Karl Marx was a 19th century philosopher, economist, and socialist revolutionary. He developed the theory of historical materialism which argues that economic and material forces drive historical change and development. Marx believed that capitalism would inevitably create contradictions and class conflict between the bourgeoisie and proletariat, leading to revolution and establishment of a communist, classless society. Neo-Marxism emerged in the 20th century and expanded on Marx's theories to include analysis of culture, ideology, and other social factors rather than just economics. Marxist ideas and concepts like alienation, exploitation, and historical materialism continue to influence the study of society, economics, history and conflict.