The Present Status of the Problem of the Relation between Mind and Body
I AM not sure that the title of this paper conveys the proper idea of its contents. It might have been more correct to call it "The Ghost Theory of Animal Behavior." But that might have impressed the hearer as too sensational.
At the last meeting of the Psychological Association, during the discussion of the place of psychology in medical education, one of the speakers found it necessary to warn against including in the teaching of psychology a discussion of the problem of the relation of mind and body. Let me say at once that I hold, on the contrary, that the problem of the relation of mind and body is the chief one, if not the only one, for the adequate discussion of which the medical student should turn to psychology, for practically every other content of the modern science of psychology is available to him in his courses other than those going under the name of psychology. Yet in spite of the apparent contrast of opinion, as just stated, I feel certain that my own ideals are not essentially different from those of the gentleman referred to. The contrast of opinion results chiefly from the meaning of the phrase " relation of mind and body." I object to throwing the problem of the relation of mind and body out of the curriculum of a medical student just because some teachers of psychology can see in it no more than the endless repetition of traditional metaphysical speculation.
If we follow the traditions of past centuries, a discussion of the relation of mind and body is merely the discussion of metaphysical arguments in favor of adopting the one or the other of the two metaphysical war-cries, interaction or parallelism. I can readily understand why any one who expects of science, not terms suitable for shouting, but terms suitable for clearer and more comprehensive thinking, should get disgusted with these terms interaction and paral-
( 366) -lelism. If these terms mean anything to me, they mean this. Any mental state of mine, I am convinced on scientific, empirical grounds, is in a specially direct manner dependent on (mathematically speaking, is a function of) one or more variables of the nature of nervous activity. Suppose we refer to such mental and nervous variables as corresponding values. Then the question arises: Do such corresponding values make their appearance in our experience strictly simultaneously or in succession? In the latter case we have the relation of cause and effect; that is, we accept interaction. If, however, there is strict simultaneity, we can not speak of the relation of cause and effect; that is, we accept parallelism. Now, it is almost incomprehensible that philosophers should have wasted their energies for centuries in order to derive from metaphysical arguments an answer to a question which can be answered only by appealing to observation. Imagine that geographers had attempted to derive from metaphysical speculation an answer to the question whether the North Pole was located on the ocean or on a continent. They had to wait patiently until some one had made the observation. We shall have to wait patiently until an instrument (let us think of an X-ray mirror) will have been invented which enables a person having a mental state to observe the corresponding value, the corresponding objective process in his own nervous system without the slightest interference with the normal function of this nervous system. Then we shall be able to decide whether the corresponding experiences, subjective and objective, are strictly simultaneous or successive. Until then let us wait and not spend any more time on interaction and parallelism than what is sufficient to describe the problem to the student as a problem whose solution lies in the future.
With the rise of modern biological science parallelism seemed to be destined to beat its rival into oblivion. But a curious reaction has set in, and the latest book on this subject-matter, that of William McDougall ("Body and Mind") steps before the public eye as an outspoken and very able defender of interaction. What has brought about this evolution and attempt at revolution, for no name other than revolution seems to me significant enough for the attempt to answer our question thus one-sidedly? It might be said that the preceding parallelism was equally one-sided. As a matter of fact, this can not be said of the parallelism of that class of men whom we may compare with McDougall-of the biologists. With the biologists, especially those of the nineteenth century, the confession of parallelism did not mean the dogmatic solution of the problem which, as just stated, can be solved only by future observation; it really meant only a confession of their belief that animal life, including human life, in all its phases and. without any exception, could be
( 367) scientifically described without any reference whatsoever to subjective states, to states of consciousness. McDougall sees that this is the meaning of the term parallelism in the biology of the last centuries. He sees this so clearly that he defines his own view, interaction, as meaning that a scientific understanding of animal life is made possible only by introducing into the chain of causes and effects the subjective factor, consciousness.
Should we side with the majority of the biologists or with McDougall and those others of a similar trend who assure us of the insufficiency of a purely objective science of animal life? Before I give my answer, I invite you to glance back over a few thousand years of human thought. There was a time when no strange event seemed comprehensible to the human race unless it was referred to a god, a ghost, a demon as its source. Lightning was fire thrown by the weather god. A king eating grass did so because he was possessed of a demon. A friend found dead in his bed in the morning had been smitten by a ghost. We no longer think in this way. We no longer think of an epidemic, for example, as the work of gods taking revenge. Is not all progress of modern science due to the fact that scientists have consistently discarded all ghosts as causes explaining any natural phenomenon? And now we are asked to be inconsistent. In the explanation of animal, and especially human, life we are asked to introduce the ghost, consciousness, as a cause. Truly, before we take such an inconsistent step, strong proofs should be required that thereby we may hope to gain a scientific advantage.
