The good man is he for whom, because he is virtuous, the things that are absolutely good are good; it is also plain that his use of these goods must be virtuous and in the absolute sense good.
In a word, acts of any kind produce habits or characters of the same kind. Hence we ought to make sure that our acts are of a certain kind; for the resulting character varies as they vary. It makes no small difference, therefore, whether a man be trained in his youth up in this way or that, but a great difference, or rather all the difference.
Neither by nature, then, nor contrary to nature do the virtues arise in us; rather we are adapted by nature to receive them, and are made perfect by habit.