Knowledge, Nature, and the Good brings together some of John Cooper's most important works on ancient philosophy. In thirteen chapters that represent an ideal companion to the author's influential Reason and Emotion, Cooper addresses a wide range of topics and periods - from Hippocratic medical theory and Plato's epistemology and moral philosophy, to Aristotle's physics and metaphysics, academic scepticism, and the cosmology, moral psychology, and ethical theory of the ancient Stoics. Almost half of the pieces appear here for the first time or are presented in newly expanded, extensively revised versions. Many stand at the cutting edge of research into ancient ethics and moral psychology. Other chapters, dating from as far back as 1970, are classics of philosophical scholarship on antiquity that continue to play a prominent role in current teaching and scholarship in the field. All of the chapters are distinctive for the way that, whatever the particular topic being pursued, they attempt to understand the ancient philosophers' views in philosophical terms drawn from the ancient philosophical tradition itself (rather than from contemporary philosophy). Through engaging creatively and philosophically with the ancient texts, these essays aim to make ancient philosophical perspectives freshly available to contemporary philosophers and philosophy students, in all their fascinating inventiveness, originality, and deep philosophical merit. This book will be treasured by philosophers, classicists, students of philosophy and classics, those in other disciplines with an interest in ancient philosophy, and anyone who seeks to understand philosophy in philosophical terms.