To have a friend is to have another self; it is concord and harmony, which nothing can equal.
In this,one is the equivalent of many. For if two, or ten, are united, none of them is merely one any longer, but each of them has the ability and value of ten; and you will find the one on the ten, and the ten in the one. If they have an enemy, attacking not one, but ten, he is defeated, for he is struck, not by one, but by ten .
Has one fallen into want? Still he is not desolate; for he prospers in his greater part; that is to say in the nine, and the needy part is protected; that is, the smaller part by that which prospers.
Each one of them has twenty hands, and twenty eyes, and as many feet. For he sees not with his own eyes alone, but with those of others; he walks not with his own feet, but with those of others; he works not with his own hands, but with those of others. He has ten souls, for he alone is not concerned about himself, but those other nine souls are concerned about him.
And if they are a hundred, the same thing will take place again, power will be increased.
-St Anthusa, the mother of St John Chrysostom, in a letter to her son, “On Ideal Friendship”