Communism is a social structure and political ideology in which property is commonly controlled. Communism (written with a capital C) is a modern political movement that aims to overthrow capitalism via revolution to create a classless society where all goods are publicly owned. Karl Marx posited that communism would be the final stage in human society, which would be achieved through a proletarian revolution and only becoming possible after a socialist stage develops the productive forces, leading to a superabundance of goods and services.
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Source: http://en.wikipedia.org/wiki/Communism