Friendship excels mere acquaintanceship in this, that whereas you may eliminate affection from acquaintanceship,
You cannot do so from friendship.

Without affection, acquaintanceship still exists in name;
But friendship does not.

You may best understand friendship by considering that, whereas merely social ties uniting people are indefinite.

Friendship is a tie concentrated into affection, which is the bond one shares most deeply only with a few.

And now we can try to define friendship, as: enjoyment of the other’s company, accord on many things, mutual goodwill and liking.

With the exception of wisdom, I am inclined to think nothing better than this can be found in human experience.

There are people who give the palm to riches or to good health, or to power and office;
Many give the name of the best thing in life to sensual pleasures.

But all these we may say 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. And that is a noble doctrine.

But the very virtue they talk of is the parent and preserver of friendship, and without it,

Friendship cannot exist.

Concord 2:4-15