5. Thus, in one formulation die Sache selbst is the apriori (= always already) opened-ness of the open-that-we-are, which makes possible all takings-as and attributions of "is."
a. In Heidegger's earlier terminology the apriori status of our opened-ness is called the Geworfenheit or thrown-open-ness of the Da-that-we-necessarily-are (GA 2, 74.25). Thrown-open-ness makes possible all taking-as (entwerfen). Our openness is called "thrown" because it arises from and is grounded in our groundless ("hidden", "withdrawn," relatively absential) finitude. (See no. 7, below.)
b. In Heidegger's later terminology the apriori status of our opened-ness is called the Ereignetsein or drawn-open-ness of the Lichtung-that-we-necessarily-are (Lichtung-sein: GA 69, 101.12). Our Da-sein/Lichtung-sein makes possible die Geschick des Seins, i.e., the groundless -- because grounded in our finitude -- giveness (=Geschick...) of the abiliy to understand and affirm that anything is (==...des Seins).
Glossary: Geworfenheit: throwness.
Truth will never be gathered from what is present[-at-hand] and ordinary. The disclosure [opening up] of the open and the clearing of beings happens, rather, only insofar as the approaching openness is projected within thrownness. P. 44
Ereignetsein: being enowned.
[The leap] is the enactment of projecting-open the truth of be-ing in the sense of shifting into the open, such that the thrower of the projecting-open experiences itself as thrown--i.e., as en-owned by be-ing. P. 169
Lichtung: clearing. die Geschick des Seins: the fate of beings.