Plutarch De fraterno amore 3

[3] It is true that the Arcadian prophet ¹ of necessity manufactured for himself, according to Herodotus, a wooden foot, deprived as he was of his own; but the man who quarrels with his brother, and takes as his comrade a stranger from the market-place or the wrestling-floor, appears to be doing nothing but cutting off voluntarily a limb of his own flesh and blood, and taking to himself and joining to his body an extraneous member. Indeed it is our very need, which welcomes and seeks friendship and comradeship, that teaches us to honour and cherish and keep our kin, since we are unable and unfitted by Nature to live friendless, unsocial, hermits’ lives. Wherefore Menander ² rightly says, For most friendships are in reality shadows and imitations and images of that first friendship which Nature implanted in children toward parents and in brothers toward brothers; and as for the man who does not reverence or honour this friendship, can he give any pledge of goodwill to strangers? Or what sort of man is he who addresses his comrade as brother in salutations and letters, but does not care even to walk with his own brother when they are going the same way? For as it is the act of a madman to adorn the effigy of a brother and at the same time to beat and mutilate the brother’s body, even so to reverence and honour the name brother in others, but to hate and shun the person himself, is the act of one who is not sane and has never yet got it into his head that Nature is the most holy and great of sacred things. ³

[3] The Arcadian prophet in Herodotus was forced to supply the loss of one of his feet with an artificial one made of wood. But he who in a difference throws off his brother, and out of places of common resort takes a stranger for his comrade, seems to do no less than wilfully to mangle off a part of himself, attempting to repair the barbarous breach by the unnatural application of an extraneous member. For the ordinary inclinations and desires of men, being after some sort of society or other, sufficiently admonish them to set the highest value upon relations, to pay them all becoming respects, and to have a tender regard for their persons, nothing being more irksome to nature than to live in that destitution and solitude that denies them the happiness of a friend and the privilege of communication. Well therefore was that of Menander:

For a great deal of friendship in the world is really no better and no more than the mere imitation and resemblance of that first affection that Nature wrought in parents towards their children, and in their children towards one another. And whoever has not a particular esteem and regard for this kind of friendship, I know no reason ally one has to credit his kindest pretensions. For what shall we make of that man who in his complaisance, either in company or in his letters, salutes his friend by the name of brother, and yet scorns the company of that very brother whose name was so serviceable to him in his compliment? For, as it is the part of a madman to adorn and set out the effigies of his brother, and in the mean time to abuse, beat, and maim his person; so, to value and honor the name in others but to hate and shun the brother himself is likewise an action of one that is not so well in his wits as he should be, and that never yet considered that Nature is a most sacred thing.