This Guide for the Perplexed offers a novel approach to international relations theory. Instead of presenting competing theories in individual chapters, the book is structured around key spheres of human existence and theoretical enquiry, including history, law, politics, morals, society, and economics. Today, many theories are offered to explicate disputes, conflicts, crises, wars, and other international problems. To help the student sort through this variety of theories, Devetak introduces a historical approach articulated around core concepts. By getting away from the overused methods of classifying international relations theory in terms of various '-isms', which implies that to be theoretical one has to approach international relations form one of these positions (realism, liberalism, socialism, etc.), Devetak can focus on the shifting and rival understandings on international relations as they develop in the context of various questions and knowledge domains. International Relations Theory will be an essential resource that will provide both students and lecturers a historically-informed account that will encourage debate.