Take a swim at Tiber River . This programme has been adopted with little variation by most Catholic philosophers. Ontology is a fundamental interpretation of the ultimate constituents of the world of experience. Ontology is therefore the fundamental science since it studies the basal constituents and the principles presupposed by the special sciences. All the other parts of philosophy, cosmology, psychology, theodicy, ethics, even logic, rest on the foundation laid by ontology.
Ontology is accused of dealing with the merely abstract.
But all science is of the abstract, the universal, not of the concrete and individual. It is idle to say that of these ultimate abstractions we can have no distinct knowledge. The very negation of their knowableness shows that the mind has some knowledge of that which it attempts to deny. Ontology simply endeavours to make that rudimentary knowledge more distinct and complete. It was Aristotle who first constructed a well-defined and developed ontology.