In contemporary discussions, ethics and inquiry into the natural world are often treated as two completely independent fields of study. By contrast, many ancient thinkers took them to be intimately connected. This volume aims to shed light on the various ways in which ancient thinkers drew connections between these two fields. We human beings are in some sense part of the natural world, and live our lives within a larger cosmos, but yet our actions are governed by norms whose relation to the natural world is up for debate. The chapters in this volume discuss how these facts about our relation to the world bear upon both ancient accounts of human goodness and also ancient accounts of the natural world itself. The chapters focus primarily on Plato and Aristotle. But we have also included some discussion of earlier and later thinkers, with a chapter on the Presocratics and a couple of chapters that at least in part point ahead to later Epicurean, Stoic, and Neoplatonist philosophers.