Do theories of world society provide viable alternatives to the notion of an 'international system'? Observing International Relations draws upon the modern systems theory of society, developed by Niklas Luhmann, to provide new perspectives on central aspects of contemporary world society and to generate theoretically informed insights on the possibilities and limits of regulation in global governance. The authors develop a Luhmannian theory of world society by contrasting it with competing notions of international society, critically discussing the use of modern systems theory in international relations theory and assessing its treatment of central concepts within international relations, such as power, sovereignty, governance and war. The book will appeal to both sociologists and international relations specialists interested in the application of sociological theories to social contexts beyond the nation state. Mathias Albert, University of Bielefeld, Germany Lothar Brock, Johann Wolfgang Goethe University, Germany Chris Brown, London School of Economics, UK Thomas Diez,