This article offers an overview of the numerous theories about knowledge—the semantic core of the concept of cognition—and of their traces in Joyce's works. Examining how Joyce's writing constantly addresses questions, such as permanence and change, which date back to classical philosophy, O'Rourke problematizes both the possibility of attaining stable knowledge about realities in constant flux and the subject's very status as knower. He shows that Stephen grounds the reliability of knowledge in Aristotle's theory of sensation and develops it through the theory of the soul as "form of forms," a phrase which conveys the soul's powerful cognitive role as receptive of all reality.