Varieties of Happiness challenges the widespread belief that Greek ethics is a distinctive type of ethical theory labeled "eudaimonist", an overarching term for a range of ideas regarding human flourishing and happiness. It critically examines what it is for an ethical theory to be eudaimonist or operate within the eudaimonist framework. Plainly, if a theory is eudaimonist, then the notion of eudaimonia plays a crucial role in the theory. Iakovos Vasiliou argues, however, that although it is true that ancient philosophers discuss eudaimonia frequently, it is far less clear that it plays a role in their ethical theory that makes for a distinctive kind of ethical theory. Merely discussing what makes a human life a happy one is insufficient for a theory to be eudaimonist. Any philosopher might have views about what a happy life is, without that making their mode of ethical reasoning and deliberation distinctly eudaimonist, for example by treating eudaimonia as the ultimate goal of every action.

Vasiliou identifies and critically analyzes three further roles that eudaimonia may play, which, individually or jointly, have been thought sufficient to make a theory eudaimonist: (1) as a comprehensive practical principle; (2) as a concept that can provide content for virtuous action; and (3) as a grounding, justification, or motivation to pursue virtue. Through detailed interpretations of texts on happiness and virtue from Plato's Socratic dialogues The Republic and Symposium, Aristotle's Nicomachean Ethics, Epicurus, and the early Stoics, this book invites us to revise our understanding of ancient ethics.