Interaction and Physiology

Abstract

In Body and Mind (Garden City, N.Y., I970) Keith Campbell argues that there is no dualist interaction between the mental and the physical. Given recent advances in brain physiology, he says, it is very likely that 'for explaining events in the brain, physiology is, in principle, complete' (P. 52). The completeness of physiology is, however, 'incompatible with matter-spirit interaction' (p. 40). Thus it is very likely that dualist interactionism is false. In this paper I hope to show that Campbell's argument does not succeed. Campbell construes the completeness of physiology in at least three different ways. At times he envisages the possibility of explaining (and thus predicting and retrodicting) every brain happening using purely physical laws, i.e. laws referring only to physical states or events. Thus, given a complete physiology, every brain event would 'follow recognized physical laws' (p. 5I), and no brain event would involve a 'departure from physical law' (p. i8). But if every brain event can be explained using purely physical laws, interactionism is, he claims, false: 'If the brain's activities of a physical kind all occur in accordance with physical laws, suffering a burn, tasting the sweetness of sugar, or smelling the piquancy of cloves are processes in which experience of the quality in question is inoperative in behaviour' (p. i iI). IEven if it should prove possible to provide purely physical explanations of every brain event, however, it does not follow, as Campbell claims, that interactionism is false. Suppose a purely physical law correlating successive brain states of kinds B1 and B2, and having the form: B1 if, and only if, B2. Suppose, too, a psychophysical law correlating the simultaneous occurrence of mental states of kind M1 and brain states of kind B1, and having the form: M1 if, and only if, B1. For example, suppose that pain of a certain kind (M1) occurs if, and only if, the brain is simultaneously in a certain physical state (B1), and the brain is in that state if, and only if, it is subsequently in another particular kind of physical state (B2). Now in the situation supposed one can explain the occurrence of a B2 using only the purely physical law B1 if, and only if, B2. But one can also explain the occurrence of a B2 using the psychophysical law M1 if, and only if, B2. One can explain the subsequent brain state by referring either to the prior brain state or to the prior pain (or to both, for that matter). Purely physical explanations are not, then, incompatible with psychophysical ones. It follows that the possibility of a complete physiology, in the present sense, does not rule out interactionist explanations of events in the brain. This is not, of course, to say that psychophysical explanations must be interactionist, for epiphenomenalism is a possibility here. More of this later.