A topic of moral philosophy much discussed by Plato, Aristotle, and the Stoics, but less so in the modern era, until the reemergence of contextualist and feminist approaches to ethics. In friendship an ‘openness’ of each to the other is found that can be seen as an enlargement of the self. Aristotle writes that ‘the excellent person is related to his friend in the same way as he is related to himself, since a friend is another self; and therefore, just as his own being is choiceworthy for him, the friend’s being is choiceworthy for him in the same or a similar way.’ It is notable that friendship requires sentiments to which Kant denies moral importance. It runs counter to the universalistic requirement of impartial treatment of all, for a friend is someone who is treated differently from others. One problem is to reconcile these apparently conflicting requirements.