Michel Foucault was a French philosopher, historian of ideas, social theorist, and literary critic. American economist, social theorist, political philosopher, and author Thomas Sowell is also an alumnus. He is an outspoken anarchist and conspiracy theorist. Hayek was also a major social theorist and political philosopher of the 20th century. Vygotsky was a Russian theorist, who proposed the sociocultural theory. The British military armor theorist and historian, Capt. He is a conspiracy theorist and firearms enthusiast. Poulantzas has been particularly influential over the leading contemporary Marxist state theorist, Bob Jessop. Althusser is also widely known as a theorist of ideology. A key early socialist theorist of political economy was Pierre-Joseph Proudhon. Hess became friends with Haushofer and his son Albrecht, a social theorist and lecturer. Smith is an avid "conspiracy theorist" and his statements often generate controversy. He also read "", the 1867 book by German sociological theorist Karl Marx. Lazar has achieved notoriety as an Area 51 conspiracy theorist. Its co-founders included Richard Florida, urban theorist and professor.