Hans Kelsen is considered by many to be the foremost legal thinker of the twentieth century. During the last decade of his life he was working on what he called a general theory of norms. Published posthumously in 1979 as Allgemeine Theorie der Normen, the book is here translated for the first time into English. Kelsen develops his "pure theory of law" into a "general theory of norms", and analyzes the applicability of logic to norms to offer an original and extreme position which some have called "normative irrationalism". Examining the views of over 200 philosophers and legal theorists on law, morality, and logic, and revising several of his own earlier positions, Kelsen's final work is a mandatory resource for legal and moral philosophers.