- Mechanistic brain science proceeds on the working assumption that every bodily event has a physical cause in the prior state of the central nervous system. Traditional moral and religious thought, on the other hand, has always presupposed that some at least of our behaviour is determined by our thinking and deciding. This apparent conflict has given rise to suggestions that unless some parts of our nervous system are found to be open to non-physical influences, brain science will effectively debunk all talk of man as a spiritual being, and oblige us to accept a purely materialistic view of our nature. Many people seem to expect a battle to be fought between religion and the neurosciences like that waged by some theologians in the nineteenth century against evolutionary biology.
- How justified is this impression? It is true that the seventeenth-century French philosopher-mathematician Rene Descartes held that the mind or soul would be powerless to influence bodily action unless some part of the brain could act as a transmitter-receiver for its controlling signals. He considered that the pineal gland, in the middle of the head, was ideally suited to the purpose. "In man," he says,
the brain is also acted on by the soul which has some power to change cerebral impressions just as those impressions in their turn have the power to arouse thoughts which do not depend on the will. . . . Only [figures of excitation] traced in spirits on the surface of [the pineal] gland, where the seat of imagination and common sense [the coming together of the senses] is . . . should be taken to be . . . the forms or images that the rational soul will consider directly when, being united to this machine, it will imagine or will sense any object. In recent years the neurophysiologist Sir John Eccles and the philosopher Sir Karl Popper have advanced theories of the "interaction" of mind and brain, which, though they differ in important respects from that of Descartes, agree with him that the brain must be open to non-physical influences if mental activity is to be effective.
- At first sight this might indeed seem obvious common sense; but a simple counter-example throws some doubt on the logic of the argument. We are nowadays accustomed to the idea that a computer can be set up to solve a mathematical equation. The mathematician means by this that the behaviour of the computer is determined by the equation he wants to solve; were it not so, it would be of no interest to him. On the other hand, if we were to ask a computer engineer to explain what is happening in the computer, he could easily demonstrate that every physical event in it was fully determined (same word) by the laws of physics as applied to the physical components. Any appearance of conflict here would be quite illusory. There is no need for a computer to be "open to non-physical influences" in order that its behaviour may be determined by a (non-physical) equation as well as by the laws of physics. The two "claims to determination" here are not mutually exclusive; rather they are complementary.
- The analogy is of course a limited one. We (unlike our computing machines) are conscious agents. The data of our conscious experience have first priority among the facts about our world, since it is only through our conscious experience that we learn about anything else. Our consciousness is thus not a matter of convention (like the mathematical significance of the computer's activity) but a matter of fact which we would be lying to deny. Nevertheless the logical point still holds. If we think of our mental activity as "embodied" in our brain activity, in the sense in which the solving of an equation can be embodied in the workings of a computer, then there is a clear parallel sense in which our behaviour can be determined by that mental activity, regardless of the extent to which our brain activity is determined by physical laws. The two explanations, in mental and in physical terms, are not rivals but complementary.
- Note that we are here thinking of mental activity as embodied in brain activity rather than identical with brain activity. The latter is a notion favoured by what is called "materialist monism," at the opposite extreme from the "interactionism" of Eccles and Popper. This would simply identify "mind" and "brain," and would go so far as to attribute "thinking" and other mental activities to the matter of which the brain is composed. The objection to this extreme view can be understood by once again considering the example of a computer. It is true that the solving of an equation is not a separate series of events, running in parallel with the physical happenings in the machine. It is rather the mathematical significance of one and the same series of events, whose physical aspect is well explained by the engineer. On the other hand it would be nonsensical on these grounds to identify equations with computers as physical objects, or to attribute mathematical properties (such as "convergence" or "being quadratic") to the physical matter in which the equation is embodied.
- By the same token, even if we regard our thinking and deciding as a "mental" or "inner" aspect of one and the same (mysterious) activity that the neuroscientist can study from the outside as brain activity, this gives no rational grounds for taking the material aspect as more "real" than the mental, still less for identifying the two and speaking of thinking and deciding as attributes of matter. This would be a confusion of categories belonging to different logical levels, for which nothing in brain science offers any justification.
- It might appear that thinking of our conscious experience as "embodied" in our brains would still be incompatible with the Christian concept of "life after death1." What we have seen in the case of the computer, however, shows that there need be no conflict. The physical destruction of a computer is certainly the end of that particular embodiment of the equation it was solving. But it leaves entirely open the possibility that the same equation could be re-embodied, perhaps in a quite different medium, if the mathematician so desires. By the same logic, mechanistic brain science would seem to raise equally little objection to the hope of eternal life expressed in biblical Christian doctrine, with its characteristic emphasis on the "resurrection" (not to be confused with resuscitation) of the body. The destruction of our present embodiment sets no logical barrier to our being re-embodied, perhaps in a quite different medium, if our Creator so wishes.
Originally in "Gregory (Richard), Ed. - Oxford Companion to the Mind".
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