More than 50 years after it was first published, HLA Hart's The Concept of Law remains the most important work of legal philosophy in the English-speaking world. In this volume, written for both students and specialists, 13 leading scholars look afresh at Hart's great book. Unique in format, the book proceeds sequentially through all the main ideas in The Concept of Law, with each contributor addressing a single chapter of Hart's book and critically discussing its arguments in light of subsequent developments in the field. Four concluding essays assess the continued relevance for jurisprudence of the 'persistent questions' identified by Hart at the beginning of The Concept of Law. This book will be essential reading for all those interested in HLA Hart, as well as all those interested in legal philosophy more generally.