In this paper I shall examine the notion of ταὐτόν - commonly translated as 'same' or 'identical' - and its relevance to so-called essential predications, as effected through the use of ὅπερ in Aristotle. It will be shown that propositions of the type 'A is ὅπερ B' involve an essential predication where either a genus is affirmed of a species, or a species of an individual. The possibility of such predications will be founded upon the doctrine of the categories and the ontological distinction between essence and accident. Besides predications involving generic or specific identity, others effected through propositions of the type 'A is ὅπερ B' will be seen to be employed by Aristotle. These latter predications will be stricto sensu neither essential nor accidental, yet will involve a necessary connection between subject and predicate. I shall then examine why Aristotle believes there to be a necessary application of predicate to subject in these cases, as well as why certain problems of identity and synonymy follow therefrom.
Urbanas, Alban, "On 'Essentially' (hoper) in Aristotle" (1985). The Society for Ancient Greek Philosophy Newsletter. 140.