Karl Heinrich Marx (5 May 1818 – 14 March 1883) was a German philosopher, sociologist, economic historian, journalist, and revolutionary socialist who developed the socio-political theory of Marxism. His ideas have since played a significant role in the development of social science and the socialist political movement. He published various books during his lifetime, with the most notable being The Communist Manifesto (1848) and Capital (1867–1894), many of which were co-written with his friend, the fellow German revolutionary socialist Friedrich Engels.
Marx's critical theory of society, known as Marxism, holds that all societies must be understood immanently, based on the forms of thought most essential to the given society, which are a reflection of the social relations of that society. For Marx, the central category of capitalist society was value, understood as objectified human labor measured by time. Marx explained that value came to mediate human social relations under capitalism based on the historically unprecedented condition of post-industrial revolution humanity in which the condition of the typical human being was that of the urban wage laborer, compelled to sell his or her labor-power to survive. At the same time, however, Marx held that capitalism brought about enormous increases in productivity, which made wage labor anachronistic and created the possibility for a higher form of human social life in which "the free development of each would be the condition for the free development of all." He believed this potential could be realized through the political struggle of the working class for socialism, which would entail the abolition of proletarian labor itself and allow humanity to freely direct its own history, rather be dominated by the alien power of capital, the drive of value to create more value, which fundamentally constrains human social life under capitalism.