The hypothesis of inherence gives an inadequate account of the dependence of an attribute on a substance, and is a kind of half-way house between separation and predication.
On the other hand, in the Metaphysics, the distinction between inherence and predication disappears; and what is more, the relation of an attribute to a substance is regarded as so close that an attribute is merely the substance modified.
The first difference then between the Categories and the Metaphysics is in the nature of an attribute; and the theory of inherence in the Categories is nearer to Plato and more rudimentary than the theory of predication in the Metaphysics.
In the Ontology this method is employed to determine what in reality corresponds to the empirical conceptions of substance and cause, or rather of inherence and change.
The contradictions he finds in the common-sense conception of inherence, or of "a thing with several attributes," will now become obvious.