Lo statuto della differenza specifica: da Alessandro di Afrodisia a Giamblico

This article focuses on the debate concerning the status of specific differentiae from Alexander of Aphrodisias to Iamblichus. First, I outline Alexander’s views on the substantial status of differentiae and his distinction between the differentia insofar as it is taken in isolation and the differentia insofar as it is taken together with the genus and is a constituent part of the substantial species. I also focus on a passage from Plotinus on the differentia (see Enn. VI 3[44], 5) which is apparently directed against Alexander, and I suggest that Simplicius reports Iamblichus’ criticism of Plotinus’ anti-Aristotelian stance. Both Porphyry and Iamblichus are credited with the view that differentiae are intermediate between substance and quality. As I aim to show, this conclusion requires some qualification. Porphyry essentially follows Alexander’s account of the substantial status of differentiae. Iamblichus, instead, emphasizes that the differentia, while being a completive feature of substance, is not a constituent part of substance and, therefore, cannot be regarded as a substance. I further analyze the controversy over the status of the differentia between Porphyry and Iamblichus and try to set their disagreement against the wider background of their metaphysical views.