In this paper we seek to show that Heidegger’s transcendantal thought of the years 1925-30 absolutizes contingent categories. In this way, the point to be understood is that the Dasein is constituted by an ontological receptivity which assigns him to every modality of his structure. To the extent that Heidegger assumes the kantian and later husserlian project of an a priori analysis of man and of his phenomenological structure, he is led to a philosophy that immobilizes man in a network of permanent modalities of existentiality, and refuses the least transformation that would come from a natural evolution or from a praxis. We show that this immobility of the Dasein’s constitution can be found in his self-refering and reticular structure, and also in the way that it is a powerlessness (finitude) that determinates the possibility of an undertanding of Being.