Let no one object that introducing consciousness into the explanation of animal life, of animal behavior, is not the same as introducing a ghost into the explanation of an epidemic, for one's own consciousness is surely not an illusion. But here is the point: "one's own." The scientist who gives an explanatory description of an epidemic does not describe the disease from which he is suffering himself, lying on his death bed. He describes, if not exclusively, at least chiefly, his experience of the diseases which have stricken other people. And the scientist who portrays animal behavior describes chiefly his experience of the behavior of other organisms, not his own. But the consciousness of other organisms is not an experience. It is a ghost introduced for, the purpose of explanation like the ghost introduced for the purpose of explaining an epidemic.
What, now, are the scientific advantages which are offered us, if we show ourselves willing to deviate from the established custom of several centuries of scientific progress, if we show ourselves willing to introduce, in our study of animal behavior, the ghost into our explanations? Let me quote McDougall, whom I regard as the ablest champion of the "ghost theory" of animal behavior. He adopts for
( 368) this theory the name of "animism." He says: "Animism recommends itself because it points to a great unknown in which great discoveries still await the intrepid explorer, a vast region at whose mysteries we can hardly guess, but to which we can look forward with wonder and awe, and towards which we may go in a spirit of joyful adventure, confident in the knowledge that, though superstition is old, science is still young." I have been unable to find that McDougall claims for his view any other scientific advantage. I do not know how others estimate the weight of this one; to me it has no weight at all. I am too much aware of the present incompleteness of our neurological science, of the existence of a great unknown lying there before the intrepid explorer, too enthusiastic and hopeful in my endeavor to clear up my notions of the manner in which animal behavior depends on nervous functions, too much embued with the spirit of joyful adventure in the field of objective science---to turn to the ghost theory for a mental tonic, for inspiration and encouragement. If that is the whole scientific advantage offered by the ghost theory, I must say that I do not need it. Let him accept the ghost theory who has already despaired of further progress of the objective science of nature, who needs a bracing up. I do not need it.
If there is no real scientific advantage attaching to the ghost theory, how are we to understand its reawakening, under the name of interactionism or animism, among psychologists, after it had seemed, for many years, to have been laid into the grave with its last defender, Lotze? There are two reasons for this. First, it had suffered under an argument unjustly wielded against it. The assertion had been made and had been generally accepted that the theory was incompatible with the law of the conservation of energy. Fifteen years ago Stumpf succeeded in pricking this bubble. Unfortunately, however, some psychologists mistook the annihilation of that hostile argument for a positive proof of the value of the ghost theory, which, obviously, it could not be. The second reason is of greater significance. The neuron theory held its sway over neurology, and, as a part of this theory, appeared the doctrine of the synapse. The ear, say, is stimulated. A nervous process runs along a neuron, but only to find itself blocked at a point which is both an end point of the path thus far taken and a division point from which many directions may be taken. The tension becomes greater and greater. The protoplasm stretches out its arms like an amoeba and touches the protoplasm of another neuron. The nervous process then crosses this bridge. Thus far this seems plausible, and the doctrine of the synapse has always seemed plausible to the neurologist who asked no further question. Nut the psychologist asks a further and abso-
( 369) -lutely essential question: Why does the protoplasm stretch towards one neighboring neuron when the organism happens to be in one situation, towards another neuron when the organism is in another situation? General silence with the neurologists. But some psychologists had an answer ready. They brought in their deus ex machina. The ghost does it. Consciousness, feeling, will, or whatever you call it, turns the bridge in the proper direction as the switchman turns the switch in the railway yard. Thus the doctrine of the synapse is largely responsible for the reawakening of the ghost theory of animal behavior.
Although it does not interest us directly, I can not forbear mentioning as a curiosity the fine reasoning of some psychologists telling us that the mere causal determination, selection, of one direction among many thinkable ones did not require an expenditure of energy and therefore could well be regarded as the work of the ghost. As if the direction of anything, say, a pole losing its balance on the tip of the nose of a circus clown, could be causally determined without the expenditure of energy.
It was among European psychologists chiefly that the physiological doctrine of the synapse reintroduced the ghost into the explanation of animal behavior. In America the ghost became popular through the great influence of one man, James, whose followers assign to one kind of mental states which does not seem to have any proper business, to the feelings, the job of stamping in and stamping out complete paths of nervous conduction. But they never state any definite law explaining how the proper feeling itself, with its stamping power turned in the proper direction, comes into existence at the proper time.
