Abstract
From the very beginning of modern economic thought the importance of "effective demand" has been dominant. In the Wealth of Nations (Book I, Chapter 7) we read how supply and demand interact to form market price. From the time of Adam Smith to the present, this emphasis has received greater and greater refinement. This study will isolate just one-half of this price theory, namely, the theory of demand, and trace its development from the neoclassical formulation of Alfred Marshall in 1890 through the additions of Chamberlin and Robinson, the refinements of Hicks and Norris, the "new directions" of Keynes and his followers, the experiments of Schultz and the econometricians, to the status of present-day demand theory.