 To develop this purported truism, begin with the thought that for S to have an ability to A it is necessary, but not sufficient, that it be possible that S does A. This claim will be contentious for various more specialized sorts of possibility, such as nomic possibility. But if we may help ourselves to the idea of possibility simpliciter (‘metaphysical possibility,’ on at least one reading of that phrase), then this claim appears plausible. (We will survey some historical and contemporary challenges to it below in Section 4.2.) On the other hand it seems implausible that this sort of possibility is a sufficient condition: there are any number of acts that that are metaphysically possible to perform that an agent might nonetheless not be able to perform.