“being” in a sense that overlaps being1 and being2. The distinction should therefore be taken as a mere schematic and heuristic tool.
Being1: being as beingness (being of beings). In fundamental ontology, as we have seen, “being” is for the most part used in the traditional (metaphysical) sense that Heidegger later refers to as the being of beings (Sein des Seienden), i.e., being insofar as it is approached (metaphysically) in terms of beings, from out of the plurality of beings. Fundamental ontology still basically understands being as meaningful presence, approached by way of its multiple instances. Beingness in this sense is nothing radically different from beings, but rather that which comprehends all beings and is common to them—beingness, that which is (to on) in beings (ta onta). It is the feature of beings by virtue of which they are.
Being2: being as the nothing. Both Parmenides and Aristotle acknowledge, in different ways, the fact that the comprehensive being of beings resists determination and definition. Only specific beings can be determined, not being itself. A reconsideration of this fact ultimately leads Heidegger to the insight that in this sense, being is, in fact, the other of beings: it is nothing in the sense of not-a-determinate-being. That which constitutes the presence of determinate instances of presence is not itself present in a determinate way. In its otherness to beings, being is the indeterminacy that allows determinacy. In his 1929 professorial lecture “What is Metaphysics?” Heidegger seeks to convey precisely this insight. The only way to think of being from within the metaphysical framework, i.e., in terms of beings, yet without determining it as a being, is to think of it as the nothing. He later paraphrases the lecture in the following way:
The nothing [Nichts] is the “not” [Nicht] of beings, and is thus being, experienced from the perspective of beings. The ontological difference is the “not” between beings and being. [. . .] That nihilating [nichtende] “not” of the nothing and this nihilating “not” of difference are indeed not all the same [einerlei], but they are the selfsame [das Selbe] in the sense of belonging together in that which abides in the being of beings. (WM, 123/PM, 97; tr. mod.)
In this second sense, being is what gives beings by differing from them in the ontological difference. However, fundamental ontology radicalizes this difference: being as the “no-thing” is no longer simple indeterminate presence as such in contrast to the determinate presence of beings, it is now the referential and contextual background of nonpresence that makes a foreground