  You might ask why any of these relations should secure the desired solution. One thought is that if mental properties are immanent in their physical realizers, the causal powers of a mental property are included among those of its realizer. Consider again mental property M and one of its realizers in a given instance, P. Plausibly, M’s powers are included in P’s. Both properties, for example, have the power to cause a certain kind of behavior, but because of its greater “specificity”, P has in addition to this powers that M lacks. Now in general we don’t think that wholes causally compete with, or are excluded by, their parts. When Gus steps on Lilian’s toe, his foot’s causing Lilian discomfort doesn’t exclude Gus’s causing her discomfort. Both Gus and his foot coexist as causes, without competition and, we might add, without overdetermination. A similar point could be made about properties: if the causal powers of M are included in those bestowed by P, then P’s causal relevance to behavior, far from excluding M’s, includes it. (Approaches along these lines have been developed in Antony 1999; Shoemaker 2001; Wilson 1999, 2011; Clapp 2001; critical discussions include Heil 1999, 2011; McLaughlin 2007; Kim 2010; Ney 2010; Audi 2012.)