All men of science, whatever their views, consistently act as though they believed in the ability of the human intellect, using the method of logic, to make true judgments about the nature of the world. Such is the behaviour even of the Behaviourist. But, according to his own theory, the Behaviourist (like the other disparagers of mind) has no right to behave in this way. If mind is merely an epiphenomenon of matter, if consciousness is completely determined by physical motions, if the intellect is only a machine for securing food and sexual pleasure, then there is absolutely no reason for supposing that any theory produced by this instrument can have universal validity. If Behaviourism, for example, is correct, there is no reason for supposing that the mind can make any kind of valid judgment about the world. But among judgments about the world figures the theory of Behaviourism. Therefore, if Behaviourism is correct, there is no reason for attaching the slightest importance to the opinions, among others, of Behaviourists. In other words, if Behaviourism is correct, it is probable that Behaviourism is incorrect.
All who advance theories of mind containing the words ‘nothing but,’ tend to involve themselves in this kind of contradiction. The very fact that they formulate theories which they believe to have general validity, the very fact that, having studied a few phenomena (which are anyhow not phenomena but ‘epiphenomena,’ facts of consciousness) they should feel themselves justified in making inductions about all phenomena past, present and future, constitutes in itself a sufficient denial of the validity of ‘nothing-but’ judgments concerning the nature of the mind. All science is based upon an act of faith—faith in the validity of the mind’s logical processes, faith in the ultimate explicability of the world, faith that the laws of thought are laws of things. In practice, I repeat, if not always in theory, such conceptions are fundamental to all scientific activity. For the rest, scientists are opportunists. They will pass from a common-sense view of the world to advanced idealist theories, making use of one or the other according to the field of study in which they are at work. Unfortunately, few scientists in these days of specialization are ever called upon to work in more than one small field of study. Hence there is a tendency on the part of individual specialists to accept as true particular theories which are in fact only temporarily convenient. It is highly unfortunate that so few scientists are ever taught anything about the metaphysical foundations of science.
Recent research in medicine, in experimental psychology and in what is still called parapsychology has thrown some light on the nature of mind and its position in the world. During the last forty years the conviction has steadily grown among medical men that very many cases of disease, organic as well as functional, are directly caused by mental states. The body becomes ill because the mind controlling it either secretly wants to make it ill, or else because it is in such a state of agitation that it cannot prevent the body from sickening. Whatever its physical nature, resistance to disease is unquestionably correlated with the psychological condition of the patient.[23] That even so grossly ‘physical’ a complaint as dental caries may be due to mental causes was maintained in a paper read before the American Dental Congress in 1937. The author pointed out that children living on a perfectly satisfactory diet may still suffer from dental decay. In such cases, investigation generally shows that the child’s life at home or at school is in some way unsatisfactory. The teeth decay because their owner is under mental strain.
Mind not only makes sick, it also cures. An optimistic patient has more chance of getting well than a patient who is worried and unhappy. The recorded instances of faith-healing include cases in which even organic diseases were cured almost instantaneously.
Experimenters in hypnotism have shown that it is possible to raise a blister by merely telling a deeply hypnotized subject that he is being burnt. The metal which touches the skin is cold; but the subject feels pain and displays all the physical symptoms of a burn. Conversely, hypnotism can be used to produce anaesthesia, even in major operations. Thus, in the late forties of last century, James Esdaile performed over two hundred operations upon patients anaesthetized by means of hypnosis. Esdaile’s surgical technique was pre-Listerian; nevertheless, the mortality among his hypnotized patients was extremely low.
Systematic researches designed to demonstrate the existence of telepathy have been conducted at intervals during the last fifty years. Of these the most recent and the most considerable are those which Professor Rhine has been carrying out at Duke University in North Carolina. Rhine’s work, which has been successfully repeated by several other investigators, leaves no doubt as to the existence of telepathy and clairvoyance and very little doubt as to the existence of pre-vision. In his presidential address delivered before the Society for Psychical Research in 1936, Professor C. D. Broad discusses the problems raised by telepathy. How does telepathy work? That it is not a physical process akin to radio transmission is obvious; for the strength of the messages does not diminish with distance. After discussing various other alternatives, Professor Broad concludes that it is probably necessary to postulate the existence of some kind of purely mental medium, in which individual minds are bathed, as in a kind of non-physical ether. If there is such a thing as pre-vision, we must presume that this mental medium has its existence outside time. It would seem, then, that mind, or at any rate something of a mental nature—a ‘psychic factor’ within a psychic medium—exists independently of the body and off the spatial and temporal conditions of bodily life.
I have considered the scientific picture of the material world and the scientific pictures of mind. It is now time to consider the scientific picture of the history of this mental-material conglomerate. The only part of the universe with which we have direct acquaintance is this planet. It is also the only part of the universe in which we can study life and consciousness. How far are we justified in drawing inferences about the general nature of things from the inferences previously drawn from the rather scanty evidence about the history of life on this planet? It is hard indeed to say. We have seen that matter on the earth seems to be built up from the same energy-units as constitute matter in remote parts of the universe and that the laws of thought are laws of things, not only here, but, to all appearance, also there. This being so, to generalize from our inferences regarding the nature of our planetary history would seem to be a process that is at any rate not completely illegitimate. Meanwhile, however, we have to discover what the nature of that history is.
I am not qualified to discuss the methods of evolution, nor, in the present context, does there seem to be any good reason for embarking upon such a discussion. For our particular purposes, the results of evolution are more significant than the mechanism by which those results were achieved. In regard to this mechanism, the evidence available seems to point to the conclusion that mutation, hybridization, retardation of growth and fœtalization (which are themselves the products of mutation), and natural selection are sufficient to account for evolutionary change and that it is unnecessary to invoke such concepts as orthogenesis or the inheritance of acquired characters.
Lamarckism has often been supported by those who are anxious to vindicate the pre-eminence of mind in the world. But, as Haldane has pointed out, these crusaders are really doing a disservice to their cause. If characters acquired as the result of more or less intelligently directed effort are inherited, then we should expect evolution to be a rapid process. But in fact it is extremely slow. If evolution is due to ‘cunning’ rather than ‘luck,’ then the cunning must be of a pretty feeble kind; for it has brought life a relatively short way in a very long time. In feet, the evidence for Lamarckism is extremely inadequate. (Neither Lamarckism nor the orthogenetics theory seems to be compatible with the fact that most mutations are demonstrably deleterious.) Mind, as we know, can affect the body profoundly and in a great variety of ways. But, as a matter of empirical fact, this power of affecting the body is limited. To modify the arrangement of the genes must be numbered, it would seem, among the things it cannot do.
There is only one other point in regard to the mechanism of selection about which I need speak in the present context. Competition, when it exists, is of two kinds: between members of different species (inter-specific) and between members of the
