Abstract
The paper studies, within the framework of Martin Heidegger's narrative of the history of metaphysics, two perspectives on the unity of being: the "protometaphysical" perspective of Parmenides, the thinker of the "first beginning" of Western philosophy, and the postmetaphysical perspective of Heidegger, situated in the ongoing transition from the Hegelian and Nietzschean end of metaphysics to a forthcoming "other beginning" of Western thought. Both perspectives involve a certain "crisis", in the literal sense of the Greek krisis, "distinction," "decision." Parmenides' goddess exhorts the thinker to decide for being in the sense of pure intelligible accessibility or presence and to exclude all references to non-accessibility and non-presence. This is the foundation of the Parmenidean thesis of the unity of being. In the Heideggerian perspective, by contrast, meaningful presence is seen as constituted precisely by references to a withdrawing meaning-context, to background dimensions that in themselves are not immediately present. Since presence is constituted only in terms of non-presence, the "decision" or "crisis" between presence and non-presence is an unresolvable and irreducible feature of postmetaphysical thinking.