Metaphysical thinking is determined by the difference between Being and
beings. The way in which metaphysics has thought the relation of Being
and beings has given it the structure of both ontology and theology,
regardless of whether it has made explicit use of these terms or not.
Metaphysics is ontology in that it thinks Being as the first and most
universal ground common to all beings. Metaphysics is theology in that
it thinks Being as the highest ground above all beings, ultimately as
the ground of itself, /causa sui, /which is the metaphysical concept of
God. Metaphysics is thus in its very nature onto-theo-logic.
Joan Stambaugh in MARTIN HEIDEGGER, IDENTITY AND DIFFERENCE, 14