[古希臘]亞裏士多德/Aristotle
The ancients listed friendship among the highest of virtues. It was an essential element in the happy or fully flourishing life.“For without friends,”Aristotle says,“no one would choose to live, though he had all other goods.”Words worth remembering in a world of perishable“goods.”
According to Aristotle, friendship either is, or it involves, a state of character, a virtue. There are three kinds of friendship. These are based on pleasure in another's company（friendship of pleasure），or on usefulness in association（friendships of utility），or on mutual admiration（friendships in virtue）.All are essential to the good life, and the best sorts of friends will not only admire each other's excellence, but take pleasure in each other's company and find their association of mutual advantage. Here is a portion of Aristotle's classic discussion.
As the motives to Friendship differ in kind, so do the respective feelings and Friendships. The species then of Friendship are three, in number equal to the objects of it, since in the line of each there may be“mutual affection mutually known.”
Now they who have Friendship for one another desire one another's good according to the motive of their Friendship;accordingly they whose motive is utility have no Friendship for one another really, but only insofar as some good arises to them from one another.
And they whose motive is pleasure are in like case:I mean, they have Friendship for men of easy pleasantry, not because they are of a given character but because they are pleasant to themselves. So then they whose motive to Friendship is utility love their friends for what is good to themselves;they whose motive is pleasure do so for what is pleasurable to themselves;that is to say, not insofar as the friend beloved is but insofar as he is useful or pleasurable. These Friendships then are a matter of result:since the object is not beloved in that he is the man he is but in that he furnishes advantage or pleasure as the case may be.