A collected edition of Longfield's economic contributions with an introduction and bibliography by R.D. Collison-Black. Lectures on Political Economy (1834) formulated a theory of profits determined by the marginal productivity of physical capital and a theory of wages determined by the specific productivity of the laborer. In Lectures on Commerce (1833) Longfield anticipated several later developments in international trade theory. "The three volumes of lectures ... have since been recognized as containing contributions to economic theory of outstanding originality." The New Palgrave . "He overhauled the whole of economic theory and produced a system that would have stood up well in 1890." J.A. Schumpeter History of Economic Analysis