viii.1.1 One might wonder whether it is possible to use each thing both for its natural purpose and otherwise – and this either in itself or, on the other hand, incidentally. For example, an eye; one might use it to see or also otherwise, to mis-see, by displacing it so that one object appears as two. Both of these use it as an eye, because it is an eye, but there is another, incidental use; for instance, if it were possible to sell it or to eat it. viii.1.2 So too for knowledge. One can use it genuinely and also to make a mistake; for instance, when one voluntarily writes incorrectly one uses one’s knowledge as ignorance, as when one twists one’s hand out of place; and dancing girls sometimes use their feet as hands and vice versa.
viii.1.3 If all virtues are forms of knowledge it would also be possible to use justice as injustice and one would then commit injustice by performing unjust acts on the basis of justice, as one can also perform ignorant acts on the basis of knowledge. But if this is impossible, it is obvious that the virtues would not be forms of knowledge. And if it is not possible to be ignorant on the basis of knowledge, but only to make a mistake and to perform the same actions as are done on the basis of ignorance, then certainly one will also not do anything based on justice as though it were based on injustice. But again, if wisdom is knowledge and something that is true, then it too will behave in the same way. It would then be possible to act foolishly on the basis of wisdom and to make the same mistakes as a fool would make. But if the use of each thing as what it is were simple, then in acting that way people would also be acting wisely.