Abstract
Michael Wedin’s Aristotle’s Theory of Substance provides an interpretation of primary substance in Metaphysics Book Z that is compatible with the ontology of the Categories. The incompatibilist position holds that primary substance in the Categories is the concrete, individual substance, like Socrates, whereas the title of primary substance in Metaphysics Z goes to the eidos, the form or the species. Hence, the ontology of the Categories is incompatible with the ontology of Metaphysics Z. One compatibilist strategy argues that the c-substance remains primary substance in Metaphysics Z. Wedin takes another tack. He argues that c-substances are ontologically primary in both texts, and that Metaphysics Z introduces a new kind of priority, explanatory priority, awarded to the form of c-substances. Since c-substances and their forms are prior in different senses, the incompatibility vanishes. Wedin’s claim is stronger than mere compatibilism, however, since what forms explain are basic features of c-substances. Hence, Metaphysics Z is not only compatible with the Categories, “it is a theory about the theory of the Categories”. Wedin argues for what I call strong compatibilism.