On the Possibility of Skeptical Scenarios

Consider this picture of the skeptical dilemma: Descartes sits in his armchair, wondering what the world is like, and worried whether it is as it seems to be. He realizes that there are many ways the world could be — many possible ways for the world to be — that he lacks the resources to choose between. Since all the possibilities he’s considering include his having experiences like the ones he has actually had, experience cannot help choose between them. In this paper I argue that if the purported possibilities in the above picture are supposed to be genuine metaphysical possibilities, this line of skeptical reasoning does not straightforwardly succeed. The above sketch assumes that Descartes can know the metaphysically possible ways the world might be from the armchair.1 That assumption raises questions about modal epistemology — conceivability and possibility, intuitions about possibility — that have received extensive treatment in the philosophy of mind literature. I argue that plausible constraints in modal epistemology show that justification for believing that certain global skeptical scenarios are metaphysically possible rests on some justified beliefs about the external world, and that this would undermine the skeptical argument. While there may still be local skeptical challenges, skeptics cannot appeal to the metaphysical possibility of skeptical scenarios to generate global external world skepticism.