1. Introduction: differentiation theory and international relations Mathias Albert, Barry Buzan and Michael Zurn Part I. Sociological Perspectives: 2. Rationalized cultural contexts of functional differentiation George M. Thomas 3. The history and systematics of functional differentiation in sociology Rudolf Stichweh 4. Functional, segmentary, and stratificatory differentiation of world society Richard Munch Part II. On the Differentiated Structure of the International System: 5. Differentiation: type and dimension approaches Jack Donnelly 6. Stratificatory differentiation as a constitutive principle of the international system Lora Anne Viola 7. Some quanta of solace: world politics in the era of functional differentiation Stephan Stetter Part III. On the Interplay of (Global) Function Systems: 8. Functional differentiation and the oughts and musts of international law Oliver Kessler and Friedrich Kratochwil 9. International institutions in a functionally differentiated world society Mathias Koenig-Archibugi 10. Functional differentiation, globalization and the new transnational neo-pluralism Philip G. Cerny 11. Conclusion: differentiation theory and world politics Michael Zurn, Barry Buzan and Mathias Albert.