 Zeno argues that a certain kind of impression—namely a cognitive impression (phantasia katalêptikê)—is the criterion of truth (cf. Shogry 2018). Zeno’s conception of cognition (katalêpsis, literally grasping, apprehension), and the related notion of a cognitive impression, aim to solve an epistemological problem. Belief-formation aims at the truth; there is a norm inherent in the practice of believing that one should only believe truths. It is not transparent to us, however, which of our beliefs, or claims to the effect that such-and-such is true, are successful in their aim and hit the truth. Zeno argues that some impressions are cognitive. A number of Stoic definitions of the cognitive impression, formulated by Zeno and his successors, are transmitted.  Scholars approach them in at least three ways. First, some scholars consider one of the Stoic definitions (SE M 7.247–52) as canonical (Nawar 2014, Shogry 2018). Two, scholars at times examine specific exchanges between Stoics and skeptics in the assumption that some clauses in Stoic definitions respond to skeptic objections (for example, Nawar 2017). Three, scholars have also pointed out that, here as elsewhere, the Stoics offer a multitude of definitions, without privileging one of them as “the” definition; different definitions may speak to different dialectical contexts or theoretical foci (Vogt 2022).