Marx primarily worked in economics and political philosophy. He is most famous for his development of Communism and Marxism. He developed a theory of ‘historical materialism,’ sometimes called ‘dialectical materialism,’ which argues that material conditions shape history and society; he critiqued capitalism in its extraction of surplus value; he identified and analyzed the nature of class struggle; and theorized upon future communist and socialist revolutions.

His major works are The Communist Manifesto and Capital, though different reading orders are frequently argued for.