The Frankfurt School is a school of neo-Marxist social theory, social research, and philosophy. The grouping emerged at the Institute for Social Research (Institut für Sozialforschung) of the University of Frankfurt am Main in Germany when Max Horkheimer became the Institute's director in 1930. The term "Frankfurt School" is an informal term used to designate the thinkers affiliated with the Institute for Social Research or influenced by them: it is not the title of any institution, and the main thinkers of the Frankfurt School did not use the term to describe themselves.

The Frankfurt School gathered together dissident Marxists, severe critics of capitalism who believed that some of Marx's alleged followers had come to parrot a narrow selection of Marx's ideas, usually in defense of orthodox Communist or Social-Democratic parties. Influenced especially by the failure of working-class revolutions in Western Europe after World War I and by the rise of Nazism in an economically, technologically, and culturally advanced nation (Germany), they took up the task of choosing what parts of Marx's thought might serve to clarify social conditions which Marx himself had never seen. They drew on other schools of thought to fill in Marx's perceived omissions. Max Weber exerted a major influence, as did Sigmund Freud (as in Herbert Marcuse's Freudo-Marxist synthesis in the 1954 work Eros and Civilization). Their emphasis on the "critical" component of theory was derived significantly from their attempt to overcome the limits of positivism, crude materialism, and phenomenology by returning to Kant's critical philosophy and its successors in German idealism, principally Hegel's philosophy, with its emphasis on negation and contradiction as inherent properties of reality. A key influence also came from the publication in the 1930s of Marx's Economic-Philosophical Manuscripts and The German Ideology, which showed the continuity with Hegelianism that underlay Marx's thought: Marcuse was one of the first to articulate the theoretical significance of these texts.

The intellectual influences on and theoretical focus of the first generation of Frankfurt School critical theorists appear in the following diagram:



The Institute made major contributions in two areas relating to the possibility of rational human subjects, i.e. individuals who could act rationally to take charge of their own society and their own history. The first consisted of social phenomena previously considered in Marxism as part of the "superstructure" or as ideology: personality, family and authority structures (its first book publication bore the title Studies of Authority and the Family), and the realm of aesthetics and mass culture. Studies saw a common concern here in the ability of capitalism to destroy the preconditions of critical, revolutionary consciousness. This meant arriving at a sophisticated awareness of the depth dimension in which social oppression sustains itself. It also meant the beginning of critical theory's recognition of ideology as part of the foundations of social structure. The Institute and various collaborators had a gigantic effect on (especially American) social science through their work The Authoritarian Personality, which conducted extensive empirical research, using sociological and psychoanalytic categories, in order to characterize the forces that led individuals to affiliate with or support fascist movements or parties. The study found the assertion of universals, or even truth, to be a hallmark of fascism; by calling into question any notion of a higher ideal, or a shared mission for humanity, The Authoritarian Personality contributed greatly to the emergence of the counterculture.

The nature of Marxism itself formed the second focus of the Institute, and in this context the concept of critical theory originated. The term served several purposes - first, it contrasted from traditional notions of theory, which were largely either positivist or scientific. Second, the term allowed them to escape the politically charged label of "Marxism." Third, it explicitly linked them with the "critical philosophy" of Immanuel Kant, where the term "critique" meant philosophical reflection on the limits of claims made for certain kinds of knowledge and a direct connection between such critique and the emphasis on moral autonomy. In an intellectual context defined by dogmatic positivism and scientism on the one hand and dogmatic "scientific socialism" on the other, critical theory meant to rehabilitate through such a philosophically critical approach an orientation toward revolutionary agency, or at least its possibility, at a time when it seemed in decline.

Finally, in the context of both Marxist-Leninist and Social-Democratic orthodoxy, which emphasized Marxism as a new kind of positive science, they were linking up with the implicit epistemology of Karl Marx's work, which presented itself as critique, as in Marx's "Capital: a critique of political economy", wanting to emphasize that Marx was attempting to create a new kind of critical analysis oriented toward the unity of theory and revolutionary practice rather than a new kind of positive science. In the 1960s, Jürgen Habermas raised the epistemological discussion to a new level in his "Knowledge and Human Interests" (1968), by identifying critical knowledge as based on principles that differentiated it either from the natural sciences or the humanities, through its orientation to self-reflection and emancipation.

Although Horkheimer's distinction between traditional and critical theory in one sense merely repeated Marx's dictum that philosophers have always interpreted the world and the point is to change it, the Institute, in its critique of ideology, took on such philosophical currents as positivism, phenomenology, existentialism, and pragmatism, with an implied critique of contemporary Marxism, which had turned dialectics into an alternate science or metaphysics. The Institute attempted to reformulate dialectics as a concrete method, continually aware of the specific social roots of thought and of the specific constellation of forces that affected the possibility of liberation. Accordingly, critical theory rejected the materialist metaphysics of orthodox Marxism. For Horkheimer and his associates, materialism meant the orientation of theory towards practice and towards the fulfillment of human needs, not a metaphysical statement about the nature of reality.