part, in figures of speech. We do not know what is going on in the brain, we do not even know that all mental states have their physiological counterparts. We can form hypotheses concerning what is happening, but let it be remembered, these hypotheses cannot be formed without due regard to the thought world which they undertake to explain. If the phenomena of consciousness are the symptoms of hidden brain action, it would seem rational to study the symptoms in order to get at the underlying causes; indeed, that would seem the only possible way. In short, the brain physiologist cannot take a step in the construction of his hypotheses without a knowledge of mind, that is, psychology. If his psychology be crude, his brain theories will be crude: they must needs conform to his psychological beliefs. One of the most glaring examples of this truth is the theory of phrenology. To quote from Professor Hoffding's recent book on the Problems of Philosophy; "If it is desired to supersede psychological definitions by physiological, it is evidently presupposed that psychological definitions are already in existence. The creation of these definitions must be the part of psychology; and if it can itself make no clear-cut definitions, assuredly physiology cannot ascertain for what it should seek in the brain an explanation for. If what is to be superseded be vague and uncertain, then what supersedes it will likewise be vague and uncertain. And we cannot derive certainty from the fact that we have actually discovered the brain states which correspond to psychical manifestations observed in the act. The independence of psychology must be recognized in any event since it prescribes like a kind of symptomatology the work of physiology. It is a long and difficult task to find adequate definitions in any experimental science; they only become possible when the science has actually reached completeness; they come at the end, not at the beginning of the investigation. Only too often have crude psychological definitions been considered trustworthy starting points for the investigations of brain physiology."

If, however, our knowledge of the physiological causes were so profound that we could deduce from them their psychical effects without paying any attention to the mental processes as we now do in psychology, then indeed the physiologist could afford to ignore psychology. But there would still remain another way of studying the mind, a more direct way, in which we should come face to face with the states deduced by the scientist, and this too would be interesting if only as an experimental verification of the results of brain physiology. In the meanwhile, there is no such science as is here spoken of, and it would be unreasonable to ask us to postpone the consideration of the problems of logic, ethics, can deduce them from the mechanics of the brain. Professor Stout is right: "Such a demand is logically parallel to a demand that history or biography, or the practical estimation of character and anticipation of men's actions in ordinary life; shall come to a standstill until they have a sufficient physiological basis. On this view Carlyle should have abstained from writing his French Revolution, because he did not know what precise configuration and motion of brain particles determined the actions of the mob who stormed the Bastille."

We have said that so long as there is coherence in the mental world, uniformity of coexistence and sequence, psychology will have work to do. But the objection is urged, the mental series does not form a continuous line, there are breaches in it, and you cannot therefore explain mental states by themselves. Unless you are willing to assume creation out of nothing, you must get physiology for help. In the one case, you have no science at all; in the other, it becomes a branch of natural science. Not only can no uniformity be discovered in the psychical realm, there can be none in the very nature of things. For the cortical processes depend on the subcortical processes; therefore, the excitations in the cortex do not form an unbroken causal series, because many of their causes lie in the subcortical region. And hence, since the subcortical activities are not accompanied by consciousness, the conscious processes of the cortex must show gaps. The mental world, in other words, does not form an unbroken causal nexus and cannot be understood without reference to matter. In external nature alone can there be a closed causal chain, here alone can there be true science. In order to be scientific, psychology must become physiology.

The following answer may be given to this argument. The appeal of one science to another for aid is not equivalent to a surrender of its autonomy. By referring certain mental phenomena to their physical conditions or concomitants, psychology does not become merged in or subordinated to physiology. Moreover, the fact that our knowledge of the psychic line is broken does not prove that the line itself is broken. More careful observation may lead to the discovery of the missing links. And where observation leaves us in the lurch, we can have recourse to hypotheses, and here it is to be noted that the physiological hypothesis is not the only possibility. Besides, our knowledge of the physiological chain is not continuous either; here too there are gaps, or here too the gaps are bridged over by theory. The physiologist simply assumes continuity; his fundamental hypothesis is that there can be no gaps in the material world. Formerly he had recourse to animal spirits, vital force, and soul to fallout the gaps, and even to-day many scientists refuse to rest content with the purely mechanical theory of the world. Finally, if there is not a certain amount of discoverable uniformity on the mental side, the physiologist has no clue to the study of the brain processes upon which the phenomena are said to depend. If there is no coherence or order in the effects, how can there be coherence or order among the causes? If psychology is impossible because there is no law on the mental side, then cerebral physiology is impossible because there is no law on the physiological side, and also because we have no key with which to open the secrets of the brain.

