 There has been substantial recent work on the causal exclusion problem, which, as noted earlier, arises for any non-reductive theory of mental states. (See the entry on Mental Causation, as well as Bennett 2007, and Funkhouser 2007, for further discussion and extensive bibliographies.) But it is worth discussing a related worry about causation that arises exclusively for role-functionalism (and other dispositional theories), namely, the problem of “metaphysically necessitated effects” (Rupert 2006, Bennett 2007). If pain is functionally defined (either by an a priori or an empirical theory) as the state of being in some lower-level state or other that, in certain circumstances causes wincing, then it seems that the generalization that pain causes wincing (in those circumstances) is at best uninformative, since the state in question would not be pain if it didn't. And, on the Humean view of causation as a contingent relation, the causal claim would be false. Davidson (1980b) once responded to a similar argument by noting that even if a mental state M is defined in terms of its production of an action A, it can often be redescribed in other terms P such that 'P caused A' is not a logical truth. But it's unclear whether any such redescriptions are available to role (vs. realizer) functionalists.