The research focuses on the problem of interpretation of such a concept as the origin, which is ultimate for philosophical thought and bases existentially oriented constructions of Franz Rosenzweig and Martin Heidegger. It is argues in this paper the fundamental difference between the interpretations of the origin in “The Star of Redemption» and in «Being and Time”, despite all points of intersection and coincidences that bring closer together dialogical and existential-historical thinking. Such differentiation of positions is determined by the necessity (...) both to neutralize romantic connotations, which expose the origin ( Ursprung ) as abyss ( Abgrund ), and to methodologically clarify the possibility not so much to think as to practically assert a limited and unclosed within itself integral being, including ontological and ethical dimensions. The origin of oblivion and renewal, imposed by Heidegger’s hermeneutics of facticity, is contrasted with Rosenzweig's origin of the “eternal overworld”, reconstructed on the basis of Herman Cohen's religio-philosophical intuitions and his analysis of the infinitesimal as a principle of reality. Rosenzweig’s position, which aims at a correlative consideration of the purely logical content of the infinitesimal quantity (almost-Nothing) and the existential experience of the finiteness of everything, is favorably distinguished by the absence of a one-sided focus on recalling, where fore-running although is declared, but it is immediately restrained by being-towards-death. As a result, Rosenzweig’s dialogism turns out to be free from overestimating what Heidegger’s interpretation calls resoluteness, which in fact is not much different from paralysis in the clearance of being. Cohen’s problem of an infinite task's realization, being actualized in Rosenzweig’s conception, allows to go beyond being-towards-death in juxtaposing the trajectories of initial elements into a true gestalt. (shrink)