Oskar Lange lectured at the University of Cracow, the University of California, and the University of Chicago. He published numerous books and articles in Polish, German, and English on the problems of economic theory. Fred M. Taylor, a distiguished American economist, was professor at the University of Michigan from 1904 until his death in 1932. He is the author of Principles of Economics and other volumes. The paper reprinted herewith was his presidential address to the American Economic Association in 1928. Benjamin E. Lippincott, the editor of this volume, was professor of political science at the University of Minnesota. He is the author of Victorian Critics of Democracy, published by the University of Minnesota Press in 1938.