“fundament” that fundamental ontology is looking for is precisely the ontological difference (N II, 186/Ni IV, 155)—which, of course, can no longer function as a “foundation” for any traditional metaphysical foundationalism. A late marginal note to the 1964 lecture “The End of Philosophy and the Task of Thinking” makes this even more explicit: “In Being and Time, the ‘being-question’ [Seinsfrage] [is] the abbreviated title for the question concerning the provenance [Herkunft] of the ontological difference” (GA 14, 87n27).
This ambiguity explains why Heidegger felt it necessary to “correct” his earlier formulation of the ontological difference. In “On the Essence of Ground” (1929), he speaks of ontical and ontological truth, which concern beings in their being and the being of beings, respectively, and belong together on the basis of their relation to the ontological difference. The essence of truth in general is thus necessarily “forked” (gegabelt) in terms of the ontical and the ontological and is possible only on the basis of this distinction (WM, 134/PM, 105–06). In a later marginal note, Heidegger comments:
Here the essence of truth is conceived as “forked” in terms of the “distinction between” [Unterschied] as a fixed reference point, instead of the contrary approach of overcoming the “distinction” in terms of the essence of the truth of beyng [Seyns], or of first thinking the “distinction” as beyng itself and therein the beyngs of beyng [das Seyende des Seyns]—no longer as the being [Sein] of beings. (WM, 134n[c]/PM, 105n[c]; tr. mod.)
The “beyngs” (das Seyende) in the event of beyng as differentiation (being3) can be understood as an idiosyncratic designation for the meaningful presence of beings (being1) insofar as it is understood in terms of its differentiation from its temporally contextual background (being2), with which it nevertheless belongs together in an ecstatic unity of complicated presence. Distinguishing these aspects of being also renders comprehensible a striking textual alteration, in the fifth edition of What is Metaphysics? (1949), to “Postscript to ‘What is Metaphysics?’” which was originally appended to the text in the fourth edition (1943). In 1943 the text reads: “[. . .] the truth of being entails that being indeed [wohl] abides [west] without beings, but a being is never without being.” In 1949, however, Heidegger writes: “[. . .] the truth of being entails that being never [nie] abides without beings, that a being [ein Seiendes] never is without being [Sein]” (WM, 306/PM, 233, 374; tr. mod.).