Aristotle's claim in Metaphysics Z.6 that "each substance is the same as its essence" has long puzzled commentators. For it seems to conflict with two other Aristotelian theses: (1) primary substances are individuals (e.g., Socrates and Callias), and (2) essences are universals (e.g., Man and Horse). Three traditional solutions to this difficulty are considered and rejected. Instead, to make the Z.6 equation consistent with (1) and (2), I propose that it be interpreted to be making something other than a straightforward (...) identity claim. Callias is the same as his essence in the sense that to be identical to Callias is to be the same man as Callias (where Man is the essence of Callias). In general, x is identical to y if, and only if, x and y are the same E (where E specifies the "what it is to be" for x, i.e., the essence of x). So each of Socrates and Callias is the same as his essence, and Man is that essence, but Socrates and Callias are not identical, for they are not the same man. (shrink)