Aristotle, Eudemian Ethics

[1246b] [1] And also if it is not possible from knowledge to be ignorant, but only to make mistakes and do the same things as one does from ignorance, a man will assuredly never act from justice in the same way as he will act from injustice. But since wisdom is knowledge and a form of truth, wisdom also will produce the same effect as knowledge, that is, it would be possible from wisdom to act unwisely and to make the same mistakes as the unwise man does; but if the use of anything qua itself were single,¹ when so acting men would be acting wisely. In the case of the other forms of knowledge, therefore, another higher form causes their diversion; but what knowledge causes the diversion of the actually highest of all? Obviously there is no longer any knowledge or any mind to do it. But moreover goodness does not cause it either; for wisdom makes use of goodness, since the goodness of the ruling part uses that of the ruled. Who then is there in whom this occurs? or is it in the same way as the vice of the irrational part of the spirit is termed lack of control, and the uncontrolled man is in a manner profligate—possessing reason, but ultimately if his appetite is powerful it will turn him round, and he will draw the opposite inference? Or is it manifest that also if there is goodness in the irrational part but folly in the reason, goodness and folly are transformed in another way? so that it will be possible to use justice unjustly and badly, and wisdom unwisely; and therefore the opposite uses also will be possible. [20] For it is strange if whereas when wickedness at any time arises in the irrational part it will pervert the goodness in the rational and cause it to be ignorant, yet goodness in the irrational part when there is folly in the rational should not convert the folly and make it form wise and proper judgements, and again wisdom in the rational part should not make profligacy in the irrational act temperately—which seems to be what self-control essentially is. So that there will actually be wise action arising from folly. But these consequences are absurd, especially that of using wisdom wisely as a result of folly; for that is a thing which we certainly do not see in other cases—for instance profligacy perverts one's medical knowledge or scholarship, but it does not pervert one's ignorance if it be opposed to it, because it does not contain superiority, but rather it is goodness in general that stands in this relation to badness; for example, the just man is capable of all that the unjust man is, and in general inability is contained in ability. So that it is clear that men are wise and good simultaneously, and that the states of character above described belong to a different person, and the Socratic dictum 'Nothing is mightier than wisdom,' is right. But in that by 'wisdom' he meant 'knowledge,' he was wrong; for wisdom is a form of goodness, and is not scientific knowledge but another kind of cognition.

But wisdom is not the only thing which acting in accordance with goodness causes welfare,