Alexander of Aphrodisias
Alexander of Aphrodisias, who was teaching at Athens in 200 CE, was recognized for centuries as the most authoritative exponent of Aristotle. His influence has probably been most far-reaching in the development of the theory of universals because he emphasized certain elements in Aristotle's not always unambiguous account. These were the unqualified priority of the particular substance and the existence of universals only as concepts, or "acts of intellect." The form was what made "this" matter (that is, an identifiable piece) what it was, but it was contingent whether the form was universal in the sense of generic. (Alexander does not notice that a class with only one member, like his case of the sun, is still a class.) What the form is as a subject remains unclear.
More famous is his doctrine about soul and intellect. A human being's intellectual faculty can exist in three conditions, described as three intellects: (1) the "material" intellect (intellectus possibilis), which is nothing actual but the bare potentiality (so Aristotelian matter) of the body to develop reason—the condition of babies; (2) the intellect (intellectus in habitu) that is the possession of, in fact, is identical with, concepts, or universals gained from sense experience—the condition of adults; (3) the "active" intellect (intellectus agens), which is exercising the thoughts that form the intellectus in habitu and is thus equivalent to the intellect as aware of itself.
What is distinctively Alexandrist is the identification he made, or seemingly made, of the "active" intellect both with the intellect that Aristotle said entered the body "from outside" and with the intellect eternally thinking of itself that Aristotle said was God. Intellect was, of course, the highest part or function of the soul, but since only the "active" intellect, as a "separate form," could exist without matter, it followed that there was no individual immortality for human beings. The exact relation of the "active" intellect to the individual soul or intellect is obscure in Alexander. He does not describe an active intellect acting directly like an efficient or even formal cause on a passive intellect but suggests rather the quasi-logical relationship which was fundamental to Neoplatonism and which made the less perfect instance of a kind entail the existence of the perfect. Thus, it is not at all certain that he meant thinking itself to go the way of immortality. In the fifteenth century Italian philosophers known as Alexandristi defended this interpretation of Aristotle's psychology against both Averroes's version and the theologically orthodox version of Themistius and Thomas Aquinas.
In other subjects we see Alexander less original but often attacking Stoic doctrine, notably in his tracts On Fate and On Mixture. But the exact understanding of him is colored always by the difficulty of knowing how far we can trust the writings attributed to him. The commentary on Books E (VI) to N (XIV) of Aristotle's Metaphysics and parts of Book II of his own De Anima are probably not his. The latter includes the section On Intellect which greatly influenced later Greek, Arab, and medieval philosophers. But both may well depend on and be closer to his thought than is allowed by a modern tradition that underestimates Neoplatonizing features of Aristotle as well as of Alexander.
Aristotle; Averroes; Neoplatonism; Themistius; Thomas Aquinas, St.; Universals, a Historical Survey.
Bibliography
Alexander's works, including dubious ones, are in Commentaria in Aristotelem Graeca, Vols. I–III, and Supplementum Aristotelicum, Vol. II (Berlin, 1883–1901). P. Moraux, Alexandre a'Aphrodise, exégète de la noétique d'Aristote (Paris, 1942), includes a French translation of On Intellect. See also F. E. Cranz, in Catalogus Translationum et Commentariorum: Mediaeval and Renaissance Latin Translations and Commentaries, Vol. I (Washington, DC: Catholic University of America Press, 1960), pp. 77–135; Ernst Cassirer, Das Erkenntnisproblem, 3rd ed., Part I, "Die Reform der aristotelischen Psychologie" (Berlin: Cassirer, 1922); and J. H. Randall Jr., The School of Padua and the Emergence of Modern Science (Padua, 1961).
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