Aristotle, Nicomachean Ethics
H. Rackham, Ed.

Morose and elderly people rarely make friends, as they are inclined to be surly, and do not take much pleasure in society; good temper and sociability appear to be the chief constituents or causes of friendship. Hence the young make friends quickly, but the old do not, since they do not make friends with people if they do not enjoy their company; and the same applies to persons of a morose temper. It is true that the old or morose may feel goodwill for each other, since they may wish each other well and help each other in case of need; but they cannot properly be called friends, as they do not seek each other's society nor enjoy it, and these are thought to be the chief marks of friendship. [2]

It is not possible to have many friends in the full meaning of the word friendship, any more than it is to be in love with many people at once （love indeed seems to be an excessive state of emotion, such as is naturally felt towards one person only）; and it is not easy for the same person to like a number of people at once, nor indeed perhaps can good men be found in large numbers. [3] Also for perfect friendship you must get to know a man thoroughly, and become intimate with him, which is a very difficult thing to do. But it is possible to like a number of persons for their utility and pleasantness, for useful and pleasant people are plentiful, and the benefits they confer can be enjoyed at once. [4]

Of these two inferior kinds of friendship, the one that more closely resembles true friendship is that based on pleasure, in which the same benefit is conferred by both parties, and they enjoy each other's company, or have common tastes;