Karl Marx is without question the most influential socialist thinker of the 20 th Century. His social, economic and political ideas have deeply influenced the organization of the workplace and the political aspirations of the workers and of the poor. In 1867, Marx published the first of three volumes of Capital in which he develops his idea of surplus value and exploitation, and the resulting falling rate of profit that will lead to the collapse of industrial capitalism. The emerging labour movement of the late 19 th Century and early 20 th Century found in Marx's and Engel's Communist Manifesto (1848) its purpose as the agent of a class-conscious proletariat politically aware of the conditions for its emancipation. To a large extent, the labour conflicts and unrests that resulted from the desire to overthrow capitalism progressively led governments to adopt the model of the Welfare State in the second half of the twentieth century, and to recognize trade unions as legitimate political actors.
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