Several of the most compelling anti-materialist arguments are motivated by the supposed existence of an unbridgeable epistemic gap between first-person subjective knowledge about one’s own conscious experience and third-personally acquired knowledge. The two with which this paper is concerned are Frank Jackson’s ‘knowledge argument’ and David Chalmers’s ‘modal argument’. The knowledge argument and the modal argument are often taken to function as ‘two sides of the same coin … in principle each succeeds on its own, but in practice they work (...) best in tandem’. This paper disagrees with the above claim, and argues that when considered together the knowledge argument and modal arguments illuminate each other’s weaknesses. These weaknesses become apparent when we acknowledge the epistemic richness of the cognitive aspect of perceptual experience, and question the epistemic role that any non-cognitive aspect might play. Closer examination of judgments about what it’s like to have a perceptual experience reveals fundamental problems with the knowledge argument, and when these problems are exposed, the two arguments can no longer ‘buttress each other where help is needed’. It becomes clear that neither is likely to succeed on its own, and when taken together both are destabilized. (shrink)