To a friend, however, it is said, you must wish goods for his own sake. If you wish good things in this way, but the same wish is not returned by the other, you would be said to have [only] goodwill for the other. For friendship is said to be reciprocated goodwill.
[I]t is possible for bad people as well [as good] to be friends to each other for pleasure or utility, for decent people to be friends to base people, and for someone with neither character to be a friend to someone with any character. Clearly, however, only good people can be friends to each other because of the other person himself; for bad people find no enjoyment in one another if they get no benefit.
In all the friendships that rest on superiority, the loving must also be proportional; for instance, the better person, and the more beneficial, and each of the others likewise, must be loved more than he loves; for when the loving accords with the comparative worth of the friends, equality is achieved in a way.