Nicomachean Ethics

...finishes it, and diligently describes and designates it. In the second, he considers virtue, and shows how it is acquired, and what it is in its genus and in general. In the third, he teaches concerning the principles of our actions, and wishing to explain each virtue in particular, he begins to define fortitude and temperance. In the fourth, he continues by explaining liberality, magnificence, and the remaining moral virtues in order, with the exception of justice. In the fifth, he defines justice itself, equity, and goodness. In the sixth, he teaches concerning the five habits and intellectual virtues. In the seventh, [he treats] of heroic virtue, of continence, of constancy, then of pleasure and pain, insofar as they are the objects of those dispositions. In the eighth, of friendship and the species of the same. In the ninth, of the conditions and properties of friendship. In the tenth, of pleasure—so that he may find 그hat which is joined to happiness—and then of both forms of happiness; but he considers especially the contemplative, as will be evident in its proper place.

Now this book of morals is reduced to that part of philosophy which they call active, not because such doctrine contains nothing of speculation, but because it is seen to be ordered toward action as toward its further and ultimate end; and in this also do speculative and active sciences differ among themselves: that the speculative are terminated in speculation and contemplation; the active, however, besides speculation, also require action further, and are directed toward it as toward the ultimate end, as we have said. The mode of this doctrine, which the Philosopher employs in this book, is partly resolutive, partly demonstrative—not a priori, but a posteriori—and a demonstration of the fact, because it is a matter that does not arise from necessary principles, as occurs in the demonstrative sciences where the subject matter permits such a mode of teaching. For it is necessary always to accommodate the mode of teaching to the matter and the subject about which such doctrine is concerned...