The sixteen essays written in honour of Jonathan Barnes for this volume reflect the impressive scope of his contributions to philosophy. Six are on knowledge, five on logic and metaphysics, five on ethics. The volume ranges widely over ancient philosophy, while also finding room for for two contemporary papers on truth (by I.Rumfitt) and vagueness (by S.Bobzien). Aristotle is prominent in eight of the essays; Plato, Sextus Empiricus, the Stoics, the Epicureans, and ancient Greek medical writers are also discussed. The contributors include some of the most distinguished scholars of our time.