The Complete Aristotle (eng.)

seem to bear goodwill to each
other; but how could one call them friends when they do not know
their mutual feelings? To be friends, then, the must be mutually
recognized as bearing goodwill and wishing well to each other for
one of the aforesaid reasons.
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3
    Now these reasons differ from each other in kind; so, therefore,
do the corresponding forms of love and friendship. There are
therefore three kinds of friendship, equal in number to the things
that are lovable; for with respect to each there is a mutual and
recognized love, and those who love each other wish well to each
other in that respect in which they love one another. Now those who
love each other for their utility do not love each other for
themselves but in virtue of some good which they get from each
other. So too with those who love for the sake of pleasure; it is
not for their character that men love ready-witted people, but
because they find them pleasant. Therefore those who love for the
sake of utility love for the sake of what is good for themselves,
and those who love for the sake of pleasure do so for the sake of
what is pleasant to themselves, and not in so far as the other is
the person loved but in so far as he is useful or pleasant. And
thus these friendships are only incidental; for it is not as being
the man he is that the loved person is loved, but as providing some
good or pleasure. Such friendships, then, are easily dissolved, if
the parties do not remain like themselves; for if the one party is
no longer pleasant or useful the other ceases to love him.
    Now the useful is not permanent but is always changing. Thus
when the motive of the friendship is done away, the friendship is
dissolved, inasmuch as it existed only for the ends in question.
This kind of friendship seems to exist chiefly between old people
(for at that age people pursue not the pleasant but the useful)
and, of those who are in their prime or young, between those who
pursue utility. And such people do not live much with each other
either; for sometimes they do not even find each other pleasant;
therefore they do not need such companionship unless they are
useful to each other; for they are pleasant to each other only in
so far as they rouse in each other hopes of something good to come.
Among such friendships people also class the friendship of a host
and guest. On the other hand the friendship of young people seems
to aim at pleasure; for they live under the guidance of emotion,
and pursue above all what is pleasant to themselves and what is
immediately before them; but with increasing age their pleasures
become different. This is why they quickly become friends and
quickly cease to be so; their friendship changes with the object
that is found pleasant, and such pleasure alters quickly. Young
people are amorous too; for the greater part of the friendship of
love depends on emotion and aims at pleasure; this is why they fall
in love and quickly fall out of love, changing often within a
single day. But these people do wish to spend their days and lives
together; for it is thus that they attain the purpose of their
friendship.
    Perfect friendship is the friendship of men who are good, and
alike in virtue; for these wish well alike to each other qua good,
and they are good themselves. Now those who wish well to their
friends for their sake are most truly friends; for they do this by
reason of own nature and not incidentally; therefore their
friendship lasts as long as they are good-and goodness is an
enduring thing. And each is good without qualification and to his
friend, for the good are both good without qualification and useful
to each other. So too they are pleasant; for the good are pleasant
both without qualification and to each other, since to each his own
activities and others like them are pleasurable, and the actions of
the good are the same or like. And such a friendship is as might be
expected permanent, since there meet in it all the qualities that
friends should have. For all friendship is for the sake of good or
of pleasure-good or pleasure either in the abstract or such as will
be enjoyed by him who has the friendly feeling-and is based on a
certain resemblance; and to a friendship of good men all the
qualities we have named belong in virtue of the nature of the
friends themselves; for in the case of this kind of friendship the
other qualities also are alike in both friends, and that which is
good without qualification is