His eclecticism, his ontology and his philosophy of history were declared in principle and in most of their salient details in the Fragmens philosophiques (Paris, 1826).
It would be surprising if a new ontology yielded a testable hypothesis.
We, on the contrary, mainly through the influence of Descartes, rather ask what are the things we know, and therefore, some more and some less, come to connect ontology with epistemology, and in consequence come to treat metaphysics in relation to psychology and logic, from which epistemology is an offshoot.
They become in practice Psychology, Ontology and Eclecticism in history.
It would seem, then, that Academic scepticism began with those who had been reared by Plato himself, having its origin in their acceptance of the scientific element of his teaching apart from the ontology which had been its basis.
Valid for all intelligences, ontology must furnish us with a clue.
These would embrace, according to the Wolffian scheme long current in philosophical textbooks, ontology proper, or the science of being as such, with its three-branch sciences of (rational) psychology, cosmology and (rational or natural) theology, dealing with the three chief forms of being - the soul, the world and God.
This is the basis and the only proper basis of ontology or metaphysics - the science of being - and of the philosophy of history.
In his ontology Xenocrates built upon Plato's foundations: that is to say, with Plato he postulated ideas or numbers to be the causes of nature's organic products, and derived these ideas or numbers from unity (which is active) and plurality (which is passive).
When they, the immediate successors of Plato, rejected their master's ontology and proposed to themselves as ends mere classificatory sciences which with him had been means, they bartered their hope of philosophic certainty for the tentative and provisional results of scientific experience.