The ambiguous inference: Sanches’ refutation of the self-contradiction objection to global skepticism

Abstract The global skeptic, who claims to not know anything, is often met by the self-contradiction objection, which claims that if they can establish their own position then they must have knowledge of at least that conclusion. I consider a response to this problem from Francisco Sanches, a 16th-century global skeptic. Sanches’ response is unique in that it concedes the charge of self-contradiction, but argues that self-contradiction does not impede an argument for global skepticism. I first establish that Sanches’ response to the objection differs from that of ancient global skeptics. Then I reconstruct Sanches’ argument, using the underdetermination principle to show that a successful argument for global skepticism does not lead to knowledge of any proposition. Finally, I show how such an argument can be useful to a global skeptic nonetheless, arguing that, if accepted, it gives one a reason to suspend judgment on the question of knowledge.