--Heirloom Causality and the Mind Body problem --

John Cottingham in his book The Rationalists (Oxford University Press, 1988) remarks:
When questioned as to how the soul can be effected by the body and vice versa, given that their natures are so completely different, Descartes is reported to have admitted that this was 'very difficult to explain.' (AT V. 163; CB 28). Unfortunately an explanation, in Cartesian terms, seems not just difficult, but impossible. For the Cartesian model of explanation requires that, if X and Y are causally related, then there must be some intelligible link between X and Y; the cause must be 'like' the effect, or the features found in the effect must be present in some form in the cause (see above pp. 81-2). Yet Descartes has to admit that there is no intelligible connection at all between a certain type of movement in the brain (or pineal gland) and a certain type of sensation...'God could have made the nature of man such that this particular motion in the brain indicated something else to the mind.'

So, the problem is that there is an apparently irresolvable conflict between Descartes' heirloom theory of causality and his mind body dualism; which makes it impossible for him to explain mind body interaction. But mind body interaction is as essential to Cartesian dualism as the claim that them mind and the body are different kinds of substances. So Descartes must be able to explain how it occurs, but he can't.

There are a couple of different strategies one might try to deal with this problem. One might, for example, focus on Descartes' theory of causality and try to show that the theory allows for the interaction of entities as different as minds and bodies.

One scholar who has attempted to trace this problem back to its seventeenth century roots and resolve it in this fashion is Eileen O'Neil in "Mind Body Interaction and Metaphysical Consistency: A Defence of Descartes" in the Journal of the History of Philosophy, No. 25, pp. 337-254, April 1987. One might also consult C.D. Broad's The Mind and its Place in Nature, Routledge & Kegan Paul, New York 1951. (See especially pp. 97-103)

Another possible strategy is to try to show that a better theory of mind body dualism would allow for mind body interaction and avoid the difficulties which plague Descartes' account. Emily Michael in her paper: "Early Modern Concepts of Mind: Reflecting Substance versus Thinking Substance" offers a different kind of dualism (one held by Gassendi among others) which she thinks is more satisfactory than Cartesian dualism. Will this alternative kind of dualism escape the difficulties of the Cartesian account?