Most of the 14 essays in this collection derive from a conference on the philosophical foundations of the nature of law held at McMaster University in May 2011. The philosophical foundations of the nature of law is a demanding and wide-ranging theme and, to help orient the reader, editors Wil Waluchow and Stefan Sciaraffa have written a helpful introduction and grouped the papers together by four broad themes (Furthering Debates Between Leading Theories of Law; The Power of Legal Systems; Conceptual Analysis; and New Directions). In moving from one essay to the next it is nonetheless difficult at times to keep in mind the overarching rationale for the collection, not only because the authors often approach the theme of the nature of law with different sets of methodological and conceptual assumptions, but also because many of the essays only address the question of the nature of law in an oblique manner. Despite this, the essays are of high quality and confront important issues in contemporary jurisprudence. In this review I focus most upon those essays that provide direct responses to the question of the nature of law.