This book explores the history of moral thought as it has developed over three millennia, from Homer's Greece to Mao's China, from ancient India to modern America. It tells the stories of the great philosophers, and breathes life into their ideas, while also challenging many of our most cherished moral beliefs. Engaging and provocative, this book confronts some of humanity's deepest questions. Where do values come from? Is God necessary for moral guidance? Are there absolute moral truths? It also brings morality down to earth, showing how, throughout history, social needs and political desires have shaped moral thinking. It is a history of the world told through the history of moral thought, and a history of moral thought that casts new light on global history. At a time of great social turbulence and moral uncertainty, there will be few histories more important than this.