Louis Althusser (1918–1990) was a French philosopher whose reinterpretation of Marx reshaped Marxist theory in the second half of the twentieth century. A longtime teacher at the École Normale Supérieure and a member of the French Communist Party, he sought to establish Marxism as a rigorous science rather than a humanist philosophy of history. His most influential works, produced in the 1960s, argued that Marx's mature thought represented a decisive break with the humanist, Hegelian assumptions of his early writings, a rupture Althusser described using the concept of the "epistemological break." This structuralist reading challenged both liberal individualism and the prevailing Marxist emphasis on human agency and alienation.
Althusser's political thought is most closely associated with his theory of ideology and his account of how societies reproduce themselves. He argued that ideology functions less as false consciousness than as a lived relation to the world, transmitted through what he called Ideological State Apparatuses—institutions such as schools, churches, families, and media—which operate alongside the coercive apparatuses of the state. Central to this analysis was the notion of "interpellation," the process by which ideology "hails" individuals and constitutes them as subjects. He also advanced the influential idea of "overdetermination," holding that social contradictions are shaped by multiple, uneven forces rather than reducible to a single economic cause, and he insisted on the "relative autonomy" of politics and ideology from the economic base.
These arguments made Althusser a pivotal figure in structural Marxism and left a deep imprint on subsequent theory. His emphasis on anti-humanism, on structures over subjects, and on the workings of ideology influenced students and interlocutors including Étienne Balibar, Nicos Poulantzas, and, more critically, thinkers such as Jacques Rancière and Michel Foucault. His ideas circulated widely in cultural studies, political theory, and debates about the state, hegemony, and the reproduction of power. His later career was overshadowed by mental illness and by the killing of his wife in 1980, after which he was declared unfit to stand trial and was largely withdrawn from public life. Despite the controversy surrounding his life, his conceptual vocabulary—interpellation, ideological apparatuses, overdetermination—remains a durable reference point for how scholars analyze the relationship between power, institutions, and the formation of political subjects.