Landheer, B. Keywords: Sociology | International law | Mots clefs: Sociologie | Droit international | ABSTRACT After a few remarks on the fundamental concepts of sociology, B. Landheer studies the evolution of sociological thinking related to international society and international law. He then focuses on the relations between formal and non-formal structure in international society. He discusses the impact of social change on international society. Finally, the author discusses the likely evolution of group fo…