Now this truth seems clear to me, that nature has so formed us that
a certain tie unites us all, but that this tie becomes stronger from
proximity. So it is that fellow-citizens are preferred in our
affections to foreigners, relations to strangers; for in their case
Nature herself has caused a kind of friendship to exist, though it is
one which lacks some of the elements of permanence. Friendship
excels relationship in this, that whereas you may eliminate
affection from relationship, you cannot do so from friendship.
Without it relationship still exists in name, friendship does not.
You may best understand this friendship by considering that,
whereas the merely natural ties uniting the human race are
indefinite, this one is so concentrated, and confined to so narrow a
sphere, that affection is ever shared by two persons only or at most
by a few.

6. Now friendship may be thus defined: a complete accord on all
subjects human and divine, joined with mutual goodwill and
affection. And with the exception of wisdom, I am inclined to
think nothing better than this has been given to man by the
immortal gods. There are people who give the palm to riches or to
good health, or to power and office, many even to sensual
pleasures. This last is the ideal of brute beasts; and of the others
we may say that they are frail and uncertain, and depend less on
our own prudence than on the caprice of fortune. Then there are
those who find the "chief good" in virtue. Well, that is a noble
doctrine. But the very virtue they talk of is the parent and
preserver of friendship, and without it friendship cannot possibly
exist.

Let us, I repeat, use the word virtue in the ordinary acceptation and