The Complete Aristotle (eng.)

also without qualification pleasant,
and these are the most lovable qualities. Love and friendship
therefore are found most and in their best form between such
men.
    But it is natural that such friendships should be infrequent;
for such men are rare. Further, such friendship requires time and
familiarity; as the proverb says, men cannot know each other till
they have ‘eaten salt together’; nor can they admit each other to
friendship or be friends till each has been found lovable and been
trusted by each. Those who quickly show the marks of friendship to
each other wish to be friends, but are not friends unless they both
are lovable and know the fact; for a wish for friendship may arise
quickly, but friendship does not.
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4
    This kind of friendship, then, is perfect both in respect of
duration and in all other respects, and in it each gets from each
in all respects the same as, or something like what, he gives;
which is what ought to happen between friends. Friendship for the
sake of pleasure bears a resemblance to this kind; for good people
too are pleasant to each other. So too does friendship for the sake
of utility; for the good are also useful to each other. Among men
of these inferior sorts too, friendships are most permanent when
the friends get the same thing from each other (e.g. pleasure), and
not only that but also from the same source, as happens between
readywitted people, not as happens between lover and beloved. For
these do not take pleasure in the same things, but the one in
seeing the beloved and the other in receiving attentions from his
lover; and when the bloom of youth is passing the friendship
sometimes passes too (for the one finds no pleasure in the sight of
the other, and the other gets no attentions from the first); but
many lovers on the other hand are constant, if familiarity has led
them to love each other’s characters, these being alike. But those
who exchange not pleasure but utility in their amour are both less
truly friends and less constant. Those who are friends for the sake
of utility part when the advantage is at an end; for they were
lovers not of each other but of profit.
    For the sake of pleasure or utility, then, even bad men may be
friends of each other, or good men of bad, or one who is neither
good nor bad may be a friend to any sort of person, but for their
own sake clearly only good men can be friends; for bad men do not
delight in each other unless some advantage come of the
relation.
    The friendship of the good too and this alone is proof against
slander; for it is not easy to trust any one talk about a man who
has long been tested by oneself; and it is among good men that
trust and the feeling that ‘he would never wrong me’ and all the
other things that are demanded in true friendship are found. In the
other kinds of friendship, however, there is nothing to prevent
these evils arising. For men apply the name of friends even to
those whose motive is utility, in which sense states are said to be
friendly (for the alliances of states seem to aim at advantage),
and to those who love each other for the sake of pleasure, in which
sense children are called friends. Therefore we too ought perhaps
to call such people friends, and say that there are several kinds
of friendship-firstly and in the proper sense that of good men qua
good, and by analogy the other kinds; for it is in virtue of
something good and something akin to what is found in true
friendship that they are friends, since even the pleasant is good
for the lovers of pleasure. But these two kinds of friendship are
not often united, nor do the same people become friends for the
sake of utility and of pleasure; for things that are only
incidentally connected are not often coupled together.
    Friendship being divided into these kinds, bad men will be
friends for the sake of pleasure or of utility, being in this
respect like each other, but good men will be friends for their own
sake, i.e. in virtue of their goodness. These, then, are friends
without qualification; the others are friends incidentally and
through a resemblance to these.
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    As in regard to the virtues some men are called good in respect
of a state of character, others in respect of an activity, so too
in the case of friendship; for those who live together delight in
each other and confer benefits on each other, but those who are
asleep or locally separated are not performing, but