The Eighth and Ninth Books contain the treatise on Friendship.
The subject deserves a place in an Ethical treatise, because of its connexion with virtue and with happiness. Several questions have been debated concerning Friendship,--Is it based on likeness or unlikeness? Can bad men be friends? Is there but one species of Friendship, or more than one? (I.) Some progress towards a solution of these questions may be made by considering what are the objects of liking; these are the good, the pleasant, the useful. By the good is not meant the absolute good of Plato, but the apparent good. Inanimate things must be excluded, as wanting reciprocation (II.). The varieties of friendship follow these three modes of the likeable. The friendships for the useful and the pleasant, are not disinterested, but self-seeking; they are therefore accidental and transitory; they do not involve intimate and frequent association. Friendship for the good, and between the virtuous, is alone perfect; it is formed slowly, and has the requisites of permanence. It occurs rarely (III.). As regards the useful and the pleasant, the bad may be friends. It may happen that two persons are mutually pleasant to each other, as lover and beloved; while this lasts, there is friendship. It is only as respects the good, that there exists a permanent liking for the person. Such friendship is of an absolute nature; the others are accidental (IV.). Friendship is in full exercise only during actual intercourse; it may exist potentially at a distance; but in long absence, there is danger of its being dissolved. Friendship is a settled state or habit, while fondness is a mere passion, which does not imply our wishing to do good to the object of it, as friendship does (V.). The perfect kind of friendship, from its intensity, cannot be exercised towards more than a small number. In regard to the useful and the pleasant, on the other hand, there may be friendship with many; as the friendship towards tradesmen and between the young. The happy desire pleasant friends. Men in power have two classes of friends; one for the useful, the other for the pleasant. Both qualities are found in the good man; but he will not be the friend of a superior, unless he be surpassed (by that superior) in virtue also. In all the kinds of friendship now specified there is equality (VI.). There are friendships where one party is superior, as father and son, older and younger, husband and wife, governor and governed. In such cases there should be a proportionably greater love on the part of the inferior. When the love on each side is proportioned to the merit of the party beloved, then we have a certain species of equality, which is an ingredient in friendship. But equality in matters of friendship, is not quite the same as equality in matters of justice. In matters of justice, equality proportioned to merit stands first--equality between man and man (no account being taken of comparative merit) stands only second. In friendship, the case is the reverse; the perfection of friendship is equal love between the friends towards each other; to have greater love on one side, by reason of and proportioned to superior merit, is friendship only of the second grade. This will be evident if we reflect that extreme inequality renders friendship impossible--as between private men and kings or gods. Hence the friend can scarcely wish for his friend the maximum of good, to become a god; such extreme elevation would terminate the friendship. Nor will he wish his friend to possess all the good; for every one wishes most for good to self (VII.). The essence of friendship is to love rather than to be loved, as seen in mothers; but the generality of persons desire rather to be loved, which is akin to being honoured (although honour is partly sought as a sign of future favours). By means of love, as already said, unequal friendships may be equalized. Friendship with the good, is based on equality and similarity, neither party ever desiring base services. Friendships for the useful are based on the contrariety of fulness and defect, as poor and rich, ignorant and knowing (VIII.). Friendship is an incident of political society; men associating together for common ends, become friends. Political justice becomes more binding when men are related by friendship. The state itself is a community for the sake of advantage; the expedient to all is the just. In the large society of the state, there are many inferior societies for business, and for pleasure: friendship starts up in all (IX.).