The book examines the major traditions of ancient ethical theory, showing that they share a common theoretical structure. They are examples of eudaimonism, a type of ethical theory in which the basic concepts are those of happiness and virtue. The book looks at the way this type of theory is articulated in Aristotle, and then at the differing versions of it to be found in Epicurus, the Stoics, and Academic and Pyrrhonian Sceptics. We find a common structure: we all implicitly seek a final end in all our actions, but different theories offer rival accounts of what this consists in. To gain a proper understanding of the ancient debates, we have to examine the basic concepts of happiness and virtue, which in modern ethical theories are often subject to misunderstanding. The book first aims to recover the ancient understanding of these basic notions, then examines the role of nature in ancient ethical justification, the role in eudaimonism of other‐concern, and finally the extent to which the ancient theories demand revision and transformation of everyday ethical thought.