Modern systems theory provides a new paradigm for the analysis of society. In this volume, Niklas Luhmann, its leading exponent, explores its implications for our understanding of law. Luhmann argues that current thinking about how law operates within a modern society is seriously deficient. In this volume he lays out the theoretical and methodological tools that, he argues, can advance our understanding of contemporary society and, in particular, of the identity, performance, and function of the legal system within that society. In systems theory, society is its communications: they are its empirical reality; the items that can be observed and studied. Systems theory identifies how communications operate within a physical world and how different sub-systems of communication operate alongside each other. In this volume, Luhmann uses systems theory to address a question central to legal theory: what differentiates law from other parts of society? However, unlike conventional legal theory, this volume seeks to provide an answer in terms of a general social theory: a methodology that answers this question in a manner applicable not only to law, but also to all the other complex and highly differentiated systems within modern society, such as politics, the economy, religion, the media, and education. This truly sociological approach offers profound insights into the relationships between law and all of these other social systems.