We will take it as established, then, that [moral] excellence or virtue has to do with pleasures and pains; and that the acts which produce it develop it, and also, when differently done, destroy it; and that it manifests itself in the same acts which produced it.

But here we may be asked what we mean by saying that men can become just and temperate only by doing what is just and temperate: surely, it may be said, if their acts are just and temperate, they themselves are already just and temperate, as they are grammarians and musicians if they do what is grammatical and musical.

We may answer, I think, firstly, that this is not quite the case even with the arts. A man may do something grammatical [or write something correctly] by chance, or at the prompting of another person: he will not be grammatical till he not only does something grammatical, but also does it grammatically [or like a grammatical person], i.e. in virtue of his own knowledge of grammar.