How we cite our quotes: (Book.Chapter.Bekker #s); all Bekker line numbers are approximate, since they are keyed to the original Greek.
Quote #4
Those who love each other on account of utility, then, do not love each other in themselves, but only insofar as they come to have something good from the other. Similar too is the case of those who love on account of pleasure, for people are fond of those who are witty, not because they are of a certain sort, but because they are pleasant to them. (8.3.1156a10-14)
When Aristotle speaks of love in this way, he is still speaking about friendship—or rather "friendly affection," which is a kind of passion that holds us to what is lovable in another person. This can also extend to erotic relationships, but "love" in this case is not exclusively sexual. In these types of friendships, those involved don't love their friend for who they are, but rather what they bring to the relationship. And you can imagine what happens when either friend can't deliver what's expected of him.
Quote #5
These sorts of friendships, then, are easily dissolved when the people involved do no remain the same as they were. For if they are no longer pleasant or useful, those who love them will cease to do so. And what is useful does not remain constant but is different at different times. (8.3.1156a19-22)
Aristotle is speaking here of two types of false friendships, those of utility and pleasure. These relationships are entirely practical—we would call them relationships of convenience—but are less than satisfactory in terms of emotional fulfillment. They also tend to be short-lived…for the reasons mentioned. Though this is a bleak definition of friendship, Aristotle is setting us up to understand what a strong friendship (or complete friendship) looks like.
Quote #6
But complete friendship is the friendship of those who are good and alike in point of virtue. For such people wish in similar fashion for the good things for each other insofar as they are good, and they are good in themselves. (8.3.1156b7-10)
This is ideal friendship, in which each person loves the other for his "characteristics" or virtues. Because the cause of such love resides in a part of the person that changes very little over time, the friendship has very little reason to go sour—unlike the friendships based on utility and pleasure, which are unstable because they're based on inconstant things. Also—and this will be an important part of this discussion—the friends are "good in themselves," which means that are not only lovable to others, but also to themselves.