It is the essence of a work such as Marx's to provoke new interpretations in the course of history. His work is, in fact, at once thought, and an action aimed at transforming the human and social world. The sudden appearance of a communist world, in historically unforeseen forms, its coexistence with a capitalist world—itself quite different from its 19th century version—and the relationship between developed countries and those developing countries which were once colonies; this present state on our planet leads to new inquiries about Marxism and to a return to Marx's fundamental writings and texts, which are inseparable from Lenin's interpretations. Any reading and interpretation of Marx in a contemporary historical context is due, today, to Louis Althusser and his pupils. We are not, however, going to dwell on this actual (still unforeseable) meaning, but on some of the major themes of this interpretation. What is the “scientific,” what is this new science, historical materialism, that Marx had begun to form? what, in this light, becomes of philosophy, that is, with Marx and Lenin, dialectical materialism? and lastly what sort of relation is there between the ideologies, in a sense of which Marx is the instigator, and science or philosophy?