What does it mean to assert or deny the existence of a legal system? How can one determine whether a given law belongs to a certain legal system? What kind of structure do these systems have, that is-what necessary relations obtain between their laws? The examination of these problems in this volume leads to a new approach to traditional jurisprudential question, though the conclusions are based on a critical appraisal, particularly those of Bentham, Austin, Kelsen, and Hart.