"What is Justice?" is a compilation of essays by Hans Kelsen that deal with problems of justice and their relationship to law, philosophy, and science. The broad scope and applicability of "What is Justice?" makes it a valuable source for research and writing across jurisdictions and in almost any area of law. Access to the English translation of "What is Justice?" is challenging because the book has no index. This present Index aims to provide scholars with a way in to Kelsen's work. Kelsen's tightly packed generalisations and conceptual arguments, which are intended to apply generally to all laws and legal systems, are not accessible to all readers. The Index attempts to present Kelsen's theories in a manner that enables readers to apply them to any area of law and to take full advantage of Kelsen's wisdom. The authors call their work an "index" because it most closely resembles that literary form. However, the work and its companion, "A Diachronic Index and Glossary to [Kelsen's] Pure Theory of Law?" attempt much more. Each has features of a concordance, and each finds conceptual links between Kelsen's insight and legal institutions and reasoning in areas of law that he never considered. A paper that uses the Indexes to examine such links is John Prebble, "Kelsen, the Principle of Exclusion of Contradictions, and General Anti-Avoidance Rules in Tax Law." / Series: WU International Taxation Research Paper Series