A nonreductionist's solution to Kim's explanatory exclusion problem

In numerous papers Jaegwon Kim argues that nonreductive materialists (i.e., those philosophers who believe that there are no irreducible non-physical objects in the universe, and yet there are irreducible psychological properties which are indispensable in intentional psychological explanations) face two problems. One is that intentional mental properties are not causally relevant; the other is that explanations appealing to these properties are excluded by explanations appealing to physical, in particular, microphysical, properties.1 The first problem can be called the problem of epiphenomenalism. The second problem is what Kim calls the problem of explanatory/causal exclusion. Epiphenomenalism is not just a problem for nonreductive materialists, but a problem for psychology (as a science of psychological explanation), and for anyone who believes that our thought is the cause of our action. Kim argues that the exclusion problem, on the other hand, is especially a problem for nonreductive materialists. Nonreductive materialists typically buy into the principle of the causal closure of the physical domain, according to which "any physical event that has a cause at time t has a physical cause at t..... [I]f we trace the causal ancestry of a physical event, we need never go outside the physical domain." [Kim 1989b, p. 280] One cannot reject this principle unless one is willing to go back to Cartesian dualism. But the problem is, if all causation is done at the physical level, then there is no causal work left for mental kinds. If mental kinds do not play any causal role, then intentional psychological explanations that appeal to mental properties are not warranted. Therefore, Kim concludes, nonreductive materialism is an untenable position. Some nonreductionists (Davidson, Dretske, LePore & Loewer, Jackson & Pettit, for example) have tried to argue for the causal relevancy of mental properties from an..