Book 7.12
It is possible, then, to give something to the wise man, although all things belong to the wise man. Similarly, though we declare that friends have all things in common, it is nevertheless possible to give something to a friend: for I have not everything in common with a friend in the same manner as with a partner, where one part belongs to him, and another to me, but rather as a father and a mother possess their children in common when they have two, not each parent possessing one child, but each possessing both. First of all I will prove that any chance would-be partner of mine has nothing in common with me: and why? Because this community of goods can only exist between wise men, who are alone capable of friendship: other men can neither be friends nor partners one to another. In the next place, things may be owned in common in various ways. The knights' seats in the theatre belong to all the Roman knights; yet of these the seat which I occupy becomes my own, and if I yield it up to any one, although I only yield him a thing which we own in common, still I appear to have given him something. Some things belong to certain persons under particular conditions. I have a place among the knights, not to sell, or to let, or to dwell in, but simply to see the spectacle from, wherefore I do not tell an untruth when I say that I have a place among the knights' seats. Yet if, when I come into the theatre, the knights' seats are full, I both have a seat there by right, because I have the privilege of sitting there, and I have not a seat there, because my seat is occupied by those who share my right to those places. Suppose that the same thing takes place between friends; whatever our friend possesses, is common to us, but is the property of him who owns it; I cannot make use of it against his will. "You are laughing at me," say you; "if what belongs to my friend is mine, I am able to sell it." You are not able; for you are not able to sell your place among the knights' seats, and yet they are in common between you and the other knights. Consequently, the fact that you cannot sell a thing, or consume it, or exchange it for the better or the worse does not prove that it is not yours; for that which is yours under certain conditions is yours nevertheless.