All states and political movements in the world today proclaim themselves in favor of liberty. But what precisely does it mean to say that a person or society is free? The essays collected in this book represent the best analyses of the concept of liberty offered by political theorists over the last century. They contain a wide range of views about what liberty consists of and how it may be promoted and chosen to represent the spectrum of political opinion. David Miller's introduction provides a comprehensive overview of the debate, placing recent contributions within traditions of thought about liberty that stretch back to ancient Greece. This book will be of interest to undergraduate and graduate students in politics, political theory, and political philosophy.