In his early work, Contra Academicos, Augustine engages with Academic skepticism (to which he attributes the view that “nothing pertaining to philosophy may be known for certain”). The Academics reached this conclusion by accepting the Stoic thesis that a phantasia kataleptike (“cognitive impression”) is necessary for knowledge, but denying that there were any such impressions and therefore no knowledge. In Contra Academicos III, Augustine engages with Academic skepticism by offering various candidates of what he takes to be phantasiai kataleptikai. To the extent that this issue has received any attention, Augustine is generally assumed to have misunderstood the Stoics: whereas the Stoics mainly discussed “cognitive impressions” in relation to a posteriori empirical claims (e.g. “I know that this man is Socrates”), Augustine transforms the notion and applies it primarily to a priori cognitions: he provides mathematical (e.g. “I know that 2+2 = 4”) and logical (e.g. “I know that either p or -p”) cognitions as phantasiai kataleptikai.
Similarly, Augustine is often accused of misunderstanding the Academics; the story goes that the Academics were preoccupied with epoche (the suspension of judgement), whereas Augustine, by ascribing to them the positive thesis “nothing pertaining to philosophy may be known for certain”, has turned them into dogmatists. In this paper, Augustine's interpretation of both the Academics and the Stoics is explored and defended: his understanding of the Academic position is similar to that of Sextus (who clearly did understand the importance of suspension of judgement) and his understanding of the Stoa actually sheds light on a neglected issue in Stoic epistemology: the question of non-sensory phantasiai kataleptikai. Finally, the notion of what “pertains to philosophy” is explored and compared to the Pyrrhonist views presented in Sextus Empiricus. Although Augustine did not read any Pyrrhonist texts, Augustine's (implicit) consideration of what “pertains to philosophy” (a question vital in determining the scope of skepticism) is fruitfully compared with the Pyrrhonist distinctions between 'urbane' and 'rustic' skepticism. Thus, Augustine emerges as a more insightful and penetrative critic of ancient philosophy than is often recognised.