Most Buddhists understand that modern philosophy has never answered the question of what is reality? Modern philosophy doesn’t know how the really real or true reality is to be known or what exactly will be known when it does know (if it ever does!). This is a problem of epistemology. It attempts to answer the question, “What is knowing and the known?”
If we assume that ontology is the science of what is ultimately real, it strikes me odd that much of it appears to be conditioned by epistemology and its confusion. One such problem, for example, is how is our knowledge of true reality to be derived? Is it acquired through pure intellection, concepts, sensory consciousness or what we Buddhist call the Five Aggregates? For me this is crucial because if this is the way we approach ontology, by way of epistemology, we are not even close to what Buddhist ontology should be, which should not rely on epistemology.
If a Buddhist ontology is to know or to be directly acquainted with true reality (which has a variety of names in Buddhism such as pure Mind and Buddha-nature) it is not an easy task. To be sure, we cannot do it by way of our intellect, imagination or by means of concepts which leads us back to epistemology with all of its unresolved problems. We can't walk on an epistemological path, in other words, and expect to get to the ontologic Land of Jewels.
Thus we are thrown back on introspection (dhyana) as a proper means of apprehending true reality which is not at all epistemological. By means of introspection we are inwardly seeking true reality, or if you prefer, Buddha Mind, without any epistemological aids such as pure intellection. In this wise, introspection opens up before the immediacy of true reality, of which we are intrinsically, but which, as yet, remains unmediated by us. The strength and depth of introspection, that it should reach ultimate reality, which will then recognize itself, depends on itself, not on epistemology.
This for me is what Buddhist ontology should be about. It's an ontology free of epistemology which relies, instead, on profound introspection. It requires of us that our journey should deepen introspection such that we are, eventually, able to penetrate through the veil of phenomena and come into direct, non-conceptual contact, with ultimate reality.