I sent out a bit from Aristotle's Nicomachean Ethics to some of my close friends. If you'd like to follow along it's from Book IX, Chapter 9, from Becker numbers 1169B30 to the end of the chapter.
Nicomachean Ethics spends the first 7 books talking about virtue of character and intellectual virtue. In Book VIII, however, Aristotle begins a discussion of "friendship". To me it's a bit of a non-sequitur, but I think if you take into account what he's seems to be saying about man as a political creature it sort of follows to discuss friendship. Now if you are familiar with this part, he identifies three sorts of friendship: friendship of utility, friendship of pleasure, and true friendship. He identifies different qualities of each and discusses a surprising variety of topics related to them, but I'm interested in where he is heading, rather than any particular specifics of friendship.
In the Sachs translations of Aristotle, there is a lot of reference to "being-at-work", translated from the Greek energeia. What he means by this that I find lacking in other translations of energeia is something like an active condition. Not something you actively maintain, but some part of being that is actively enacting.
Now if, as Aristotle thinks, "thinking" is the primary action of man and the "intellect" (Grk: nous) is something like what we would call the self, why would we need friends? Why should man desire nothing more than self reflection and introspection, which, based on the passage indicated, seems to be the greatest good. Why do we need more than the awareness of being that we have within us?
If this "being-at-work" of self is so important, what is it? How can I share in a friend's awareness that "he is"? Do you suppose Aristotle is somehow right about intellect and the self? Another section that may be helpful to read for this discussion would be Chapter 8, especially the paragraph around 1169A.
The question becomes, "What is it about my relationship with my friend that gives me a greater good than my own awareness of self?"