§32. Continuation: The idea of first philosophy in Aristotle.
a) First philosophy as ontology (ὂν ᾗ ὄν) and as theology. Explication of this duality on the basis of the Greek understanding of Being (= presence).
Following Aristotle, we have gained some clarity concerning the question of ὄν, insofar as we can say it does not deal with a definite region of objects but with τὰ πάντα, with ὂν ᾗ ὄν, with the ὅλον. The question concerns the determinations which constitute beings in their Being. This idea of first philosophy, as Aristotle calls it, the original science of beings, is for him intersected by another fundamental science, which he designates as θεολογική, so that we have:
πρώτη φιλοσοφία
θεολογική
the science that considers ὂν ᾗ ὄν.
This latter came to be called "ontology. " Aristotle himself does not ever use the term. For the science which considers ὂν ᾗ ὄν, Aristotle uses the expression πρώτη φιλοσοφία. Thus theology as well as ontology claim to be πρώτη φιλοσοφία.
This duality can be pursued further, into the Middle Ages up to the ontology of the modern period. People have sought to mediate between ontology and theology in Aristotle, in order to gain a "well-rounded picture" of Aristotle. This way is not fertile for an understanding of the matters at issue. Instead, the question should be raised why Greek science traveled such a path that it landed, as it were, with these two basic sciences, ontology and theology. Theology has the task of clarifying beings as a whole, the ὅλον, the beings of the world, nature, the heavens, and everything under them, to speak quite roughly, in their origins, in that by which they properly are.1 It must be noted that the clarification of beings as a whole, nature, by means of an unmoved mover has nothing to do with proving God through a causal argument. Theology has the whole, the ὅλον, as its theme, and ontology too has the whole as its theme and considers its ἀρχαί. Both, theology and ontology, take their departure from beings as whole, as ὅλον; and it is their concern to understand the ὅλον, the whole in its entirety, as being. Why did Greek science and philosophy arrive at these two basic sciences? (In Plato they are still wholly intermingled; he leaves them even more unclarified than Aristotle does. But in fact he already moves in both these dimensions.)
1. In the comments which follow, Heidegger takes his orientation from Met. XII, I, 1069a18ff.