This sociological critique of the ‘philosophy of praxis’ looks at the importance of the concept in the social theory of leading influential Western Marxists such as Lukács, Gramsci, Korsch, Horkheimer, Marcuse and Adorno in the inter-war period. It offers a detailed critique of Marx and Hegel, and explores the validity and implications for sociology of two of Marx’s ideas which the later theorists made the centre piece of their social theory: first, that true theory is authenticated by praxis, and second, its corollary that certain major social transformations should and would in practice render sociology redundant.