This work provides a consistent and empirically meaningful definition of surplus and suggests an analytical framework for studying economic growth and stagnation using that concept. The book also presents a case study of the role of surplus in economic growth. In the first part of the work, a method is developed emphasizing the links to classical economic theory and the logical flaws of the earlier works. The second part examines the role of surplus in one country, and tests the classical hypotheses about growth in the long run and in a cross-section of countries.