Karl Heinrich Marx (May 5, 1818 – March 14, 1883), a German philosopher, political economist, historian, political theorist, sociologist, and revolutionary socialist, who developed the socio-political theory of Marxism. His Marxist ideas influenced the development of modern social science and also in 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 is typically cited as one of the three principal architects of modern social science, along with Émile Durkheim and Max Weber. In 1999, a BBC poll revealed that Marx had been voted the "thinker of the millennium" by people from around the world.