This cutting-edge textbook provides a comprehensive introduction to international relations theory. Arguing that theory is central to explaining the dynamics of world politics, it includes a wide variety of theoretical positions--from the historically dominant traditions to powerful critical voices since the 1980s. The editors have brought together a team of international contributors, each specializing in a different theory. The contributors explain the theoretical background to their positions before showing how and why their theories matter. The book opens up space for analysis and debate, allowing students to decide which theories they find most useful in explaining and understanding international relations.