theology, ontology, and metaphysics.
In a theistic or non-dual metaphysics, theology overlaps almost entirely with ontology and metaphysics.
If God is being itself, ground of being, or all that is, then theology becomes ontology at its highest level. If God is the source, principle, or structure of reality, theology becomes metaphysics.
The separation between theology and philosophy is historically contingent, largely post-medieval, and often artificial. In Neoplatonism, Kabbalah, Hermeticism, Vedanta, and ACIM, theology is simply metaphysics spoken in symbolic or devotional language.
the relationship between ontology and metaphysics.
Ontology and metaphysics bleed into one another, especially outside modern analytic philosophy.
Historically, ontology was treated as a subdivision of metaphysics. In Aristotle, “first philosophy” covered both being qua being and first causes. The later separation is a methodological convenience, not an absolute division.
A useful distinction is this. Ontology asks what is. Metaphysics asks what it is like and why it is so.
Ontology names being. Metaphysics explains structure, causality, principle, and ground.
If being is reality, then ontology and metaphysics converge. If reality is illusion, simulation, or mental projection, then ontology still asks what exists (illusion, simulation, mind), while metaphysics asks how that appearance is generated and sustained.
So even when reality is declared illusory, ontology does not disappear. It simply relocates what counts as real.