Freudo-Marxism is a loose designation of several twentieth-century critical theory schools of thought that sought to synthesize the philosophy and political economy of Karl Marx with the psychoanalytic theory of Sigmund Freud. While the movement to integrate socialist and psychoanalytic theory has taken several forms, each arose during the middle of the twentieth century in the hope of answering this question: why did Fascism have mass appeal? The fact of that appeal confounded much of orthodox Marxist thought. The gist of the answer Freudo-Marxists gave to that question is that the masses have internalized their oppression as suppression. The internalization of the upper class in the minds of the lower class is the super-ego, in the same way that crowd psychology, in particular Freud, considered the leader to work as the masses' super-ego.