This essay explores the meaning and scope of the extended debate between Heidegger and Kant, based on his different phenomenological exercises on Kant’s theoretic and practical thought, in order to concretely develop the position for the quest on the meaning of being within the horizon of time. Heidegger’s effort finds his proper way beyond the neokantian criticism of those years and Husserl’s phenomenology, but faithful to his investigative principle of going to the things themselves. The author highlights Heidegger’s methodaccording to which any phenomenological interpretation is destruction, confrontation and radicalization in itself.