Friendship is a virtue or at least involves virtue. It is necessary to life, since no one would choose to live without friends even if he had all other material goods. Friends are a refuge in times of poverty and misfortune, they help to guard the young from error, they help the old in their weakness, and help those in the prime of life to perform noble actions. Parents have a natural friendship with their children, and to a certain degree those of the same race do as well.
Friendship unites the state.
When men are friends, there is no need of justice, but when even if men are just, friendship is still necessary. Friendship is not just necessary, but also noble. In order to answer these questions, it is necessary to see what makes something likeable. The three possibilities are goodness, pleasure and usefulness. To be friends, two people need to be well-disposed toward one another and wish each other's good, and they must know that this is the case.