How do you justify and explain that statement? First, man is the only significance, since the universe of human subjectivity (in the end, the only universe that exists) is a reality that is beside himself, and that projects and exists precisely to the extent of projection. Secondly, the order of everything else is set in relation to that transcendence is itself, and that no other law which gives itself. It is this kind of centrality of man that identifies the existentialism with humanism. Critique of Dialectical Reason. With this work, published in 1960, the thought of Sartre begins a turn with respect to previous approaches which are reflected in Being and Nothingness. Existentialism, as had been exposed until now, suffered from a fundamental flaw that Sartre himself could see: a social, historical practice, that the very spirit of the philosopher once committed missing. In an attempt to overcome the existentialism and remove this deficiency, Sartre began a complex work of approach to Marxism, understood as a concrete philosophy of the working class and "unsurpassable horizon of our time." In the Critique of Reason dialectic, it is proposed a test of reason to want this critically reorient its way, and it coordinates from two principles: first, the assumption that Marxism is the philosophy of the present, living philosophy, second Instead, the finding that Marxism should be brought back to its condition of possibility, devoid of certain characters, particularly since its use by the Soviet Union had brought the annihilation of the individual and contempt for the particular. Thus, the task that Sartre proposed is a kind of mutual complementarity between existentialism and Marxism, although it is admitted that Marxism is the only living philosophy of our time, and existentialism as such is relegated to being an ideology to margin of Marxism (although not against it) and, therefore, an ideology "parasitic" is also true that the existentialist contribution is able to provide an anthropology and a theory of the subject of which Marxism lacks. Thus, Marxism will only become doctrine "heuristic" if you use the tools offered not only by existentialism, but also in psychoanalysis, microsociology and other sciences..