Book 2: Moral Virtue.
Chapter 4: The conditions of virtuous action as distinct from artistic production.
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.
But, secondly, the virtues are not in this point analogous to the arts. The products of art have their excellence in themselves, and so it is enough if when produced they are of a certain quality; but in the case of the virtues, a man is not said to act justly or temperately [or like a just or temperate man] if what he does merely be of a certain sort—he must also be in a certain state of mind when he does it; i.e., first of all, he must know what he is doing; secondly, he must choose it, and choose it for itself; and, thirdly, his act must be the expression of a formed and stable character. Now, of these conditions, only one, the knowledge, is necessary for the possession of any art; but for the possession of the virtues knowledge is of little or no avail, while the other conditions that result from repeatedly doing what is just and temperate are not a little important, but all-important.
The thing that is done, therefore, is called just or temperate when it is such as the just or temperate man would do; but the man who does it is not just or temperate, unless he also does it in the spirit of the just or the temperate man.
It is right, then, to say that by doing what is just a man becomes just, and temperate by doing what is temperate, while without doing thus he has no chance of ever becoming good.
But most men, instead of doing thus, fly to theories, and fancy that they are philosophizing and that this will make them good, like a sick man who listens attentively to what the doctor says and then disobeys all his orders. This sort of philosophizing will no more produce a healthy habit of mind than this sort of treatment will produce a healthy habit of body.