Recent proposals that frame norms of action in terms of knowledge have been challenged by Bayesian decision theorists. Bayesians object that knowledge-based norms conflict with the highly successful and established view that rational action is rooted in degrees of belief. I argue that the knowledge-based and Bayesian pictures are not as incompatible as these objectors have made out. Attending to the mechanisms of practical reasoning exposes space for both knowledge and degrees of belief to play their respective roles.

This paper presents a new argument for a form of contextualism about ‘justified belief’, the argument being based on considerations concerning the nature of belief. It is then argued that this form of contextualism, although it is true, cannot help to answer the threat of scepticism. However, it can explain many other puzzling phenomena: it can give an account of the linguistic mechanisms that determine how the extension of ‘justified belief’ shifts with context; it can help to defuse some puzzles (...) regarding the closure of justified belief under competent deduction; and it can give a plausible account of the role that practical concerns play in the thinking of a rational believer, allowing for a more plausible kind of "intellectualism" about justified belief. (shrink)