Abstract

On the face of it, in ordinary practices of rational assessment, we criticize agents both for the combinations of attitudes, like belief, desire, and intention, that they possess at particular times, and for the ways that they behave cognitively over time, by forming, reconsidering, and updating those attitudes. Accordingly, philosophers have proposed norms of rationality that are synchronic—concerned fundamentally with our individual time-slices, and diachronic—concerned with our temporally extended behaviour. However, a recent movement in epistemology has cast doubt on the very existence of requirements of the latter type. My aim in this paper is to address what I take to be the most direct and general recent attack on diachronic epistemic rationality, the arguments for so-called ‘time-slice epistemology’ by Brian Hedden. I argue that Hedden's attempt to motivate the rejection of diachronic rational norms ultimately fails, and in particular that an independently attractive view about the nature of such norms, namely one on which such norms govern processes, escapes his assault unscathed.