Chapter 4 — How the positions of Aristotle and Plato differ

There are other respects in which Plato and Aristotle differ. First, as has been said above, (Cf. above, Cap. I.) Plato posited a twofold order of immaterial substances above the souls of the heavens: namely, the intellects and the gods. He declared these gods were the separate intelligible forms, (Cf. St. Thomas, In Librum de Causis, Prop. 3 (ed. H. Saffrey, 18): “Ideo omnes hujusmodi formas sic subsistentes ‘deos’ vocabat.”) by participation in which the intellects have understanding. (Proclus, Elem, Props. 101, 161, 163 (pp. 91, 141, 143).) But Aristotle, since he did not posit any separate universals, posited only a single order of things above the souls of the heavens. He held, moreover, that the first among these was the highest God, just as Plato held that the highest God was first in the order of forms, among which the highest God is the very idea of the one and the good.

But Aristotle held that this order comprised both, namely, so that it was both understanding and understood, so that thus the highest God would understand not by participation in something higher that would be his perfection, but through his own essence. (Aristotle, Metaphysics, XI, 9 (1074b 33–35).) And Aristotle likewise held the same opinion as to the other separate substances ordered below the highest God, (Aristotle, Metaphysics, XI, 9 (1074a 10–16).) except that as they fall short of the simplicity of the first and of his highest perfection, their understanding can be perfected by participation in the higher substances. (Aristotle, Metaphysics, XI, 9 (1074b 26).) Thus, according to Aristotle, such substances, which are the ends of the heavenly motions, are both understanding intellects and intelligible forms. (Aristotle, Metaphysics, XI, 9 (1074b 35–1075a 5).) But this is not to be understood in the sense that they are the forms or natures of sensible substances, as the Platonists asserted, (Aristotle, Metaphysics, I, 6 (987b 1–10).) but altogether higher forms.

They differ, second, because Plato did not restrict the number of separate intellects to the number of heavenly movements. It was not on this account that Plato was moved to posit separate intellects, but rather by considering the very nature of things in themselves. Aristotle, on the other hand, not wishing to be diverted from sensible things, came to posit separate intellectual substances as a result of the sole consideration of motion, as we have said above, (Cf. above, Cap. II.) and for this reason, limited the number of the substances to the number of heavenly motions. (Cf. above, Cap. II.)

Third, they differ because Aristotle did not posit any souls intermediate between the souls of the heavens and the souls of men, as did Plato. (Cf. above, Cap. I; Cap. III; St. Augustine, De Civitate Dei, VIII, 13, 14, 16; IX, 2, 8, 12; X, 1 (PL 41, 237–239, 241–242, 257, 263, 265–266, 267–279).) Hence, we find that neither Aristotle nor any of his followers has made mention of demons.

This, then, is what we have gathered from various writings concerning the opinions of Plato and Aristotle on the separate substances. (This composite doctrine of Plato and Aristotle which St. Thomas uses in his critique of other philosophical positions in Cap. V–XVI has been advanced by C. Fabro, La nozione metafisica di Partecipazione secondo S. Tommaso d’Aquino, Turin, 2nd edit. 1950, as an argument for a real assimilation of the metaphysical content of the Platonic notion of participation within Aristotelian thought by the Angelic Doctor (pp. 58–64). R. Henle, on the other band, in A Note on Certain Textual Evidence in Fabro’s ‘La Nozione Metafisica di Partecipazione,’ 265–282 and in Saint Thomas’ Methodology in the Treatment of ‘Positiones’, 391–409, thoroughly disagrees with Fabro’s thesis.)