Aristotle, Nicomachean Ethics
H. Rackham, Ed.

the association of the sexes aims only at continuing the species, human beings cohabit not only for the sake of begetting children but also to provide the needs of life; for with the human race division of labor begins at the outset, and man and woman have different functions; thus they supply each other's wants, putting their special capacities into the common stock. Hence the friendship of man and wife seems to be one of utility and pleasure combined. But it may also be based on virtue, if the partners be of high moral character; for either sex has its special virtue, and this may be the ground of attraction. Children, too, seem to be a bond of union, and therefore childless marriages are more easily dissolved; for children are a good possessed by both parents in common, and common property holds people together. [8]

The question what rules of conduct should govern the relations between husband and wife, and generally between friend and friend, seems to be ultimately a question of justice. There are different claims of justice between friends and strangers, between members of a comradeship and schoolfellows. 13.

There are then, as we said at the outset, three kinds of friendship, and in each kind there are both friends who are on an equal footing and friends on a footing of disparity; for two equally good men may be friends, or one better man and one worse;