The concept of a social contract has been central to political thought since the 17th century. Contract theory has been used to justify political authority, to account for the origin of the state and to provide foundations for moral values and a just society. In this collection, leading scholars from Britain and America survey the history of contractarian thought and the major debates in political theory which surround the notion of social contract. They examine the critical reception of the ideas of thinkers such as Hobbes, Locke, Rousseau, Hegel and Marx, and include the more contemporary ideas of Rawls and Gauthier. The collection also incorporates discussions of international relations theory and feminist responses to contractarianism. Challenging the notion that there is a single tradition that can be traced back beyond Hobbes to classical Greece, three distinct traditions are identified, alongside a series of anti-contractarian arguments which have played a role in shaping the debate to the present day. Together, these essays aim to provide a comprehensive introduction to theories and critiques of the social contract, within a broad political theoretical framework.