In this paper I argue that the central issue in Heidegger’s path of thought from Being and Time to Contributions and beyond is what he will later call “the matter itself”: neither the meaning of being nor the analysis of Dasein but a transformational encounter in the margins of fundamental ontology. Heidegger’s account of temporality and transcendence from the late 1920s is a clue to the transformation, but it is not until the completion of fundamental ontology in the naming of (...) ontological difference that he arrives at a crisis which performs the transformation and announces the “overturning.” This interpretation revolves around a reading of Heidegger’s 1929 treatise “On the Essence of Ground” in which the text and subsequent marginal notes prepare the transition from Being and Time to Contributions, from Sein to Seyn, and from ontological difference to its appropriation. Thus we find that the language of Ereignis beginning in the 1930s and whatever we might call the “turn” signal the doing of justice to the original task from Being and Time. (shrink)