Book 2: Moral Virtue.
Chapter 1: Moral virtue is acquired by the repetition of the corresponding acts.
Excellence, then, being of these two kinds, intellectual and moral intellectual excellence owes its birth and growth mainly to instruction, and so requires time and experience, while moral excellence is the result of habit or custom (ἔθος), and has accordingly in our language received a name formed by a slight change from ἔθος.
From this it is plain that none of the moral excellences or virtues is implanted in us by nature; for that which is by nature cannot be altered by training. For instance, a stone naturally tends to fall downwards, and you could not train it to rise upwards, though you tried to do so by throwing it up ten thousand times, nor could you train fire to move downwards, nor accustom anything which naturally behaves in one way to behave in any other way.
The virtues, then, come neither by nature nor against nature, but nature gives the capacity for acquiring them, and this is developed by training.
Again, where we do things by nature we get the power first, and put this power forth in act afterwards: as we plainly see in the case of the senses; for it is not by constantly seeing and hearing that we acquire those faculties, but, on the contrary, we had the power first and then used it, instead of acquiring the power by the use. But the virtues we acquire by doing the acts, as is the case with the arts too. We learn an art by doing that which we wish to do when we have learned it; we become builders by building, and harpers by harping. And so by doing just acts we become just, and by doing acts of temperance and courage we become temperate and courageous.
This is attested, too, by what occurs in states; for the legislators make their citizens good by training; i.e. this is the wish of all legislators, and those who do not succeed in this miss their aim, and it is this that distinguishes a good from a bad constitution.
Again, both the moral virtues and the corresponding vices result from and are formed by the same acts; and this is the case with the arts also. It is by harping that good harpers and bad harpers alike are produced: and so with builders and the rest; by building well they will become good builders, and bad builders by building badly. Indeed, if it were not so, they would not want anybody to teach them, but would all be born either good or bad at their trades. And it is just the same with the virtues also. It is by our conduct in our intercourse with other men that we become just or unjust, and by acting in circumstances of danger, and training ourselves to feel fear or confidence, that we become courageous or cowardly. So, too, with our animal appetites and the passion of anger; for by behaving in this way or in that on the occasions with which these passions are concerned, some become temperate and gentle, and others profligate and ill-tempered. In a word, acts of any kind produce habits or characters of the same kind.
Hence we ought to make sure that our acts be of a certain kind; for the resulting character varies as they vary. It makes no small difference, therefore, whether a man be trained from his youth up in this way or in that, but a great difference, or rather all the difference.