The contributions included in this book, all written by renowned scholars, examine some of the long-standing fundamental issues of international law. The main part concerns the following question: how is international law made and applied? A highly original, systematic assessment of the formation of customary international law provides an answer to this question. Two other long-standing fundamental issues are also examined. The volume is concluded by a discussion on a paradoxical aspect of the law of treaties, namely regarding the right of the parties to terminate their agreements.