The Priority of Natures against The Identity of Indiscernibles: Alexander of Aphrodisias, Yaḥyā b. 'Adī, and Avicenna on Genus as Matter
- Journal of the History of Philosophy
- Johns Hopkins University Press
- Volume 57, Number 2, April 2019
- pp. 205-234
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When one studies the history of universals in late antiquity and in the Arabic and Latin Middle Ages, the key notion is 'nature.' Natures are notions like 'redness qua redness,' which are neither universal nor particular in themselves, but are immanent either in universals, which exist only in the mind, or in extramental particulars. All recent studies agree that Alexander of Aphrodisias probably developed the idea of 'nature.' Then it travelled either directly or via the Baghdad Peripatetic Yaḥyā b. 'Adī to Avicenna. From Avicenna, it was transmitted to thinkers of Latin Scholasticism, for instance, Thomas Aquinas and Duns Scotus. In this paper, I will show that this historical reconstruction of the inheritance of the notion of 'nature' neglects an important shift in the middle of the historical chain: natures are ontologically prior to their instances in Alexander and Ibn 'Adī, but posterior in Avicenna. This crucial difference will be shown on the basis of the parallel between (a) natures and universals, and (b) the material and generic aspects of common notions. We will see that Avicenna's reason for disagreeing with the previous tradition on this parallel was a concern regarding the compatibility of the priority of natures with the principle of the identity of indiscernibles.