This chapter explores the different grounds for accepting the claim that all truths are knowable, the assumption central to the derivation of Fitch’s result. It argues that although there is no compelling argument for holding that all truths are knowable, there are various positions in which this feature of semantic anti-realism fits naturally; rejecting this puts serious tension into a broad range of philosophical outlooks, including theism and physicalism. In the end, the paradox should be felt by everyone, even those who do not accept the knowability claim, because the heart of the paradox is not simply in what is implied by the knowability claim, but in a lost logical distinction between what is actual and what is possible.
Keywords: knowability paradox, truth, scepticism, anti-realism, theism, physicalism