In Friendship, James O. Grunebaum introduces a new conceptual framework to articulate, explain, and understand similarities and differences between various conceptions of friendship. Asking whether special preference for friends is morally justified, Grunebaum answers that question by analyzing a comprehensive comparison of not only Aristotle's three well-known kinds of friendship—pleasure, utility, and virtue—but also a variety of lesser-known friendship conceptions from Kant, C. S. Lewis, and Montaigne. The book clarifies differences about how friends ought to behave toward each other and how these differences are, in part, what separate the various conceptions of friendship.