"The perfect friendship is that of virtuous people, and who resemble each other in their virtue; for these wish each other well, inasmuch as they are good; and I add that they are good in themselves. Those who wish their friends well from such a noble motive are the friends _par excellence_. Hence it is that the friendship of such generous hearts lasts as long as they remain good and virtuous themselves; now virtue is a substantial and durable thing. Each of the two friends is in the first place good in himself, and he is, moreover, good to all his friends, for good people are useful to each other, and also mutually agreeable to each other. Such a friendship unites, then, all the conditions. There is nothing more lovely. It is quite natural, however, that such friendships are very rare, because there are very few people of such a disposition. It requires, moreover, time and habit. The proverb is true which says that people can hardly know each other well, 'before having eaten together bushels of salt.' In the same way persons cannot be friends before having shown themselves worthy of affection, before reciprocal confidence is established." (Nicomachean Ethics, liv. viii., ch. vii.) Friendship, according to Aristotle, consists in _loving_ rather than in _being loved_. "Friendship, besides, consists much rather in loving than in being loved. The proof of it is the pleasure mothers experience in lavishing their love.... To love is, then, the great virtue of friends; it is thus that the most unequal of people may be friends; their mutual esteem renders them equals." (Ch. viii.) Friendship gives rise to a number of delicate problems: they may be found discussed in great detail in Cicero's _Treatise on Friendship_. =65. Kant's precepts touching friendship.=--Among the moderns, Kant is the only moral philosopher who has given friendship a place in practical morality. He has found new and delicate traits to add to the rules of the ancients. He insists above all on what he calls "the difficulties of friendship," and above all on the difficulty of conciliating "love and respect." "To look at the moral aspect of the thing," he says, "it is certainly a duty to call a friend's attention to the mistakes he may commit; for it is done for his good, and is consequently a duty of love. But the friend, thus admonished, sees in the thing but a lack of esteem he had not expected, and thinks he has lost something in your mind; or, seeing himself thus observed and criticised, may at least be in constant fear of losing your esteem. Besides, the fact alone of being observed and censured, will already appear to him an offensive thing in itself.