This book explores a democratic theory of international law. Characterised by a back-and-forth between theory and practice, it explores the question from two perspectives: a theoretical level which reflects and criticizes the categories, words and concepts through which international law is understood, and a more applied level focussing on ''cosmopolitan building sites'' or the practical features of the law, such as the role of civil society in international organisations or reform of the UN Security Council. Though written for an academic audience, it will have a more general appeal and be of interest to all those concerned with how international governance is developing.