ARISTOTLE: NICOMACHAEN ETHICS

"Whether, then, it is not by nature that the end appears to each man such as it does appear, but something also depends on him, or the end is natural but because the good man adopts the means voluntarily virtue is voluntary; for in the case of voluntary, vice will also be nonetheless voluntary; for in the case of the bad man there is equally present that which depends on himself in his actions even if not in his end. If, then, as is asserted, the virtues are voluntary (for we are ourselves somehow partly responsible for our states of character, and it is by being persons of a certain kind that we assume the end to be so and so), the vices will also be voluntary; for the same is true of them. "With regard to the virtues in 'general' we have stated their genus in outline , viz. they are means and they are states of character , and that they tend, by their own nature, to the doing of the acts by which they are produced, and that they are in our power and voluntary, and act as the right rule prescribes. But actions and states of character are not voluntary in the same way; for we are masters of our actions from the beginning right to the end, if we know the particular facts, but though we control the beginning of our states of character the gradual progress is not obvious anymore than it is in illnesses; because it was in our power, however, to act in this way or not in this way, therefore the states are voluntary ." P. 974, "Nicomachaen Ethics," THE BASIC WORKS OF ARISTOTLE (1941, 2001)