International relations theory is a diverse and constantly evolving area of scholarly research reflecting the fluctuations in world politics. This volume brings together a number of the most important research papers published on this subject during the last sixty years. Divided into five thematic sections, this work provides the reader with a comprehensive overview of developments and debates in this area of study. Topics covered include the history and development of alternative approaches to international relations theory; the importance of domestic politics in shaping a state's foreign policy; the absence of a global 'government' and the meaning and implications of this 'state of international anarchy'; power and its role as a variable in international relations theory and the challenges of state security, war and peace. The introduction anchors the collection, putting the articles within the context of the evolution of this field to date.