In this paper, I propose a principle of doxastic rationality based on Bernard Williams's argument against doxastic voluntarism. This principle, I go on to show, undermines a number of notions of epistemic duty which have been put forth within the framework of virtue theory. I then suggest an alternative formulation which remains within the bounds of rationality allowed for by my principle. In the end, I suggest that the failure of the earlier formulations and the adoption of the latter tend (...) to vindicate the initial grounding of virtue epistemology in reliabilist intuitions. (edited). (shrink)