We now reach the crucial point of the issue which I intend to present. According to McDougall, those who reject, or do not favor, the ghost theory of animal behavior do so because they lack the courage to accept an incomplete world picture. But I charge that, on the contrary, those who adopt the ghost theory lack the courage to accept an incomplete world picture and to wait for future research in natural science to complete it. Too impatient to wait, they fill in the gap with a ghost, with unexperienced consciousness, with the concept of something which is unmeasurable, to which none of the methods of scientific research are applicable. If any one claims that my assertion is wrong, that the methods of scientific research are applicable to the ghost which is made to bridge the gap of causal connections in animal behavior, I challenge him to state a single instance. Hewill not assert that such work as the classical experiments of Ebbinghaus on memory serves as such an instance. McDougall himself admits expressly that they are a purely objective
(370) study of verbal habits, that they are no measurements of consciousness.
How, then, did men, so much in earnest about psychological progress as McDougall, become so overwhelmed with despair that they had to appeal to the ghost theory for help, or rather for mere comfort? The answer is simple. They attempted in vain to conceive of a nervous process as being capable of forcing another nervous process from its own path into a new path. It is the demand for such a conception that I have tried to supply in my book on the "Fundamental Laws of Human Behavior."
The most important concept applied to animal behavior is that of an experience. We mean by an experience that an animal, in a new situation, acts in a new way in response to the same stimulus, that is, that the nervous process from a certain sensory point does not pass along the path of least resistance, but along a path of higher resistance. In order to understand that a nervous process proceeds over a path other than that of least resistance, we must speak of its being forced. But we need not speak of its being forced by a ghost. When a person, say, a school-boy, instead of moving along the path of least resistance, which leads to a, circus parade, is forced away from this path towards his school, he is forced most probably by another person, his mother, or a truant officer; but certainly not by a ghost, a good or evil demon. When a nervous process is forced to stream over a path other than that of least resistance, it is forced most probably by another nervous process. If psychologists had been less slow in thinking this simple thought, they would have been less quick in introducing the ghost who is supposed, in the nervous system, to take a place equivalent to that of a switchman of a railway yard, or a lineman of a telephone company, or a stamper of a sheet metal factory, but who, in the nervous system, is simply a deus ex machina. I have shown in my book that it is possible to understand all the fundamental facts of animal life experience by simply conceiving of any nervous process as capable of forcing, under certain conditions, any other nervous process out of the path of least resistance into another definite path. The doctrine of the synapse is then entirely superfluous. To enter into the details of this conception and its application to the various forms of animal (including human) behavior, this is neither the time nor the place.
If, then, a purely objective science of animal behavior must be the ideal towards which to strive to-day as much as, and even more than, at any previous period of science, can we afford to omit all reference to subjective states in the instruction given to scientific, and especially medical, students? May be that the time will come when we can afford it, but my study of the most modern advances in
( 371) that branch of medical science which particularly concerns us, in psychiatry, furnishes me sufficient proof that that time has not arrived yet. I have in mind that successful movement of studying and treating hysteria and related disturbances which has become associated with the name of the Austrian psychiater, Freud. His analysis of the individual's life leads to a systematic reeducation of the organism along definite lines, which is beginning to replace the former therapeutic methods of strong, but haphazard suggestions, hypnotic or non-hypnotic; and this analysis is made almost exclusively in subjective terms. It is too early, then, to renounce under any and all conditions all subjective terms in psychology. We can not put them out of the world by putting, like the proverbial ostrich, our heads in the sand so that we do not see them.
But then, certainly, it is impossible to keep the purely objective description of animal, or let me now rather say "human," behavior and its subjective description in tight compartments ; but a mixing up of them is equally unjustified. We need to establish definite relations between our subjective and our objective terms, so that, instead of mixing them up, we can translate the one into the other. Then only will it be possible to utilize the advances made at the present time in psychiatry for the advancement of an objective science of human behavior. We must try to establish definite nervous correlates for all the specific mental states and mental functions which are used in and seemingly can not he spared from our descriptions of human life in the mental and social sciences. I venture to predict that those terms of mental function, for which no nervous correlate can be found, are the very ones which are superfluous, can be spared from our descriptions of mental life in man and animals. When a few years ago I made an attempt at establishing some such nervous correlates, I found to my surprise that most psychologists did not seem to see the use of them. They failed to see the difference between such definite correlates and the vague generalities of our text-books stating that, whenever anything is to go on in our minds, something must go on in our brain; or that, whenever any brain, function is fixed, it is fixed by the satisfaction which it gives to the mind. Such generalities may be true; but to me it makes no practical difference whether they are true or not, because they are no solutions of scientific problems, for reasons stated throughout the whole length of this paper.
In the establishment of definite correlates of specific mental functions and of specific nervous functions I see the present-day problem of the relation of mind and body.
UNIVERSITY OF MISSOURI.