Superficially, Wittgenstein and Heidegger seem worlds apart: they worked in different philosophical traditions, seemed mostly ignorant of one another's work, and Wittgenstein's terse aphorisms in plain language could not be farther stylistically from Heidegger's difficult prose. Nevertheless, Wittgenstein's Philosophical Investigations and Heidegger's Being and Time share a number of striking parallels. In particular, this book shows that both authors manifest a similar concern with authenticity. David Egan develops this position in three stages. Part One explores the emphasis both philosophers place on the everyday, and how this emphasis brings with it a methodological focus on recovering what we already know rather than advancing novel theses. Part Two argues that the dynamic of authenticity and inauthenticity in Being and Time finds homologies in Philosophical Investigations. Here Egan particularly articulates and defends a conception of authenticity in Wittgenstein that emphasizes the responsiveness and reciprocity of play. Part Three considers how both philosophers' conceptions of authenticity apply reflexively to their own work: each is concerned not only with the question of what it means to exist authentically but also with the question of what it means to do philosophy authentically. For both authors, the problematic of authenticity is intimately linked to the question of philosophical method.