“We assert now that Being is the proper and sole theme of philosophy. This is not our own invention; it is a way of putting the theme which comes to life at the beginning of philosophy in antiquity, and it assumes its most grandiose form in Hegel's logic. At present we are merely asserting that Being is the proper and sole theme of philosophy. Negatively, this means that philosophy is not a science of beings but of Being or, as the Greek expression goes, ontology. We take this expression in the widest possible sense and not in the narrower one it has, say, in Scholasticism or in modern philosophy in Descartes and Leibniz.

A discussion of the basic problems of phenomenology then is tantamount to providing fundamental substantiation for this assertion that philosophy is the science of Being and establishing how it is such. The discussion should show the possibility and necessity of the absolute science of Being and demonstrate its character in the very process of the inquiry. Philosophy is the theoretical conceptual interpretation of Being, of Being's structure and its possibilities. Philosophy is ontological."

―from_The Basic Problems of Phenomenology_”