The problems of ideology occupy a prominent place in the system of the social philosophy of the Frankfurt School. The concept of ideology figures in all the works of the "Frankfurtists," alongside such categories as "alienation," "domination," and "negation." In essence for the Frankfurt philosophers the critique of ideology takes the form of a philosophical-historical principle. It is the basis of their social theory. "… Social theory, …" writes Habermas, "assumes the form of a critique of ideology.".