"Hypokeimenon is a term in metaphysics which loosely means the "underlying thing" or the substratum. To search for the hypokeimenon is to search for that substance which persists in a thing going through change—its essential being. It is conceptually similar to Spinoza's "substance" and Kant's concept of the noumenon in The Critique of Pure Reason."
I believe few people would say such a thing does not exist. Yet, is this not God?
Is not God the hypokeimenon of the universe, however imprecisely it is defined?