Although Marxism appeared in the mid-nineteenth century, when the contradictions inherent in capitalist society became acutely apparent in the advanced countries of Europe and its future gravedigger and creator of the new communist society, the working class, entered the historical arena, Marxist thought remains relevant in this newly-started twenty-first century. Marxist theory (later converted into Marxist-Leninist) represented a true resolution in the history of human thought, providing answers to the problems posed by the development of society. The originality of the work of Marx and Engels must be sought in the political field and not in the economic or philosophical one. They were the first to discover the historical potential of the new class that capitalism had created, the modern proletariat, a class that could achieve universal liberation from all existing forms of oppression and exploitation. In itself, the decisive contribution made by the founders of historical materialism was the theory of the proletarian revolution, which was concretized in the October Revolution (1917) in Russia. This work raises how in their writings there is an apparent contradiction: their belief that under capitalism the revolutionary consciousness of the proletariat would develop in a relatively rectilinear way, and their assertions that the fetishistic nature of social-capitalist relations gives rise to forms of ideological mystification, which notably conceal the basic features of the capitalist mode of production. However, although Marx did not foresee the difficulties of the transformation of revolutionary consciousness into a revolutionary form, seeing it as a relatively rectilinear process, his intellectual legacy is extremely fruitful and remains relevant in this current neoliberal atmosphere, which seeks to make us forget that there have been great revolutions.