Conceivability and the A Priori

Abstract

David Chalmers claims that there is (i) a sense of “conceivable” in which conceivability directly implies metaphysical possibility and (ii) a sense in which it implies epistemic possibility. We have reason to doubt this thesis. First, the proposed ambiguity cannot account for some basic examples; even in the context of a natural reading of the famous zombie argument none of the two senses really seem to be appropriate. Second, a proper analysis of conceivability does not validate the claim that conceivability always implies some kind of possibility. “It is conceivable that S” is not ambiguous and merely implies that it is epistemically possible that S is not inconsistent. Finally I show how to square the weakness of these implications with the fact that thought experiments sometimes inform us of what we should rationally believe to be possible.