Functionalism and causal exclusion

Recent work by Jaegwon Kim and others suggest that functionalism leaves mental properties causally inefficacious in some sense. I examine three lines of argument for this conclusion. The first appeals to Occam's Razor; the second appeals to a ban on overdetermination; and the third charges that the kind of response I favor to these arguments forces me to give up 'the homogeneity of mental and physical causation'. I show how each argument fails. While I concede that a positive theory of mental causation is desirable, there is no reason to think that functionalism renders such a theory unattainable.