My aim in this paper is to examine Aristotle’s notions of priority in order to determine which sort of priority he ascribes to substances. I try to show that we cannot accept the traditional idea that a substance’s priority must be understood as existential independence. Aristotle rather ascribes to substances a priority in terms of completion, as he ascribes to substances-of-something some specific sort of causal-explanatory priority. Besides that, Aristotle argues, against Platonism, that these two sorts of priority (completion priority and causal-explanatory priority) must be kept apart from each other in any successful ontology.
