Oskar Lange was one of the few economists able to observe first hand the three major economic systems that have been the hallmark of the 20th century. He learned about the economic backwardness of peripheral capitalism in pre-war Poland. Later he spent more than twelve years in the bastion of modern capitalism, the United States. After returning to Poland in 1948 he linked his fate to the creation and then reform of the Communist system.This important collection of Professor Lange's work, prepared by his disciple and close friend Tadeusz Kowalik, presents his most important work on the economic theory of socialism, economic planning, Marxism and 'bourgeois' economics. The volume makes an important contribution by improving access to the papers of an economist whose work was at the very heart of the intellectual conflict between socialism and capitalism in the late twentieth century.