Against our view may be urged the fact that in proportion as a science tends to become exact, it takes on more a quantitative aspect, its phenomena are reduced to molecular or atomic changes. If now psychology is a science at all, it will reach its exactness, when it can be expressed in terms of matter and motion, so that the phenomena presented by consciousness, although at present impenetrable to our imperfect instruments and methods of investigation, must ultimately be reduced, in some way or other, to mechanical terms. Psychology has not yet had its Galileo.
This objection may be easily disposed of by the simple answer that the exactness of science is not at all in proportion to its degree of reduction to terms of matter and motion. No one will deny that mathematics is an exact science, but is it exact because it is reduced to mechanical terms? While mechanics must be logical, logic is not mechanical.
Within certain limits this generalization of the relation of scientific exactness to mechanical formulae may be fully granted, if it be restricted to the concrete physical sciences, but it cannot possibly hold good in case of psychology, as the latter does not fall within the circle of the physical sciences.
The weakness of this last objection from scientific exactness becomes clearly disclosed, if we get a little deeper into the matter. The reason why there is such a persistent tendency to reduce science to mechanical terms is based on the tacit understanding that atoms and motion are the only ultimate realities. We see at a glance that this consideration is at bottom purely metaphysical; it is a consideration which science has not to take into account. Nothing is so dogmatically metaphysical as just the common sense that has an abhorrence of metaphysics. That atoms and their motions are the only ultimate realities is certainly metaphysics and bad metaphysics too, as it is unguarded by reflective critical thought. Since this unreflective metaphysics of atomism is widely spread in the medical world, and is considered scientific, one cannot help discussing it, pointing out its deficiencies, showing up the obstacles it puts in the way of positive science. Metaphysics is a branch of philosophy which deals with the nature of reality. As philosophy it accepts no unanalyzed concepts; unlike science it has no postulates taken blindly on faith. The proposition now before us, namely that atoms and their motion are ultimate realities, is bad metaphysics, because it is a blind unanalyzed postulate. How do we know that atoms and their motions are ultimate realities? Why not ask what is reality? Once we are on metaphysical ground, why not take it in real earnest? Why stop on atoms and motions? Atoms themselves are not ultimate simple units, they have shape, size, weight. Now shape, size, weight, what are they after all? They are so many resultants of masses of factual, visual and muscular sensations, which are as little ultimate as are the sensations of color or of pain. It is out of sensations, percepts and ideas that the concept "atom" is framed. Subtract from the atom its sensational, perceptual and ideational elements, abstract from it its shape, size, weight and the ultimate reality of the atoms will become a bare nothing. The atom therefore is ultimately resolved into terms of consciousness. The same holds true in case of motion. Motion is a mental product of what is known as muscular and retinal sensations. What is most ultimately known is only consciousness and its facts. The atom and its motions are after all nothing else but constructs of consciousness. From the standpoint of epistemology, or what the Germans call "Erkenntnisstheorie," we have only a double series of mental phenomena, one standing for the internal and the other for the external world, and not atoms, but mental life may be regarded as the ultimate reality.
From a strictly scientific standpoint, however, we have no right to resolve matter into mind or still less mind into matter, because the two are presented to consciousness as different in kind, even though they both may belong to a general consciousness. Between the two series of facts, the physical and the psychical, there exists a fundamental difference. The door yonder is covered with white paint, the inkstand before me is made of glass, is round, is heavy, is black, but my idea of the door is not covered with white paint, my idea of the inkstand is neither made of glass, nor round, nor heavy, nor black. In short, the facts of consciousness are not spatial.
A fallacy prevalent among the medical profession and now also extant among the populace is the placing of psychic life in the brain. The neurologist, the pathologist ridicule the old Greek belief that the place of the mind is in the heart. Modern science has discovered that the heart is nothing but a hollow muscle, a blood pump at best, the place of mental processes is in the brain. This medical belief now circulating in the popular and semi-scientific literature of today differs but little from the ancient Greek belief, it is just as fallacious and superstitious. It is true that psychic life is a concomitant variable function of nervous processes and brain activity, but neurosis is not the cause of psychosis. The brain does not secrete thought as the liver secretes bile. The mind is not in the brain, nor in fact is the mind anywhere in the universe of space; for psychosis is not at all a physical spatial process.
As fallacious and superstitious is the recent tendency of medical investigation to localize psychic processes, to place different psychic processes in different seats or localities of the brain, thus implying that each psychic process respectively is placed inside some cerebral centre or nerve cells. Psychic life is no doubt the concomitant of nervous brain activity, and certain psychic processes may depend on definite local brain processes, but the given psychic process is not situated in a definite brain center, nor for that matter is it situated anywhere in space.
III The Definition of the Psychic Process
The definition thus far given of psychic life is rather of a negative character. We defined the psychic phenomenon in opposition to the physical phenomenon. Physical phenomena are in space, psychic phenomena are not spatial. Now a negative definition may to many prove rather unsatisfactory. It is, therefore, desirable to define psychic phenomena in more positive terms.
It is now the tendency to define the physical process in social terms and the psychic process in terms of individual cognition. A physical phenomenon is defined as one common to many minds, while a psychic phenomenon is an object of an individual consciousness. I think that such a view of the external physical object, as that which is common to many minds in contrast to the psychic or that belonging to an individual mind only is incorrect from a purely psychological standpoint. Psychologically considered the characteristic trait of a physical object is not that it is common but that it is external. The tree yonder is to me a physical object, not because it is common to many minds, but because I perceive it as external, the sensory elements of the perception carry with them external objectivity.
The social perception of an object may be one of the criteria of external reality, but certainly not the only one, and surely not the chief one. In perceiving an object I do not consider it as a physical object, because I know that it is common to my fellow beings, but because the very psychic process of perception gives the immediate knowledge of externality. An object is considered as physical, not because of its social aspect, but because of its perceived external aspect. Had my perception of the house yonder been a hallucination, I would have still seen it as external and therefore regarded as a physical object; and should this hallucination furthermore be confirmed by the testimony of all my other senses, should I be able to touch it, press against it and feel resistance, knock myself on it and feel concussion and pain, and have a series of tactual and muscular sensations by walking into it and around it, and should I further have this hallucination of all the senses every time I come to this identical spot, the object would be to me an external physical object, and no amount of social contradiction could and would make it different. Regarded from a psychical standpoint an object is considered as physical, not because it is common to other minds, but because it is projected as extensive and external to mind. Not community, but extension, externality is the psychological criterion of the physical object.
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