This book offers a philosophical analysis of the role played by legal scholarship in the written judicial decisions of different Western legal systems. Based on a positivist (and, more specifically, Hartian) theory of law, the book discusses the concept of a source of law and the possibility of including within that concept the writings of legal scholars. It also discusses the concept of authority and the structure of authority-based arguments, such as those that judges often employ when referring to legal scholarship in their judgments. This book offers a philosophical analysis of the role played by legal scholarship in the written judicial decisions of different Western legal systems. Based on a positivist (and, more specifically, Hartian) theory of law, the book discusses the concept of a source of law and the possibility of including within that concept the writings of legal scholars. It also discusses the concept of authority and the structure of authority-based arguments, such as those that judges often employ when referring to legal scholarship in their judgments. Fábio Perin Shecaira, Universidade Federal do Rio de Janeiro (UFRJ), Faculty of Law, Brazil