The argument is often made in favor of affiliating psychology with natural science on the score of the method. Psychology, it is held, must investigate its facts as the natural sciences investigate theirs, by the methods of observation and experiment. It must also measure its phenomena or apply the method of numerical determination wherever this is possible. The methods of observation, experiment, and measurement are the methods of science, their employment is what makes a science exact, and presupposes thorough scientific training on the part of those whose them. Psychology is therefore a natural science and belongs in that field.

This reasoning does not seem to me to hold good. True, the general method of psychology is the same as that of every other department of research; the psychologist seeks knowledge and must employ all possible methods of knowledge in order to realize his purpose. Of course, it is logically possible to make the empirical method the principle of union and to subsume all sciences employing it under one head. But that would be a superficial arrangement, neglecting, as it does, very important differences. There is a specific difference between the method of psychology and that of natural science. The method of psychology is primarily subjective or introspective, the method of science is objective. The psychologist studies the facts of a thinner world, the physicist and physiologist those of the outer. The fields of study are different and the ways of handling them are different in this specific sense. It is true the psychologist also uses the objective method, he pays attention to physical antecedents and accompaniments of mind, but his chief interest lies in consciousness; for the sake of this he regards the physical world. Even when he is occupied with the child and animal mind, introspection forms his basis and his guide. Only in case introspection is ruled out as worthless will this view fail, but in that event, there can be no science of psychology, at least not in the sense in which this term has been understood down to the present time.

The introduction of the experimental method into psychology does not change this relation. It does not aim to do away with introspection; its object is rather to facilitate introspection, to render it more exact, to correct it, to bring it under control, to verify it. And as for measurement in psychology, well, we do not really measure mental states, but their physical concomitants. Besides, the measurement of the physical counterparts’ forms but a small and unimportant part of the problem of psychology. More or less exact numerical determination of this kind is possible only on the borderline of physics and psychology; only physical stimuli can be quantitatively determined, and such quantitative determination does not throw much lighten the real problems of psychology. It is due to the appreciation of this fact that the trend toward psychophysics which characterized the beginnings of experimental psychology has been interrupted. "It is not at all surprising," says Professor Wundt, who certainly speaks with authority in this field, “that psychology, which has become an independent discipline only within comparatively recent years," "should be mainly occupied with elementary problems, with problems largely to be found on the boundary line between physiological and psychological research, but it goes without saying that its final vocation must not be determined by its present status." And Professor Titchener declared in his address before the Congress at St. Louis: “You know without my telling you . . . that the course of experimental psychology in recent years has been away from simple numerical determinations, and towards introspective analysis; and that. the experimental method has been continually extended from the simpler processes to the more complex, whether to complexes hitherto untouched, by experiment, or to unfamiliar phases of familiar mental formations." "I have little sympathy or patience with those experimentalists who would build up an experimental psychology out of psychophysics and logic; who throw stimuli into the organism, take reactions out, and then, from some change in the nature of the reactions, infer the fact of a change in consciousness. Why in the world should one argue and infer when consciousness itself is there, always there, waiting to be interrogated? This is but a penny in the slot sort of science. Compared with introspective psychology, it is quick, it is easy, it is often showy. We have been a little bit corrupted by the early interest in psychophysics, or, perhaps more truly, we have not all learned instinctively to distinguish between psychophysics and psychology proper, and so we are apt to take the tables and curves of reactions for psychological results, and the inferences from them for psychological laws. Now the results, where they are not purely physiological or anthropometrical, are psychophysical results. As such they have their usefulness; and the psychological laboratory is their right place of origin. But there is no reason why one should gain psychological credit for them still less for erecting a speculative psychology upon their foundation."

My conclusion, therefore, is that psychology is not a natural science either in subject matter or in method, and that there is no reason for affiliating it with natural science. Its task is to study the facts of mental life, and its fundamental method is that of introspection. Now it is conceivable, of course, that it should cut loose from its historical association with philosophy and proclaim its independence. But there is no good reason why this should be done. Indeed, it is to the interest of both parties that the old friendly relations be continued. Philosophy needs the companionship and example of psychology to do fruitful work, and psychology cannot fail to benefit by such association herself.

