In a series of papers and a recent book, Fred Dretske has been working out an innovative account of how reasons explain behavior. His starting point is what we may call “the causal thesis”, often associated with Davidson, that reasons rationalize behavior by being its cause. With Davidson, therefore, Dretske takes rationalizing explanations to be a species of causal explanation, explanations that specify the causal antecedents of their explananda. Reasons are beliefs, desires, and other assorted “contentbearing” states, and these are among the paradigmatic instances of intentional mental states. Thus, the problem of explaining how reasons rationalize (that is, explain by providing reasons) is, for Dretske, the problem of giving an account of how intentional states can be causes, that is, the problem of intentional or rational causation. If we further assume, with Dretske, that the behavior to be rationalized is, or often involves, bodily events and processes, our problem is seen as a special case of the problem of psychophysical causation, that of understanding how mental events or states can enter into causal relations with physical events, as their causes or their effects. There is of course an even broader problem of mental causation, the problem of explaining how mental events can enter into any sort of causal relation, either as causes or as effects, whether with physical events or with other mental events.

The reality of the mental is closely tied to the possibility of mental causation, and anyone who takes a realist attitude toward the mental must be prepared with an account of how mental causation is possible.