Here is an excerpt from Materialism by Brown and Ladyman. I’m not quite sure how to parse their solution.


The argument is called the causal exclusion argument. It challenges the intelligibility of mental causation, and it can be expressed like this: if a mental event M supervenes on a physical event P, and P causes a further physical event P* on which a further mental event M* supervenes, serious doubt can be cast on the claim that M causes M*. The account at the physical level of how P causes P*, together with the supervenient relations, is sufficient to account for the occurrence of M*. The M-to-M* doesn’t seem to be a genuine causal relation.
The philosopher Jerry Fodor has expressed a personal response to the problem in no uncertain terms:
 … if it isn’t literally true that my wanting is causally responsible for my reaching, and my itching is causally responsible for my scratching, and my believing is causally responsible for my saying … if none of that is literally true, then practically everything I believe about anything is false and it’s the end of the world.
(Fodor, 1990, p. 156)

Here’s a situation that may clarify what has worried Fodor so much. Imagine you are deciding whether or not to open the window. It seems as though the world has reached a fork in the road – on one possible future path the window stays shut, while on the other possible

seems as if you hold in your hands, in your choice, which path the future will take. However, if the subvenient base of your deliberation stands in a causal role to the subvenient base of your subsequent decision – to open or not to open – then you would seem to lose your central place in the story. What happens – window opened or window kept shut – can be determined without reference to the supervenient story of you and your deliberations….

Later in the chapter:

This chapter concludes with the outline of an account of human choices and decisions intended to save the world. To begin, in addition to the supervenience of mental entities – thoughts, desires, deliberations and so on, there must too be actions. To clarify this idea, imagine a human being’s arm waving. This may be a simple event in the physical world, but it has become an action if it is a waving goodbye. An action is a physical motion of the body linked with an associated mental state.
On this basis, the deliberation about opening the window could have this analysis: you decide you want the window open; put another way, the wish for the window to be open forms in your mind. You then entertain the fantasy of the window being open and you have thoughts about the means to it being opened. Finally, on this basis, the action is undertaken to open the window.
It will not escape attention that this does not undermine the causal exclusion argument. Rather it simply provides a description of what is going on when we have the feeling that we hold the future in our hands. It does suggest that the opening of the window was based on our desire, but the roots of that desire can be traced at a sub-mental level. If the subvenient base of our minds is taken as our physical bodies, including the brain, it may be argued that this physical system ‘wanted’ the window open, and the mental wish expressed this. This perspective may explicate something of the identity theorist’s perspective, even if identity theory must be abandoned.