Aristotle knew of this tradition when he began his "Metaphysics", and had already drawn his own conclusion, which he presented under the guise of asking what being is:"And indeed the question which was raised of old is raised now and always, and is always the subject of doubt, viz., what being is, is just the question, what is substance? For it is this that some assert to be one, others more than one, and that some assert to be limited in number, others unlimited. And so we also must consider chiefly and primarily and almost exclusively what that is which is in this sense."