This was what was involved in the first step into philosophy. For right here from the very beginning, in Heidegger's view, was the failure of the Greeks in general, and for that matter of all subsequent metaphysics, to take into account "the not" (das Nicht) between things (Seinde) and being (Sein). This represents the failure to note what Heidegger calls the "ontological difference." This is the beginning of metaphysics. Here also begins the forgetting of being. As Heidegger says in his Nietzsche volumes, inasmuch as metaphysics thinks things from within their being, it fails to think being as being (Sein als Sein).

This note of the "ontological difference" is not something absolutely new in the thought of Heidegger. It had already been struck, although very lightly, in Sein und Zeit with the distinction between the ontological (ontologisch) and the merely ontic (ontisch) and the related distinction between authenticity (Eigentlichkeit) and inauthenticity (uneigentlichkeit). The note of the distinction was struck a little more lightly in Sein und Zeit because the ontological or the authentic always came from out of the ontic and the inauthentic. Thus Heidegger speaks of a preontological understanding of being. He also notes that it is from "the they" (das Man) that Dasein gains this preontological interpretation of his being.

¶ 7:12 PM