In 1923 Weimar Germany lurched between economic collapse and political violence. Felix Weil, the son of the grain merchant Hermann Weil, used part of his father's fortune to found an independent Marxist research institution: on 3 February 1923 the Institut für Sozialforschung was officially opened. Not tied to the state, not aligned with a party line, but institutionally affiliated with Frankfurt University — a model unseen in Germany until then. The early years concentrated on orthodox Marxist economics and the history of the labour movement.

The turning point came in 1930 with Max Horkheimer's appointment as director. Horkheimer widened the agenda: not only economic infrastructure, but culture, family, psychology, authority, language. Theodor Adorno, Herbert Marcuse, Erich Fromm and Leo Löwenthal joined the team; Walter Benjamin was the closest external affiliate. The framework would later be called "Critical Theory": it tied Marx's critique of capitalism to Freud's analysis of the unconscious and Weber's thesis of rationalisation. The question can be reduced to a single line: when economic conditions were ripe for revolution, why did the working class choose fascism?

When the Nazis came to power in 1933 the institute was shut down; most of the staff were Jewish. By way of Geneva they relocated to New York and Columbia University. Two books written in exile stand as monuments of the theory: Adorno and Horkheimer's "Dialectic of Enlightenment" (1944) — how reason's liberating promise turned into a new form of domination; and "The Authoritarian Personality" (1950), led by Adorno — an empirical mapping of the psychological structure susceptible to fascism. In the same period the concept of the "culture industry" appeared: Hollywood, radio and popular music were now analysed not as "the people's culture" but as standardised commodity production.

Horkheimer and Adorno returned to Frankfurt in the early 1950s; the institute reopened in 1951. Marcuse stayed in America and wrote "One-Dimensional Man" (1964), a bedside book for the 1960s student movement; on the barricades of Paris and Berlin his name was spoken alongside Marx and Mao. The second generation — especially Jürgen Habermas — extended the project into a theory of communication and the democratic public sphere. The Frankfurt School lives on today as a shared language in sociology, media studies, cultural criticism and political philosophy; terms like "culture industry" are now a natural part of the critical vocabulary.