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.