Translated by Pete Ferreira
However, as with the confrontation with Aristotle, the confrontation with Kant will also arrive at the critical conclusion that Kant's attempt to determine the ontological structure of subjectivity is not set in a sufficiently radical manner; that is, remaining substantially within the Cartesian horizon of a dichotomous understanding of being that separates thought and extension, and remaining in the end bound to a naturalistic understanding of time, Kant would not arrive at determining in a radical manner what is the unitary ontological structure on which rests the theoretical determinations and practical determinations of the subject.79
This task of determining the ontological unity of human life, precisely as originary temporality, is taken up and addressed explicitly by Heidegger in the analytic of existence, on which rests his metaphysics of finitude.
We can say then that the fundamental outcome of the confrontation with Aristotle (and then with Kant) arrives at, is the systematic development, radicalization and solution of the problem from which Heidegger had made his move in the horizon of Husserlian phenomenology, that is, the problem of the ontological determination of the way of being of human life. Seizing the structure of the finite being in its character as being discovering (truth), having-been and temporality, Heidegger thinks with those he has the Archimedean point on the basis of which he can pursue radically the basic intentions which from the beginning had inspired his confrontation with tradition, and thus, through the de(con)struction of traditional ontology, to that metaphysics of being-there or basic ontology that he presents in Being and Time (and whose project he continues to work on until the end of the 1920s).
79 See GA 25, 207. On Heidegger's appropriation of Kant and the critique of the Kantian determination of the subject see I. Görland, Transzendenz und Selbst. Eine Phase in Heideggers Denken, Klostermann, Frankfurt a. M. 1981, and also my Soggettività e temporalità: considerazioni sull’interpretazione heideggeriana di Kant alla luce delle lezioni di Marburgo (see footnote 53).