of theory he delved into was in connection with the Cheng Feng movement of 1942. Here, Mao summarised the correlation between Marxist theory and Chinese practice: "The target is the Chinese revolution, the arrow is Marxism–Leninism. We Chinese communists seek this arrow for no other purpose than to hit the target of the Chinese revolution and the revolution of the east". The only new emphasis was Mao's concern with two types of subjectivist deviation: (1) dogmatism, the excessive reliance upon abstract theory; (2) empiricism, excessive dependence on experience. Post-Civil War period (1949–1976) To Mao, the victory of 1949 was a confirmation of theory and practice. "Optimism is the keynote to Mao's intellectual orientation in the post-1949 period". Mao assertively revised the theory to relate it to the new practice of socialist construction. These revisions are apparent in the 1951 version of On Contradiction. "In the 1930s, when Mao talked about contradiction, he meant the contradiction between subjective thought and objective reality. In Dialectal Materialism of 1940, he saw idealism and materialism as two possible correlations between subjective thought and objective reality. In the 1940s, he introduced no new elements into his understanding of the subject-object contradiction. In the 1951 version of On Contradiction, he saw contradiction as a universal principle underlying all processes of development, yet with each contradiction possessed of its own particularity". Differences from Marxism Maoism and Marxism differ in how the proletariat is defined and in which political and economic conditions would start a communist revolution. For Karl Marx, the proletariat was the urban working class, which was determined in the revolution by which the bourgeoisie overthrew feudalism. For Mao Zedong, the proletariat was the millions of peasants he referred to as the popular masses. Mao based his revolution upon the peasantry. They possessed, according to him, two qualities: (i) they were poor and (ii) they were a political blank slate; in Mao's words, "[a] clean sheet of paper has no blotches, and so the newest and most beautiful words can be written on it". For Marx, the proletarian revolution was internally fuelled by the capitalist mode of production; as capitalism developed, "a tension arises between the productive forces and the mode of production". The political tension between the productive forces (the workers) and the owners of the means of production (the capitalists) would be an inevitable incentive for the proletarian revolution, resulting in a communist society.