Aristotle's Nicomachean Ethics is the first and arguably most important treatise on ethics in Western philosophy. It remains to this day a compelling reflection on the best sort of human life and continues to inspire contemporary thought and debate. This Companion includes twenty essays by leading scholars of Aristotle and ancient philosophy that cover the major issues of this text. The essays in this volume shed light on Aristotle's rigorous and challenging thinking on questions such as: can there be a practical science of ethics? What is happiness? Are we responsible for our character? How does moral virtue relate to good thinking? Can we act against our reasoned choice? What is friendship? Is the contemplative life the highest kind of life? Covering all sections of the Nicomachean Ethics and selected topics in Aristotle's Eudemian Ethics and Protrepticus, this volume offers the reader a solid foundation in Aristotle's ethical philosophy.