Labor law has always been preoccupied with boundaries. One can either be an "employee" or not, an "employer" or not, and the answer dictates who comes within the scope of labor law, for better or worse. But such divisions have always been difficult, and in recent years their shortcomings have become ever more pronounced. The proliferation of new work arrangements and heightened global competition has exposed a world-wide crisis in the regulation of work. It is therefore timely to re-assess the idea of labor law, and the concepts, in particular, the age-old distinctions that are used to delimit the field. This collection of essays, by leading experts from around the world, explores the frontiers of our understanding of labor law itself.