Abstract

This paper examines an ancient debate over the rationality of perception. What leads the Stoics to affirm, and the Epicureans to deny, that to form a sense-impression is an activity of reason? The answer, we argue, lies in a disagreement over what is required for epistemic success. For the Stoics, epistemic success consists in believing the right propositions, and only rational states, in virtue of their predicational structure, put us in touch with propositions. Since they identify some sense-impressions as criteria of truth and thus as the basis for epistemic success, the Stoics maintain that sense-impressions must be rational. The Epicureans agree with the Stoics that sense-impressions function as criteria of truth, and also agree broadly on what it means for a state to be rational, but deny that sense-impressions are rational because (1) they think that epistemic success must be supported by a state that is necessarily error-free and (2) accept that rational states can be false. In reconstructing this debate, we refine the standard interpretation of the fundamental difference between Epicurean and Stoic epistemology and also develop parallels with epistemological debates today. One upshot is a more nuanced appreciation of the merits of Epicurean epistemology vis-à-vis the Stoics.