Aquinas articulates structural connections with Reid’s philosophy of mind. In considering the role of common sense as foundational for the philosophical enterprise, Aquinas is akin philosophically to Reid. On matters of perception, Aquinas— and, as Deely argues, John Poinsot—are kindred spirits with Reid in differing radically from Hume.11 Deely remarks perspicuously that Reid ‘was, as it were, the one man of the eighteenth century who stood up and said: “the emperor has no clothes on” ’, 
The explicatio textus of sense organ and faculty found in the Commentary is remarkably similar to the method articulated by Gibson in discussing the evolutionary development of human sense organs. Aquinas adopts a similar metaphilosophy in approaching issues in sensation and perception. This interpretation gives a certain value to Aquinas’s oft-repeated claim that ‘nature does not act in vain’ and ‘the knowing faculty is made for the act of knowing, which in turn is made for the obj ect of knowing’. These teleological claims in Aquinas may be his mode of introducing ‘epistemological naturalism’ into the philosophy-of-mind discussion of cognitive faculties. In other words, human knowing faculties are made—or develop—for a particular environment (which is Gibson’s claim). The external and the internal sense faculties are what they are because the objects of sensation and perception are what they are.
In addition, what is important for this discussion is Reid’s consistent affirmation of the distinction between sensation and perception. Mental acts of perception are aware cognitively of individual things and not of discrete sensibles or sense data. Furthermore, Reid argues that only perception is cognitive. The important philosophical question, however, concerns what grounds Reid offers to justify philosophically this distinction between sensation and perception. Reid, in discussing how a human perceiver is aware directly of things and not ideas, suggests that it is by means of ‘natural signs’ that a perceiver ‘comprehends those [things] which, though we never before had any notion or conception of the thing signified, do suggest it, or conjure it up, as it were, by a natural kind of magic’. Reid goes on to suggest that ‘by all rules of just reasoning, we must conclude that this connection [i.e. between mind and thing] is the effect of our constitution, and ought to be considered as an original principle of human nature’.
Structurally, Aquinas adopts Reid’s position in rooting cognitive abilities in human nature, but his naturalism attempts to spell out how these cognitive abilities develop and work. The vis cogitativa is rooted in human nature through the innate cognitive dispositions grounded in the substantial form of the human natural kind. Throughout his entire analysis of direct perception of things in the external world, Reid dismisses as philosophically faulty any theory of representationalism. He wrote that representationalism ‘will not solve the problem [. . . ] for who will interpret the [representation or symbol]; [. . . ] symbols without an interpretation have no value [and it is] clear that the hypothesis of ideas [representationalism] increases the difficulties of perception and meaning and in no way diminishes them, and for this reason it is scarcely suitable for an explanation or elucidation of the phenomena of these [cognitive] faculties.’
In order to provide some semblance of an account for these ‘faculties, Reid appeals to the Author of nature’ who set up our perceptual apparatus so that it can function in a common sense manner. Reid writes: ‘The wise Author of our nature intended that a great and necessary part of our knowledge should be derived from experience before we are capable of remembering, and he hath provided means perfectly adequate to this intention.’ Deely is concerned about this lack of philosophical analysis on Reid’s part justifying the distinction between sensation and perception.
This present conceptual elucidation proposes that the mental act of the vis cogitativa enables Aquinas to affirm the distinction between sensation of accidental qualities— the proper and the common sensibles—and the perception of the individual primary substance as a thing. This entails postulating an internal cognitive structure to the mental act of the vis cogitativa that permits it to perceive an individual primary substance as such and not merely as a collection or bundle of sense qualities.
-  Haldane commingled Reid with Aquinas on perception: ‘Like Thomas Reid [...] Aquinas himself is simply trying to identify at the level of a metaphysical description what is implicit in our everyday dealings with the world’: John Haldane, ‘Forms of Thought’ in Lewis Edwin Hahn (ed.), The Philosophy of RoderickM. Chisholm (Chicago: University of Chicago Press, 1997), 167.
-  Deely, Four Ages of Understanding, 548.
-  Haldane once observed wryly that at the end of the day, Reid throws up his hands and utterssomething like: ‘It’s magic!’
-  Thomas Reid, Inquiry and Essays, ed. Ronald E. Beanblossom and Keith Lehrer (Indianapolis:Hackett, 1983), 43-4.
-  Ibid.
-  The Philosophical Orations of Thomas Reid, ed. D. D. Todd (Carbondale, Ill.: Southern IllinoisUniversity Press, 1989), 62.
-  Thomas Reid, An Inquiry into the Human Mind’, in Louis Schneider (ed.), The Scottish Moralists onHuman Nature and Society (Chicago: University of Chicago Press, 1967), 25. Stump, in referring to a divinejustification for reliabilism in Aquinas’s philosophy of mind, appears to adopt a position similar to Reid’sjustification. McDonald hints at such a possible resolution to the reliabilism problem in Aquinas.
-  Deely wrote: ‘Reid’s valiant effort to establish principles of common sense in modern philosophy,viewed in the light of earlier Latin developments in epistemology, had one great shortcoming whichuncorrected, could only doom the effort. While Reid rejected the proposition that we directly knowonly our own ideas, which is the bedrock of modern epistemology, he did so without having a wayeffectively to discriminate between sensation and perception as such. Hence, he made his case of directknowledge of physical things so strong as to be unable to deal as a matter of principle with the fundamentaldifference between perceptual objects in their objective constitution through relations and perceptualobjects in what they have of a subjective constitution as things accessible in sensation’ (Four Ages ofUnderstanding, 548; emphasis added). For a more detailed discussion of Deely’s account of sensationand perception, with special reference to John Poinsot, see Anthony J. Lisska, ‘Deely, Aquinas andPoinsot: How the Intentionality of Inner Sense Transcends the Limits of Empiricism’, Semiotica 178(2010), 135-67.
-  In discussing the perception/sensation distinction, Deely writes precious little about the vis cogitativa.Nonetheless, he is one of a small group of philosophers considering medieval texts who pay serious attention to Aquinas’s distinction between perception and sensation.