Marx’s influence during his life was not great. After his death it increased with the growth of the labor movement. Marx’s ideas and theories came to be known as Marxism, or scientific socialism, which constitutes one of the principal currents of contemporary political thought. His analysis of capitalist economy and his theories of historical materialism, the class struggle, and surplus value have become the basis of modern socialist doctrine. Of decisive importance with respect to revolutionary action are his theories on the nature of the capitalist state, the road to power, and the dictatorship of the proletariat. These doctrines, revised by most socialists after his death, were revived in the 20th century by Vladimir Ilich Lenin, who developed and applied them. They became the core of the theory and practice of Bolshevism and the Third International. Marx’s ideas, as interpreted by Lenin, continued to have influence throughout most of the 20th century. In much of the world, including Africa and South America, emerging nations were formed by leaders who claimed to represent the proletariat.

The Institute for Social Research founded in 1923 and located in Frankfurt, Germany; it brought back concern with ideology, human intentionality and reflexivity into Marxist theory and into sociology. The founders of the Frankfurt Schule thought that ideology was part of the answer and began work on the social sources of fascism and authoritarian personality. They found it in the patriarchal family; in the racism, sexism and fascism of art, cinema, magazines and other mass culture. Then too, orthodox social science tended to adopt the model of objective ‘laws’ which seemed to be beyond human reach. Radical sociology had been depoliticized by adopting a positivist style after American, French, and British Philosophy of Science. Led by Horkheimer, Adorno, Marcuse, Fromm, Benjamin and others, the Marxian interest in alienated consciousness and the creative role of humans in constructing social forms is reasserted. Critical theorists, especially Marcuse, made a criticism of the obstacles to human praxis in both capitalist and “socialist” societies. Also known as the School of Critical Theory or critical sociology, it recognizes that structural Marxism leaves many questions unanswered. Critical theory seeks to remedy this by incorporating theory from Freudianism, phenomenology, and existentialism and lately, from feminist and from postmodern scholarship

Frankfurt School comprised intellectuals, academics, and political dissidents who were ill-fitted to the contemporary socio-economic systems (capitalist, fascist, communist) of the 1930s. The Frankfurt theorists proposed that social theory was inadequate for explaining the turbulent political factionalism and reactionary politics occurring in ostensibly liberal capitalist societies in the 20th century. Critical of capitalism  and of Marxism–Leninism as philosophically inflexible systems of social organisation, the School's critical theory research indicated alternative paths to realising the social development of a society and a nation.

The Frankfurt School perspective of critical investigation (open-ended and self-critical) is based upon Freudian, Marxist and Hegelian premises of idealist philosophy. Like Karl Marx, the Frankfurt School concerned themselves with the conditions (political, economic, societal) that allow for social change realised by way of rational social institutions. The emphasis upon the critical component of social theory derived from surpassing the ideological limitations of positivism, materialism, and determinism, by returning to the critical philosophy of Kant, and his successors in German idealism — principally the philosophy of G.W.F. Hegel, which emphasised dialectic and contradiction as intellectual properties inherent to the human grasp of material reality.

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