What do our impressions say? The Stoic theory of perceptual content and belief formation

Here I propose an interpretation of the ancient Stoic psychological theory on which (i) the concepts that an adult human possesses affect the content of the perceptual impressions (φαντασίαι αἰσθητικαί) she forms, and (ii) the content of such impressions is exhausted by an ‘assertible’ (ἀξίωμα) of suitable complexity. What leads the Stoics to accept (i) and (ii), I argue, is their theory of assent and belief formation, which requires that the perceptual impression communicate information suitable to serve as the content of belief. In arguing for (i), I reject a rival interpretation on which conceptualization occurs subsequently to the formation of a perceptual impression. In arguing for (ii), I deny that perceptual impressions have two kinds of content: one formulated in an assertible, the other sensory, featuring independently of this assertible. I explore the implications of (i) and (ii) for the Stoic theory of emotions, expertise, and rationality, and argue that they shed new light on the workings of impression, assent, and belief.