Heidegger on God's Existence

I was reading through the "Letter on Humanism" and found this interesting quote. The context is Heidegger's discussion of man's being as being-in-the-world and its consequences.

With the existential determination of the essence of man, therefore, nothing is decided about the "existence of God" or his "non-being," no more than about the possibility of gods. Thus it is not only rash but also an error in procedure to maintain that the interpretation of the essence of man from the relation of his essence to the truth of Being is atheism. And what is more, this arbitrary classification betrays a lack of careful reading. No one bothers to notice that in my essay "On the Essence of Ground" the following appears: "Through the ontological interpretation of Dasein as being-in-the-world no decision, whether positive or negative, is made concerning a possible being toward God. It is, however, the case that through an illumination of transcendence we first achieve an adequate concept of Dasein, with respect to which it can now be asked how the relationship of Dasein to God is ontologically ordered." If we think about this remark too quickly, as is usually the case, we will declare that such a philosophy does not decide either for or against the existence of god. It remains stalled in indifference. Thus it is unconcerned with the religious question. Such indifferentism ultimately falls prey to nihilism.

But does the foregoing observation teach indifferentism? Why then are particular words in the note italicized--and not just random ones? For no other reason than to indicate that the thinking that thinks from the question concerning the truth of Being questions more primordially than metaphysics can. Only from the truth of Being can the essence of the holy be thought. Only from the essence of the holy is the essence of the divine to be thought. Only in the light of the essence of divinity can it be thought or said what the word "God" is to signify. Or should we not first be able to hear and understand all these words carefully if we are to be permitted as men, that is, as ek-sistent creatures, to experience a relation of God to man? How can man at the present stage of world history ask at all seriously and rigorously whether the god nears or withdraws, when he has above all neglected to think into the dimension in which alone that question can be asked? But this is the dimension of the holy, which indeed remains closed as a dimension if the open region of Being is not cleared and in its clearing is near man. Perhaps what is distinctive about this world-epoch consists in the closure of the dimension of the hale [des Heilen]. Perhaps that is the sole malignancy [Unheil].
"Letter on Humanism," in Martin Heidegger: Basic Writings (New York: HarperCollins, 1993), 253-254.

Heidegger's thought is not essentially atheistic, whatever his own religious leanings. However, his thought does elucidate the very grounds on which we can think of the divine: in terms of man's understanding, his being, which must be a factor in the God-man relationship. If we misunderstand man's essential nature then we will also misunderstand his relationship to the divine (as we will his relationship to everything else). Indeed, how can we seriously question the existence of God (whether he "nears or withdraws") when we ignore the very grounds on which that question rests, the very grounds on which such questioning is possible--man's essential relationship with being?

But man's distinctive feature lies in this, that he, as the being who thinks, is open to Being, face to face with Being; thus man remains referred to Being and so answers to it. Man is essentially this relationship of responding to Being, and he is only this. This "only" does not mean a limitation, but rather an excess.
"The Principle of Identity," Identity and Difference, Joan Stambaugh, trans. (New York: University of Chicago Press, 1969), 31.

Such thinking, in the wake of Heidegger's philosophy, has begun in the works of Emmanuel Levinas, Jean-Luc Marion, John Caputo, and Adriaan Peperzak. As with Heidegger's later work on ontology itself, the answer seems to lie in that which is 'beyond being.'