"Theoretical Foundations" is the first volume of the collected writings of Franz Oppenheimer, one of the founders of German sociology and a key contributor to the concept of "social market economy." This work provides a comprehensive theoretical basis for democracy and market economy, highlighting Oppenheimer's significant contributions to the social sciences. The publication is in German and spans 752 pages, containing in-depth analyses and reflections on fundamental economic and social theories. The writings, which were banned during the Third Reich, are now being made accessible again to acknowledge Oppenheimer's influence on modern sociology and economic theory. The hardcover ensures the book's durability, making it of interest to both students and professionals.