This chapter offers a survey of the views on concepts held by Greek philosophers from ca. 250 CE to 550 CE. The first section explores how late antique accounts of ordinary concepts are based on the Stoic view of common notions (koinai ennoiai) and how, for Neoplatonists, common notions are connected with Platonist recollection. The second section focuses on abstract concepts and universals. It is argued that Porphyry conceives of abstraction and universals along Peripatetic lines. Porphyry, however, supplements abstraction with Platonic innatism: the relation between abstractionism and innatism is problematic both for Porphyry and for later authors such as Hermias of Alexandria. The third section explores Plotinus’s view of innate concepts and recollection. These issues raise the question of how experience and innatism interact in Plotinus’s account of concept acquisition. The fourth section explores late Neoplatonist views of innate concepts as psychic forms, or logoi.

Epistemology is in many ways important for Spinoza’s philosophy. It underlies his metaphysics, as well as his ethics and his political theory, and it also connected in many interesting ways with his psychological views on the mental life of human subjects. It is against this background that the present chapter discusses several key concepts and doctrines that Spinoza establishes in his epistemology, such as his views on truth and adequacy, the definition of idea and the denial of the notion of innate ideas, the famous distinction of the three kinds or rather “genera” of knowledge, the cognitive psychology underlying the discussion of the process of the imagination, humanity’s capacity for rationality, and finally the idea of our being blessed by intuitive knowledge. Moreover, regarding Spinoza’s denial of skepticism as the basic motivation driving his epistemology, the chapter also shows how his epistemological views develop over time. Altogether, it is argued that Spinoza manages to establish an epistemology that is both quite consistent on its own terms and successful in providing a stable foundation for his metaphysical, ethical and political views.