Summary and Analysis
Book IX: Chapter X
While friendship is necessary for the attainment of happiness, it is superfluous and harmful to have more friends than are required to give proper scope to one's life. The ideal number of friends cannot be fixed abstractly, but in general it should be the largest number with whom one can be intimate, because intimacy is the surest guarantee of true friendship. True friendship is only possible with a small number of people since it is impossible to sympathize with the joys and sorrows of more than a few people, and affection and warmth are feelings that are too intense to be held toward more than a few. Friendships should be formed on the basis of character, virtue, and conduct, and one should make sure that his friends are all friendly with each other.