Aristotle, Nicomachean Ethics
H. Rackham, Ed.

wishes his own good: no one would choose to possess every good in the world on condition of becoming somebody else （for God possesses the good even as it is）,¹ but only while remaining himself, whatever he may be; and it would appear that the thinking part is the real self, or is so more than anything else. [5] And （c） the good man desires his own company; for he enjoys being by himself, since he has agreeable memories of the past, and good hopes for the future, which are pleasant too; also his mind is stored with subjects for contemplation. And （e） he is keenly conscious of his own joys and sorrows; for the same things give him pleasure or pain at all times, and not different things at different times, since he is not apt to change his mind.

It is therefore because the good man has these various feelings towards himself, and because he feels towards his friend in the same way as towards himself （for a friend is another self） , that friendship also is thought to consist in one or other of these feelings, and the possession of them is thought to be the test of a friend. [6]

Whether a man can be said actually to feel friendship for himself is a question that may be dismissed for the present; though it may be held that he can do so in so far² as he is a dual or composite being,