Niklas Luhmann's "Social Systems" (1984) forms the cornerstone of the system theory he developed; the work serves as an introduction to his "Theory of Society." Here, he unfolds his system-theoretical terminology, often using the same terms as in traditional terminology, but filled with different meanings in Luhmann's own social theory. The contributions in this volume provide access to Luhmann's theory and demonstrate that, like any theory, it is a construct that helps us understand reality. The authors of the collaborative commentary on Luhmann's work "Social Systems" are prominent theorists who conduct their research closely related to Luhmann's theory. In the contributions of this volume, readers will be informed about the content of the book.