The Importance of Friendship
Aristotle devotes two of the ten books of the Ethics to discussing friendship in all its forms. This is hardly a digression from the main line of argument. Happiness, according to Aristotle, is a public affair, not a private one, so with whom we share this happiness is of great significance.
The city-states of ancient Greece were tightly knit communities. In the Politics, Aristotle argues that we cannot fully realize our human nature outside the bounds of a Greek city-state. The bonds that tie citizens together are so important that it would be unthinkable to suggest that true happiness can be found in the life of a hermit.