The medieval synthesis of pagan philosophy and Christian theology in Albert and Aquinas may have drawn from five principal sources: (i) biblical scripture; (ii) Aristotle; (iii) Augustine; (iv) Pseudo-Dionysius; and (v) Avicenna. Although Platonic elements may be found in all of these sources, Aquinas consistently labours to distinguish his thought from its Platonic inheritance. (See especially his Commentary on Pseusdo-Dionysius’ the Divine Names (17)) And although Aquinas has no full-length work on Plato and the Platonists, he consistently follows Aristotle in attacking the via Platonica for separating, duplicating, and reifying the logical intentions of the mind as universal forms in separated substances. R. J. Henle summarizes Saint Thomas’ objections:
“The Platonic theory [of Ideas] requires that we maintain that the Idea (1) is truly separated in being, (2) is truly one, (3) is the real formal cause of the particulars, (4) is truly related to them as a cause, a principle, a justification of knowledge, of predication and of being. If the separation is stressed, the theory tends towards pure extrinsecism; if the invasion of the particulars is stressed, the unity of the form drives towards entitative union and pantheism. These ambiguities and tensions are thus inherent in the pure Theory of Ideas. As we have seen, Saint Thomas himself recognizes these different pressures and their logical conclusions.” (Saint Thomas and Platonism,1970, p.378)
Aquinas’ central criticism is that Plato has externally reflected the ideas of the mind into separated substances that are meant to cause all particular phenomena. The result, Henle alleges, is either to cast the ideas of all possible cognition into extrinsic separation from phenomenal world, or to colonize the world with these concepts, until the creator-creation distinction is reduced to a pantheistic system of univocal concepts. Henle concludes:
“The Platonic argument thus doubles the ontological correlates for natural knowledge, but, by insisting that the separated form is what we truly know, it casts a shadow on the metaphysical structure of the material entity, obscuring the intrinsic form and rendering its status in being and knowledge extremely ambiguous.” (375)
Henle acknowledges (341) that Aquinas’ central criticism of separated substance is derived directly from Aristotle’s Metaphysics (Bk. I ch.4), where Aristotle summarizes:
“Plato accepted [Socrates’] teaching, but held that the problem applied not to sensible things but to entities of another kind-for this reason, that the common definition could not be a definition of any sensible thing, as they were always changing. Things of this other sort, then, he called Ideas, and sensible things, he said, were all named after these, and in virtue of a relation to these; for the many existed by participation in the Ideas that have the same name as they. Only the name 'participation' was new; for the Pythagoreans say that things exist by 'imitation' of numbers, and Plato says they exist by participation, changing the name. But what the participation or the imitation of the Forms could be they left an open question. Yet what happens is the contrary; the theory is not a reasonable one. For they make many things out of the matter, and the form generates only once, but what we observe is that one table is made from one matter.”
Here Aristotle describes how, in response to the Heraclitean Flux of sensible things that ‘were always changing’, Plato recast Socrates’ definitions as unchanging supersensible entities of reason, which he called Ideas. Later Aristotle represents these Ideas as separate substances:
“For it is evident that they are one in their intelligible expression, for one will express the same notion in speaking of each. Therefore, if there is a man-in-himself, who is a particular thing and is separate, the things of which he is composed, such as animal and two-footed, must also signify particular things and be separable and be substances.” (Metaphysics 1039a)
Saint Thomas comments:
“[Aristotle] accordingly says, first, that it is evident that the animal present in man and that present in horse are one and the same in their intelligible expression… Hence, if, because of the fact that species are predicated of all individuals according to one intelligible expression, there is a common man, who is man-in-himself, existing by himself, “and who is a particular thing,” i.e., something subsistent which can be pointed to and is separable from sensible things, as the Platonists maintained… [But] it is not possible for some one thing to be present in many things which exist separately. For you are present only in yourself, since you are not in many things which exist separately, as in flesh and bones, which are your parts. Therefore, if animal is one and the same, it will be incapable of existing in many species, as in man and in horse, since the separate Forms, according to the Platonists, are substances which are distinct from each other.”
Aquinas, following Aristotle, infers that Plato’s argument from science (Rep. 477b) implies that the ideas must be necessary, immutable, and separate substances from mutable material world. Since everything in the world consists in matter in motion, the immateriality and immobility of the Ideas seems to place them beyond the world. Since Ideas are supersensible, they must also be super-substantial separated substances. Plato’s separate substances are thus alleged to have illegitimately hypostatized logical intentions into a duplicate parallel reality. This duplicated reality of Ideas is considered to be illegitimate because, contrary to its scientific purpose, it cannot begin to explain the sensible world. Henle thus summarizes (343) six arguments that Aquinas made against Plato:
“1. The Ideas cannot be causes of motion or transmutation precisely because they were set up to explain the immobility of science and are therefore principles of immobility rather than of change.
2. They cannot serve to explain knowledge of the sensibilia because they are separated from them.
3. They cannot be exemplar principles because – aside from the metaphorical character of this assertion – (a) as separated exemplars they would render the obvious agency of immediate natural causes superfluous.
