Problematisation about concepts and related notions in Aristotle greatly depends on the particular work or works under consideration. Richard McKirahan’s contribution ‘Concepts and Concept Formation in Aristotle’s Logical Works’ argues that an account of how concepts are formed may be extracted from passages of the Organon, on topics relating to the problem of how we gain knowledge of scientific principles, in combination with Aristotle’s statements on the relations among objects in the world, affections in the soul, and language. Aristotle’s view is pieced together on the basis of the account in Posterior Analytics 2.19, supplemented by the parallel account in Metaph. A.1, as well as Aristotle’s remarks on the utility of dialectic for the sciences in Top. 1.2 and the brief discussions of epagōgē (frequently and controversially rendered by ‘induction’: An. Post. 1.18 and 1.31). The chapter also addresses questions about the nature of perception as conceived in the Organon, the epistemic status of experience, the transition from the awareness of individuals to the grasp of universals, the status of nous, and the relation between universals and concepts.

Much of our little information on Zeno's life comes from the prologue of Plato's Parmenides. Most scholars accept Plato's statement that when Socrates was “very young” (though old enough to engage in philosophical debate) Zeno was forty and Parmenides was sixty-five (Parm. 127a-b). The setting of the Parmenides is the quadrennial Great Athenaia, and the best guesses for its dramatic date are 454 B.C. when Socrates was 15 and 450 B.C. when he was 19. Also, Plato's statement that “Zeno was of a good height and handsome to see; the story goes that he had been Parmenides' young lover” (127b) is perfectly possible, though not otherwise attested. Even if the setting of the Parmenides is historically plausible, the notorious unreliability of Plato's reports on earlier philosophers makes it unwise to take much else of what he says on trust. The conversation in the Parmenides certainly did not take place, and we may fairly doubt that Socrates met the philosophers from Elea. Further, Plato indicates that Zeno's treatise was unknown in Athens prior to the dramatic date of the Parmenides (127c), but he also implies that it was written many years earlier, and he says it had been circulated (apparently soon after its writing) without Zeno's authorization (I28d) – claims that although not actually contradictory are hard to reconcile.