 An original way of distinguishing between ontology and metaphysics underlies the third stage of theoretical development. Ontology, for Hartmann, deals with what can be subsumed under at least partially cognizable categories, while metaphysics deals with the nonrational or noncognizable. Two main consequences follow from this view of ontology: firstly, ontology is primarily a theory of categories, in the sense that all ontological distinctions have the form of categories (AIntro1), and secondly, “science” in all its branches (including the human/social sciences) is ontological in all its ramifications (OLF37a), and is the most powerful ally of ontology. This is rather at odds with the mainstream view of science as an eminently epistemological affair (present in positivism, Neo-Kantianism, phenomenology, existentialism, postmodernism, etc.). This is one of the issues on which Hartmann firmly departs from the Neo-Kantian legacy, as well as from the generalized critique of the natural scientific approach in mainstream twentieth century Continental philosophy.