“For friendship is some sort of excellence or virtue, or involves virtues, and it is, moreover, most indispensable for life. No one would choose to live without friends, even if he had all other goods. Rich men and those who hold office and power are, above all others, regarded as requiring friends. For what good would their prosperity do them if it did not provide them with the opportunity for good works? And the best works done and those which deserve the highest praise are those that are done to one’s friends. How could prosperity be safeguarded and preserved without friends? Also, in poverty and all other kinds of misfortune men believe that their only refuge consists in their friends. Friends help young men avoid error; to older people they give the care and help needed to supplement the failing powers of action which infirmity brings in its train; and to those in their prime they give the opportunity to perform noble actions. Also, it seems that nature implants friendship in a parent for its offspring and in offspring for its parent.”

Nichomachean Ethics: Book VIII, Aristotle

Philia, the Greek work for friendship, may best be summed up by the phrase “friends hold in common what they have”.

Aristotle goes on to describe three types of friendship: utility, pleasure, and virtue.

Friendships of utility are based on the good each friend is accruing for one another. If the utility of the relationship stagnates it is not uncommon to see the friendship fizzle out.

Friendships of pleasure seem to happen most often to young people, since much of their lives are driven by emotion and pursuit of what is pleasant. As such, as they advance in years and different things become pleasant friendships that were quick to form are just as quick to dissolve.

“The perfect form of friendship”, Aristotle writes, “is that between good men who are alike in excellence or virtue. For these friends wish alike for one another’s good because they are good men and they are intrinsically good. Those who wish for their friends’ good for their friends’ sake are friends in the truest sense, since their attitude is determined by what their friends are and not by incidental considerations. Hence their friendship lasts as long as they are good, and goodness or virtue is a thing that lasts.”

This third type of friendship, based on virtue, goodness, or excellence, are the relationships that, once found, should be cherished and doubled down on. Those are the friendships that can last decades.