I just feel like posting this to remind myself...
There are 3 kinds of friendships (based on Aristotle's Theory)...
1. Friendship for Utility
2. Friendship for Pleasure
3. Friendship for Goodness
The three types of friendships are kinda self-explanatory. But the following was what is/was written in the website....
Friendship for Utility.Utility is an impermanent things: it changes according to circumstances. So with the disappearance of the ground for friendship, the friendship also breaks up, because that was what kept it alive.
Friendships of this kind seem to occur most frequently between the elderly (because at their age what they want is not pleasure but utility) and those in middle or early life who are pursuing their own advantage. Such persons do not spend much time together, because sometimes they do not even like one another, and therefore feel no need of such an association unless they are mutually useful. For they take pleasure in each other’s company only in so far as they have hopes of advantage from it. Friendships with foreigners are generally included in this class.
Friendship for Pleasure.Friendship between the young is thought to be grounded on pleasure, because the lives of the young are regulated by their feelings, and their chief interest is in their own pleasure and the opportunity of the moment.
With advancing years, however, their tastes change too, so that they are quick to make and to break friendships; because their affection changes just as the things that please them do and this sort of pleasure changes rapidly.
Also the young are apt to fall in love, for erotic friendship is for the most part swayed by the feelings and based on pleasure. That is why they fall in and out of friendship quickly, changing their attitude often within the same day.
But the young do like to spend the day and live together, because that is how they realize the object of their friendship.
Friendship for GoodnessOnly the friendship of those who are good, and similar in their goodness, is perfect.
For these people each alike wish good for the other qua good, and they are good in themselves. And it is those who desire the good of their friends for the friends’ sake that are most truly friends, because each loves the other for what he is, and not for any incidental quality.
Accordingly the friendship of such men lasts so long as they remain good; and goodness is an enduring quality. Also each party is good both absolutely and for his friend, since the good are both good absolutely and useful to each other.
Similarly they please one another too; for the good are pleasing both absolutely and to each other; because everyone is pleased with his own conduct and conduct that resembles it, and the conduct of good men is the same or similar.
Friendship of this kind is permanent, reasonably enough; because in it are united all the attributes that friends ought to possess. For all friendship has as its object something good or pleasant — either absolutely or relatively to the person who feels the affection — and is based on some similarity between the parties.
But in this friendship all the qualities that we have mentioned belong to the friends themselves; because in it there is similarity, etc.; and what is absolutely good is also absolutely pleasant; and these are the most lovable qualities. Therefore it is between good men that both love and friendship are chiefly found and in the highest form.
That such friendships are rare is natural, because men of this kind are few. And in addition they need time and intimacy; for as the saying goes, you cannot get to know each other until you have eaten the proverbial quantity of salt together. Nor can one man accept another, or the two become friends, until each has proved to the other that he is worthy of love, and so won his trust. Those who are quick to make friendly advances to each other have the desire to be friends, but they are not unless they are worthy of love and know it. The wish for friendship develops rapidly, but friendship does not.
Aristotle The Nichomachean Ethics, 1155a3, 1156a16-1156b23 http://www.infed.org/biblio/friendship.htm