4. The Ideas cannot be the formal intrinsic causes of material individuals since they are separated.
5. They cannot explain becoming.
6. Moreover, the Platonists are inconsistent, for they do not posit Ideas of artefacts.”
Henle’s six arguments, from beginning to end, each depend upon the contention that Platonic Ideas are separated substances: for Ideas may only be considered immobile, supersensible, non-natural, extrinsic, and natural beings once they have been separated from the mobile, sensible, natural, and intrinsic productivity of the world that is becoming. It may come as a surprise, then, that, not only did Plato never describe Ideas as separate substances, but he even insisted that the Ideas can never be so separated from the world: Plato criticizes the spurious separation of the Ideas from the world in his criticism of the idealist ‘friends of the gods’ (Sophist 246a-249d); the separation of the universals forms from particulars instances in the Greatest Difficulty Argument (Parmenides 133a-134a); and even represents the forms as constituted of the elemental building blocks of the world in the Timaeus. (28a-31b) Although Thomas Aquinas could have had access to Calcidus’ early Latin translation of Plato’s Timaeus, Henle acknowledges that he overlooked this important later development. (325)
Aristotle, who was in the best position to know Plato’s doctrines, seems to have represented Platonic Ideas as separated forms for the purpose of distinguishing himself from and reformulating Plato’s forms. He indicates that because the sensible things of the world are “always changing”, and Plato’s Ideas are supersensible entities of reason, the Ideas must be separated from the sensible things of the world. Yet Plato’s insistence on the supersensibility is not meant to imply an ontic separation of forms from substances, but rather an even more intimate ontological bond between the Ideas and the word: for since the perfect paradigms of all predicate-properties (e.g. largeness) are the onto-noetic condition for the intelligibility and being of every imperfect instance (e.g. something large), there is an immediate ontological continuity between the paradigms and their instances that is only logically distinguished by their universal and particular scope. The impartation of the intelligibility and being of perfect paradigms into imperfect instances thus constitutes a kind of hyper-dynamic ontological motion beyond the observable dynamics of physical motion. And since these paradigms may only be thought as the universal predicates of sensible properties, even the most abstract paradigms must be thought through a kind of hyper-intuition beyond sensible intuition.
Aquinas’ criticisms of Plato are thus directly derived from Aristotle’s misrepresentation of Plato’s ontology for the purpose of advancing his own competing substance-metaphysics. In fact, it is Aristotle’s substance-metaphysics rather than Plato’s ontology that is most responsible for introducing so many sharp philosophic divisions between form and matter, intention and existence, logic and nature. Once it is recognized that Plato’s Ideas were never conceived as separate substances, it becomes possible to respond to Aquinas’ criticisms of Plato:
1. Ideas can impart motion because each of perfect paradigm imparts a hyper-dynamic motion into the imperfect instances.
2. Ideas can explain sensibilia because each of the paradigms is the hyper-intuited exemplar of sensible exemplifications.
3. Since the Principles, Ideas, and forms are the originary onto-noetic source of all intelligibility and being, there is no originary division of the mythical, metaphoric, linguistic or logical from the real entities of nature. Hence, natural causes should be explained, along with all other orders of causation, through the formal relations of Ideas emanating from the supreme Principle of the Good.
4. Since there is an immediate ontological continuity between paradigms and exemplifications, the Ideas are never extrinsic to material substances.
5. The Ideas are, not only not static, but are indeed the originary hyper-dynamic source of ‘becoming’ in logic, nature, and society.
6. The hyper-dynamic ‘becoming’ of the Ideas in human society implies that the Ideas can be continually reconstructed into artefacts, such as mathematical objects and even an Idea of a bed. (Rep. 596b)
Aquinas seems to have followed Aristotle in making two critical mistakes: first, he adopts Aristotle’s distinction of form and matter, in which the material world is distinguished from its forms; and then, on the basis of this first distinction, he concludes that the necessity, immutability, and separation of the Platonic forms are incompatible with materiality, mobility, and interpenetration. These mistakes did not originate with Plato, nor even with Aquinas who did not possess all of Plato's texts, but rather in Aristotle’s own substance metaphysics, which he afterwards interpolated into his interpretation of Plato when he characterized the Ideas as ‘separated substances’. For Plato, to the contrary, the Ideas are not separated but connected to all ‘substances’ through an unbreakable ontological continuum that hyper-dynamically imparts the intelligibility and being of perfect paradigms to imperfect exemplifications; and the ‘matter’ (from ‘hyle’ meaning ‘wood’) is merely a metonym for the passive matrix into which all forms are plastically received to take shape. Aristotle’s suggestion that Plato’s supersensible Ideas must be separate substances, in which universal forms are cast beyond the mobile and material world, can thus be nothing less than a deliberate misrepresentation of Plato’s authentic doctrines.
See also my lecture Plato, Logic, and Ontology:
See also my critical commentary on Aristotle' criticisms of Plato's mathematical Ideas:
See also my critical commentary on Aristotle' criticisms of Plato's mathematical Ideas: