What is liberty, as opposed to license, and why is it so important? When people pursue happiness, peace and prosperity whilst living in society, they confront pervasive problems of knowledge, interest, and power. These problems are dealt with by ensuring the liberty of the people to pursue their own ends, but addressing these problems also requires that liberty be structured by certain rights and procedures associated with the classical liberal conception of justice and the rule of law. Drawing upon insights from philosophy, economics, political theory, and law, Randy Barnett examines the serious social problems that are addressed by liberty--and the background or "natural" rights and "rule of law" procedures that distinguish liberty from license. He then outlines the constitutional framework that is needed to protect this structure of liberty. Athough this controversial new work is intended to challenge specialists, its clear and accessible prose ensure that it will be of immense value to both scholars and students working in a range of academic disciplines.