That friends form some sort of unity is one of the remarkable facts about friendship. We identify with our friends in a way in which we do not identify with non-friends. This identification forms the foundation for the distinction that we make between friends and non-friends. Many other facts about friendship are grounded in it - such as the fact that we are willing to help friends in a way that goes beyond what is otherwise demanded by morality or custom. When our friends need someone to help them move to a new apartment, for example, we will help them without demanding anything in return; we would be rather reluctant to do the same for a stranger. So it is important to ask what sort of unity friendship possesses. In what follows, I shall argue that we find an interesting conception of this unity in Plato.