What is onto-theology (Heideggerian)?

Question

From what I understand, it is a term that combines ontology and theology, at least in the case of Heidegger, to describe modern metaphysics. To understand what onto-theology is, I first tried to understand the other two fields of study which are ontology and theology. To put it very basically, the former is the study of being/existence (lowest/basic) while the latter is the study of God (highest/supreme).

However, what do these two seemingly polar fields have in common that they can be combined? And subsequently, what did Heidegger see in modern metaphysics that allowed him to say that "metaphysics is onto-theology"?

Answer 1

1. It's (probably) important to realise that Heidegger doesn't coin the term "ontotheology." He gets it from Kant, notably in the Lectures on "philosophical theology" where he considers the term as designating that part of theology which "considers God merely in terms of concepts" (Cornell edition, p. 4).

2. Nevertheless, Heidegger makes some fairly bold claims on behalf of a relationship between ontology and theology:

   Western metaphysics... since its beginning with the Greeks has eminently been both ontology and theology, still without being tied to these rubrics. ("The Onto-theo-logical Constitution of Metaphysics", p. 54).

   While this claim seems grandiose, its worth remembering that this connection is made in Aristotle's Metaphysics XI:

   Since there is a science of Being qua Being and separately ["ontology"], we must inquire whether this should be regarded as identical with natural science or if it should be regarded as a distinct branch of knowledge. Physics deals with things which contain a source of motion in themselves, and mathematics is speculative and is a science which deals with permanent things, but not with things which can exist separately. Hence there is a science distinct from both of these, which deals with that which exists separately and is immovable... And if there is an entity of this kind in the world of reality, here surely must be the Divine, and this must be the first and most fundamental principle. (Armstrong translation, 1064a29–36)

   Aristotle then goes on to explicitly name this third science "theology" and claim that it is "the highest" of the speculative sciences.

3. So when Heidegger says "metaphysics is onto-theo-logy," he's not trying to make a claim about metaphysics; rather he's trying to draw our attention to the way that metaphysics characterises itself, and in a way to provoke the very question you've asked: how have the two things seem to become so intertwined or, as he writes:

   The onto-theological character of metaphysics has become questionable for thinking... from the experience of a thinking which has discerned in onto-theo-logy the still unthought unity of the essential nature of metaphysics.

   ...

   It would be rash to assert that metaphysics is theology because it is ontology. One would say first: Metaphysics is theology, a statement about God, because the deity enters into philosophy. Thus the question about the onto-theological character of metaphysics is sharpened to the question: How does the deity enter into philosophy...? ("The Onto-theo-logical Constitution of Metaphysics", p. 55)

   The important point is that its not that there was something called ontology which became intertwined with something called theology and produced a third thing called metaphysics. Its rather a complete reverse of this: metaphysics has always left unthought the identity between ontology and theology that has been implicit in it. Its only now, at the end of a process that separates something we call "ontology" from something we call "theology" that the relationship between them comes into question at all.

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4. Heidegger's questioning of "onto-theology" is bound up with the project he announces in Being and Time as the "destruction" of the traditional content of ontology. The problem is that continuing to use onto-theological language after the point where the question of the relation between being and God has emerged tends to impoverish both of those terms, so that, on the one hand, God comes to be thought as a kind of being among others and, on the other, being comes to be thought as ordered towards God as what is the highest form of being.

   For Heidegger, metaphysics, by continuing to develop onto-theologically, leaves the being of beings unexamined, and so being comes to be determined by something other than being. God, too, fares no better, since God is unable to be understood as divine---in the sense that Aristotle and Plato use this word---but only as one being amongst others. These dual aspects of the impoverishment of being and of god, Heidegger associates with the thesis of God as causa sui, which allows him to say:

   [Causa sui] is the right name for the god of philosophy. Man can neither pray nor sacrifice to this god. Before the causa sui, man can neither fall to his knees in aw nor can he play music and dance before this god.

   The god-less thinking which must abandon the god of philosophy, god as causa sui, is thus perhaps closer to the divine God. ("The Onto-theo-logical Constitution of Metaphysics", p. 72)

   By bringing onto-theology into question, Heidegger hopes to open up a different way of thinking about beings and a different way of relating to the divine.