Averroes and Aquinas on the Primary Substantiality of Form

Does Aristotle change his mind on what primary substance is when he moves from the "Categories" to the "Metaphysics"? This question summarizes the debate among contemporary interpreters of Aristotle about the relation between the ontology of the "Metaphysics" and that of the "Categories". The so-called “Compatibilism vs. Incompatibilism Problem”is of course not a fresh question. From Late Antiquity onward commentators have addressed this issue. In recent years, however, it has been charged with new philosophical significance,to the point that, depending on the answer one gives to it, different forms of Aristotelian philosophy result. Over the last years, Gabriele Galluzzo pointed out that in the Middle Ages two leading interpreters such as Averroes and Thomas Aquinas proposed different understandings of Aristotle's doctrine of primary substance, incompatibilist the former and compatibilist the latter. In this essay I call into question this thesis. My point is that, while differing from each other in the emphasis they put on the substantiality of (substantial) form, Averroes and Aquinas share the compatibilist claim. I provide arguments, both textual and philosophical, for proving this point.