The Situationist International (SI) was an international organization of social revolutionaries made up of avant-garde artists, intellectuals, and political theorists. It was prominent in Europe from its formation in 1957 to its dissolution in 1972. The intellectual foundations of the Situationist International were derived primarily from libertarian Marxism and the avant-garde art movements of the early 20th century, particularly Dada and Surrealism. Overall, situationist theory represented an attempt to synthesize this diverse field of theoretical disciplines into a modern and comprehensive critique of mid-20th century advanced capitalism.