In the Corpus Aristotelicum there are two different theories of substance which apply to the sublunary world. The first theory is found in the Categories and selects the individual concrete as a primary substance (πρώτη oὐσία). The second is found in the Metaphysics (mainly in book Z) and selects the Form (εἶδος) and the Essence (τὸ τί ἦν εἶναι) as a primary substance. Most of the interpretations of modern Aristotelian scholarship claim an inconsistency. They suggest that if at all Aristotle has a theory of substance, then it is either the substance theory of the Categories or the one of the Metaphysics but not both of them. The supposition of all these interpretations is that Aristotle’s theory of substance is unambiguous and that there can be only a single primary substance. These interpretations suppose that the theory of substance is applicable only to a single domain, namely to ontology.In my paper I argue that this supposition is false. I suggest that Aristotle’s theory of substance is applicable not only to ontology but also to the domain of determinology whose meaning is explained in the paper. The theory of substance of the Categories applies to ontology whereas the one of the Metaphysics applies to determinology. The two theories are consistent with each other in a way that there are two commensurate sorts of primary substance: the individual concrete as the ontological primary substance of the Categories and the Form‑Essence as the determinative primary substance of the Metaphysics.Furthermore, I claim that Aristotle’s concept of substance is manifold and flexible. The concept evolves and is expanded in the Metaphysics. It is manifold because his theory of substance has a certain structure which includes the following three criteria for selecting a primary substance: (1) subjecthood viz. being a subject (τὸ ὑποκείμενον), (2) independence (τὸ χωριστόν) and (3) (well) determined individuality (τὸ τόδε τι). Aristotle’s concept of substance is flexible because these criteria do not have an absolute signification per se but are general and relative. They get a final signification when they are applied either to the ontology in the Categories or to the determinology in the Metaphysics. Their application to a certain domain establishes a theory of substance according to the domain in question and selects a primary substance according to the same domain. Aristotle’s concept of substance is flexible also because in the Metaphysics he enlarges his first concept of substance expressed by the three criteria by adding a new sort of substancehood expressed by the idion criterion.

History of Philosophy | Philosophy and Religion