This highly successful textbook provides a systematic introduction to the principle theories in international relations. It combines incisive and original analysis with a clear and accessible writing style, making it the ideal textbook for all students taking an introductory course in international relations or international relations theory. The book focuses on the main theoretical traditions - Realism, Liberalism, International Society, and theories of international political economy. The third edition includes two new chapters on Social Constructivism and foreign policy. Emphasis is placed on the relationship between IR theory (academic knowledge of IR) and IR practice (real world events and activities of world politics). The authors carefully explain how particular theories organize and sharpen our view of the world. The book is supported by an Online Resource Centre. Student resources: Case studies with assignments Review questions Web links to theoretical debates, maps and world situations (NEW) Flashcard glossary (NEW) Lecturer resources: Figures and tables from the text (NEW)