 Aristotle attempts to answer this question in IX.11, but his treatment is disappointing. His fullest argument depends crucially on the notion that a friend is “another self”, someone, in other words, with whom one has a relationship very similar to the relationship one has with oneself. A virtuous person loves the recognition of himself as virtuous; to have a close friend is to possess yet another person, besides oneself, whose virtue one can recognize at extremely close quarters; and so, it must be desirable to have someone very much like oneself whose virtuous activity one can perceive. The argument is unconvincing because it does not explain why the perception of virtuous activity in fellow citizens would not be an adequate substitute for the perception of virtue in one’s friends.