In ‘The Stoics on Conceptions and Concepts’, Katerina Ierodiakonou offers an account of the Stoics’ distinction between ennoiai and ennoēmata (‘conceptions’ and ‘concepts’), and also of the distinctions suggested by the standard Stoic terminology of concepts also mentioned above: notably, prolēpseis (‘preconceptions’), phusikai ennoiai (‘natural conceptions’), and koinai ennoiai (‘common conceptions’). All these terms appear intended to point to general notions that play a central role in the acquisition of human knowledge, but it remains puzzling how exactly the Stoics understood them or why they introduced them into their doctrine in the first place. Ierodiakonou addresses these issues, as well as further questions debated in the secondary literature. These include whether all human beings necessarily possess concepts or just have the ability to possess them, what is the content of conceptions and how it is determined, what is the ontological status of conceptions and concepts, and what are their epistemological functions.

The chapter aims at investigating the way Galen constructs his philosophical theories in dialogue with his predecessors, both by adhering and by opposing to their doctrines. For this purpose, it focuses on a certain part of his epistemology, namely his account of sense perception and, in particular, his theory of vision. I argue that Galen’s perceptual theory starts from material he finds in the Platonic dialogues, but revises it significantly either in order to reply to objections raised by Plato’s opponents or in order to rebut unfortunate, at least to his mind, adaptations of the Platonic inheritance. Indeed, in his attempt to defend Plato’s views on sense perception, Galen does not recoil from borrowing whatever seems to him valuable from rival philosophical schools, and it is this enriched reworking of the Platonic theory that he adopts as his own philosophical stance. To fully reconstruct and comprehend Galen’s method in his general theory of sense perception and in his theory of vision, I draw my evidence from what Galen tells us about these topics in his extant works, and especially in the seventh book of his treatise On the Doctrines of Hippocrates and Plato.

The phenomenon of reflective awareness, i.e., perceiving that we perceive, has often been at the center of Aristotelian scholarship, whereas that of perceptual attention, i.e., focusing on something we perceive, has been much less studied. I examine in parallel the textual evidence for these phenomena and offer a concurrent analysis of them in order to understand better how Aristotle conceives them. I argue that the Aristotelian notion of the common sense lies at the basis of the explanation of perceptual attention as much as of that of reflective awareness. In the former case, the common sense perceives the special or common perceptible that it pays attention to in its own right, whereas in the latter case it perceives the act of perceiving coincidentally along with the respective special or common perceptible. Following Aristotle, the Peripatetics defended the view that the phenomenon of reflective awareness is due to the common sense, but paid no heed to perceptual attention. On the other hand, the Neoplatonic commentators conflated the two phenomena and explained both of them by postulating either a rational character of the senses or an attentive part in the rational soul.