True Friends have one soul, Aristotle

Aristotle wonders about the nature of happiness, and in this study of happiness he focuses in three elements that identifies as keys for the happy man: the virtue, in special justice, the friendship and the pleasure.
Let's talk about the second: the friendship. Aristotle in his book Nichomaquean Ethics, Book VIII wrote about friendship: "is the most necessary for life. In effect, without friends nobody would want to live......But friendship is not is not only necessary but beautiful. We praise those who love their friends and having a lot of friends is considered one of the best things".
Then he affirms: "the happy life is considered to be the life according to virtue."
For what is exposed for Aristotle we can say that needing the man of the virtue for his social activity, and being the friends those with whom we primarity exercise the virtue; friendship is not the foundation of happiness, but without it (friendship) man can not achieve happiness. Friendship is necessary but not sufficient. We need both friendship and virtue.

Friendship is equality

Aristotle in his book Nicomachean Ethics speaks frecuently about the theme of friendship, he speaks about the mercy, "the ethical friendship"; the justice, "the general friendship; and the Concord, "the political friendship". For Aristotle friendship is not also necessary but beautiful:"friendship is equality", "the benevolence is the beginning of the friendship" expresses to us.
Friendship is equality because it is closely related to a form of love: "Philia". In the ancient greek lenguage each form of love had his own name: eros, the love of lovers, agape the love for the good and Philia. This last form of love is the love that arises from the pleasure of seeing ourselves reflected in the others. The natural love, Philia is the origine of the friendship and the equality, the likeness, among men.