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Home arrow Economics arrow Aquinas’s theory of perception: an analytic reconstruction

Seven Summary Propositions

In this discussion of Aquinas and the perception of individuals, the following seven propositions may be affirmed:

  • (a) The vis cogitativa is the faculty, which perceives the individuals of the world. In Aquinas’s ontology, these would be the primary substances, each of which is a hoc aliquid.
  • (b) The perception is of an individual of a natural kind.[1]
  • (c) This awareness transcends the limits of the external senses. The external senses are limited, given the structure of Aquinas’s philosophy of mind, to an awareness of proper and common sensibles.
  • (d) The awareness by the vis cogitativa is an ‘active contribution’ to the perceiving process necessary to be aware of individuals as individuals and not bundles of sensations.
  • (e) It follows from (a)-(d) above that Aquinas developed a philosophy of mind on the perceptual level necessary to provide for an awareness of individuals.
  • (f) This account of the awareness of an individual is in addition to the usual account of the reflexive awareness of the intellect so common to explications of Aquinas’s philosophy of mind. (Cf. Summa Theologiae, I q. 86 a 1: ‘Whether the Intellect knows Particulars’—i.e. Utrum Cognoscat Singularia.)
  • (g) It follows that Aquinas offers an account for the awareness of individuals as individual hoc aliquids on the level of sense perception.

The texts from the Summa Theologiae, the Summa Contra Gentiles, the Commentary on the Soul, and the Quaestiones Disputatae de Veritate that justify this account are noted above. Hence, the incidental object of sense is an example of an intentio non sensata. Its awareness comes through the intentional activity—the mental act—of the vis cogi- tativa. While in some texts the particular reason is equated with the vis cogitativa, in none of these texts is the ratio particularis identified with the intellectus possibilis.

The important question concerns the significance of all of this for Aquinas’s theory of sensation and perception. It appears that he provides a structured cognitive account for the perception of the individual. Since the intentiones non sensatae cannot come about through the external senses, there must be some active contribution—what might be called a ‘conditioning’ or ‘structuring’ of the mental act—on the part of the vis cogitativa which enables it to perceive individuals as substantival wholes of a natural kind and not just as mere bundles of sensations. In this case, Aquinas’s epistemological account is not a reception of a form immaterially in a simple-minded isomorphic way. There is a kind of isomorphism. But it is with the essence determining principle—the forma substantialis—in the individual. This individual is an individual of a natural kind. In other words, what the vis cogitativa knows as an individual is isomorphic with the primary substance existing outside the mind. The vis cogitativa permits Aquinas’s philosophy of mind to be realist and externalist and avoids the pitfalls of representationalism.

It appears that the vis cogitativa is the crucial sense faculty in Aquinas’s account of perception. It is by the conditioned awareness of this faculty that the individuals of the world, which in effect are the primary substances in the principal category of his ontology, are perceived. Insofar as Aquinas affirms the ontological existence of a world of individuals, he also provides the epistemological and philosophy-of-mind machinery necessary for a perceiver to be aware of these individuals. Furthermore, because a primary substance is an individual of a kind, which natural kind in Aquinas’s ontology is determined by a substantial form, the vis cogitativa is also aware of an individual as one belonging to a natural kind. The vis cogitativa explains, but in an un-Kantian fashion, the possibility for the perception of primary substances, which are the hoc aliquids of the world. In his Commentary on the Metaphysics, Thomas argues explicitly for the substantive existence of a hoc aliquid as a natured individual and not reducible to a Berkeleyian ‘heap of properties’ (bk XII, lect. 3, nos 2441-54).

This explicatio textus of Aquinas on the vis cogitativa, therefore, offers a way to account for the awareness of individuals independent of and quite different from the complex account of the reflexive act of the intellect, which Aquinas discusses in the

Summa Theologiae. This text is often used as the only one in which he considers how an individual as such is known. On the level of sense perception utilizing the internal sense of the vis cogitativa together with the notion of intentiones non sensatae, he transcends the limits of traditional empiricism. In this way, he would in principle accept the category difference between sensation and perception and thus agree with Wisdom’s distinction between ‘sense statements’ and ‘thing statements’. This all occurs, it must be emphasized, on the level of sense perception.[2]

If this analysis of Aquinas’s theory of perception is correct, then it poses an extremely interesting issue for students of the history of philosophy. Often Scotus is seen in opposition to Aquinas in that Aquinas did not, so the common argument goes, provide a way to account for direct knowledge of individuals. Hence Scotus, so the story develops, postulated the necessity for the individuator form, which he called haeccaeitas (thisness). If the account of Aquinas argued for above is correct, then it follows that he did possess the epistemological and philosophy-of-mind machinery in his philosophy of knowing necessary to explain the possibility for knowledge of individuals, at least on the perceptual level beyond the limits of the external sensorium. It would follow from this analysis that a difference between Aquinas and Scotus on the knowledge of individuals would be, not that Aquinas failed to provide such an account, but that the nature of the mental act differs in each philosopher’s analysis. In the manner of adopting a cognitive structure, Aquinas opts for a ‘structured mental act’. Scotus, on the other hand, apparently offers a ‘diaphanous mental act, which directly intuits the form of haeccaeitas. Haeccaeitas is needed as an object of the mental act for the awareness of individuals. With his acceptance of matter as the principle of individuation, it is not open to Aquinas to adopt an individuating form like the haeccaeitas of Scotus.

  • [1] In my judgement, in Aquinas’s ontology sortal properties (rooted in the formal cause) apply univocally only to natural kinds. Accordingly, there are no sortal properties for artefacts. For artefacts, the use ofsortal properties would be an analogical use of a formal cause.
  • [2] It would appear that Haldane in his 1983 essay on Aquinas and perception failed to appreciate this version of the vis cogitativa. Haldane expressed some concern that Aquinas could not reconcile the demands ofthe senses for discrete material-laden sensations with the universal aspect of the intellectus possibilis and theabstractive function of the intellectus agens. In this he falls prey to the same set of worries expressed by Fredein her analysis of inner sense in Aquinas. Haldane commented on the physicalist analysis of Aquinas putforward by Cohen: ‘Aquinas’s talk of “two grades of immaterial experience”, one fully fledged, the other “thehalf-way state of sensible being” is simply a vain attempt to combine incompatible features’: John Haldane,‘Aquinas on Sense-Perception, Philosophical Review 92(2) (1983), 233-9. The position articulated in thischapter elucidating the function of the vis cogitativa in terms of a structured mental act provides a way aroundthe misgivings that Haldane expressed about Aquinas’s supposed lack of connection between the sensibleimage in the imagination and the abstracted conceptus in the intellectus possibilis. Haldane appears to consideronly the vis imaginativa as an inner sense in Aquinas’s array of internal sense faculties.
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