Abstract

Aristotle and Eudemus report a Speusippean argument to the effect that defining anything requires knowing everything. Scholars have failed to make sense of this argument. This paper argues that the main preoccupations to which the Puzzle is meant to respond are: (i) to ensure the co-extensiveness of the definition with the definiendum; (ii) to rule out a particular definitional mistake—underdivision. The implications of the Puzzle for Speusippus’ conception of knowledge are further explored.