By philosophy we here mean the subjects taught under that name by the philosophical departments of our universities, logic, aesthetics, ethics, epistemology, and metaphysics. All these are mental sciences, all are primarily concerned with mind. Psychology is indispensable to these fields of investigation, so indispensable that many writers have been tempted to regard them all as branches of psychology. Though they are not that, psychology may be said to hold the key to the situation. Not one of them can neglect psychology with impunity. Logic, aesthetics, ethics, and the theory of knowledge are interested in mind, and it is essential that they understand the mind. And metaphysics, though it is interested in all the facts of existence, in the physical as well as the mental realms, has a particularly vital interest in the inner world. Its concepts, methods, ideals, and evaluations are products of the human mind, and it must reckon with the source from which they spring. All these subjects are so intimately bound up with psychology that separation would mutilate them all. The close relation existing between them has its practical consequences also. The students in a department of philosophy cannot afford to neglect the study of mental life: ignorance of psychology will make itself felt in the work of the related subjects. And the needs of the department would not be satisfied by courses in psychophysics and physiological psychology given by natural scientists. On the other hand, the aims and problems arising out of the philosophical disciplines help to give direction to psychology and thus influence it. The interest in logical, ethical, epistemological, and metaphysical problems arouses interest in certain phases of mind and leads to a psychological study of the same. (Perhaps we can partly explain the trend away from psychophysics also.) It fastens the attention on processes of mind which the natural scientist is apt to ignore because he can find nonphysical antecedents for them. Such philosophical study also acts as a safeguard against a false mental atomism and tends to keep view of the unity of mind. As these remarks apply with even greater force to metaphysics, the especial bugbear of some scientists, it may not be out of place to discuss this point a little further.

The relation of psychology to metaphysics is not to be conceived in the old-fashioned sense of an a priori construction of the facts of psychology from metaphysical principles. If the thing could be done, if the facts discovered by empirical psychology could be deduced from a few fundamental principles, without any regard to experience, there would be no objection whatsoever to doing it. But no system of metaphysics exists that can shake out of its sleeve all the mental phenomena with which we become acquainted through observation, and so far, as I known system has ever attempted such a thing. But if dependence on metaphysics means that psychology must start out with some broad assumptions or general principles, then psychology, like every other science, is metaphysical. To refuse to start out with any epistemological and metaphysical assumptions is not to start out at all. The only question here is with what assumptions to start out, and most of the trouble is due to the fact that one man’s assumptions are gall and wormwood to another. And often the psychologist is not conscious of having any assumptions, or his assumptions seem so self-evident to him that he takes them for what he is pleased to call facts, while his colleague’s presuppositions strike him as unwarranted metaphysical fictions. So enamored are we of our own pet notions! If, finally, the introduction of hypotheses makes psychology metaphysical, psychology cannot escape metaphysics; indeed, no science can. Psychology cannot get along without hypotheses; hypotheses are always in a certain sense confession of ignorance, and where we are ignorant there is nothing to do but to confess. Here, again, the quarrel is not so much about introducing hypotheses as about the kind of hypotheses introduced. Where we do not know we are forced to guess, and though one man’s guess is not as good as another's, there is usually room for difference of opinion. But one man's guess seems so plausible to him and so satisfactory, that he can see nothing in the other man’s, and he shows his contempt by calling the latter's metaphysical. The Germans define a professor as a person who does not agree with you. In the same way we might define a metaphysical theory as one which does not agree with our own. The physiologist, for example, insists that the introduction of certain hypotheses into psychology is metaphysical, and repudiates the kind of psychology that is guilty of such behavior. He will have nothing to do with soul or psychic dispositions or unconscious processes because these concepts are metaphysical. But the question here is simply, do these conceptions or theories really explain the facts? If they do not, they are to be rejected, not because they are metaphysical theories, but because they are inadequate theories. As a rule, the thinkers who proclaim such violent dislike for metaphysics are not so hostile to it as they say; their bark is worse than their bite. They simply repudiate certain kinds of metaphysics, the other fellow's; with their own system they are well pleased; for them it explains the facts and is a fact. A wise remark of Heinrich Hertz, a scientist of no mean repute, is in place here: "No problem," he says, "that makes any impression upon us can be disposed of by being designated as metaphysical; every thinking mind has, as such, needs which the natural scientist is in the habit of calling metaphysical."

The truth is we cannot advance very far into psychology without having metaphysical and epistemological problems thrust upon us. In this field more than in the natural scientific domain questions of a philosophical nature come up which cannot be brushed aside. By refusing to consider them or branding themes absurd the investigator does not silence them. Unconsciously he assumes some attitude toward them, which guides him all along the line. The questions are not always openly asked, but they are generally silently answered, and the answers are assumed further ado. All this becomes evident enough when we call to mind that the different psychologists accuse each other of being metaphysicians. The empirio-criticists, who claim to have escaped the contagion, flout Wundt as a metaphysician in psychology, and Wundt lays bare the metaphysical assumptions of the Kritika of Pure Experience. They are both right. There is not absolutely presuppositionless psychology, and there never will be such a psychology. The sooner we accept this fact and examine the presuppositions of our science, the less inclination will we show to break away from philosophy and join the ranks of the natural scientists.

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