I have advocated a time-slice-centric model of rationality, according to which there are no diachronic requirements of rationality. Podgorski challenges this picture on the grounds that temporally extended mental processes are epistemically important, rationally evaluable, and governed by diachronic requirements. I argue that the particular cases that Podgorski marshals to make his case are unconvincing, but that his general challenge might motivate countenancing rational requirements on processes like reasoning. However, so long as such diachronic requirements are merely derivative of more (...) fundamental synchronic requirements, so that a pattern of reasoning counts as rational or irrational only in so far as it tends to lead one to better satisfy these fundamental synchronic requirements, we can meet Podgorski’s challenge without significantly deviating from a time-slice-centric approach to epistemology. (shrink)