Imagination rather than intellect is actually the main locus of human consciousness for both Thomas Aquinas and the great Aristotelian commentator Averroes whom Aquinas famously criticized, according to medieval scholar Deborah Black.
“[W]ithin the Aristotelian framework which Aquinas and Averroes share, the psychological explanation and interpretation of intellectual consciousness is not itself a given, even if the experience of consciousness is. Consciousness of thinking may play a central role in Cartesian philosophy, and in the system of Averroes’s and Aquinas’s predecessor, Avicenna. But it has no such privileged status in the philosophies of Aristotle, Averroes, or Aquinas, in which the possible intellect ‘is actually nothing before it thinks,’ and is only able to think itself after it has been actualized by some other object”, she wrote in her 1993 essay “Consciousness and Self-Knowledge in Aquinas’s Critique of Averroes’s Psychology”.
The relation of so-called “intellect” (nous) to the human “soul” (psyche) in Aristotle has historically been a major point of contention. These words are used in subtly or extremely different ways by many authors. I strongly recommend holding off on any easy identification of either of them with what modern people think of as subjective mind or consciousness.
Aristotle seems to apply a variant of his fruitful pairing of potentiality and actuality in his rather minimalist account of intellect. These notions were developed in greater detail in the commentary tradition. To hazard an oversimplification, intellect in actuality was considered to be something immaterial that makes things intelligible, whereas intellect in potentiality was considered to be something with no form of its own that takes on intelligible forms.
The great Greek commentator Alexander of Aphrodisias identified the potential or “material” intellect with a part of the soul, which he considered to be inseparable from the body, and therefore mortal. The actual or “agent” intellect he identified with a divine principle that he also gave a cosmological role.
The brilliant Arabic commentator Averroes (Ibn Rushd) argued that both aspects of intellect were symmetrically unique immaterial principles, outside the soul but connected with it. He became convinced that all humans must share a common “material” (potential) intellect, which grounds the real existence of logical universals and intelligible forms, but gets its contents from human imagination, and would not exist if there were no rational animals.
Aquinas located both intellects within the human soul, while giving the latter the elevated, more neoplatonic metaphysical status of an “intellectual soul”, and strongly associating its intellectual character with personal immortality. Especially in later works, Aquinas polemicized sharply against Averroes, claiming that Averroes could not even consistently say that “this human understands”, because for Averroes in his Long Commentary on the De Anima, there is only one material intellect shared by all humans.
Deborah Black argues that the two phases of intellect in Aristotle work together to constitute objects and intelligible forms. This need not imply an experience of immediate self-awareness. For Aristotle, Averroes, and Aquinas, intellectual self-awareness emerges only indirectly.
Black points out that Aquinas typically uses words like “perceives” or “experiences” in talking about self-awareness, and seems to deliberately avoid words implying intellectual comprehension. She sees this as reflecting Aristotelian scruples, and notes the studied vagueness of Aquinas’ endorsement of Augustinian immediate self-awareness. In his refutation of Averroes, Aquinas does appeal to the experience of consciousness, but she notes that he does so initially to argue against Plato’s identification of human being solely with intellect, pointing out that the same person perceives herself both to understand and to sense. “This human understands” does not actually emphasize any deep reflexivity, only individuality.
Aquinas approves of the fact that for Averroes, intellect is in some way united with the body, but argues that because for Averroes that union occurs only through a working of intellect on the contents of imagination, the human individual for Averroes does not herself think. On the other hand, Black argues that Aquinas does not take into account the fact that although what Aquinas himself calls imagination is an entirely passive reception of images, the contents of imagination for Averroes have a much more active character. For Averroes, according to Black, it is the active character of the contents of imagination that manifests human self-awareness. Because Aquinas views imagination as entirely passive, he refuses to acknowledge any credibility to this at all, claiming that the contents of imagination Averroes appeals to are really nothing more than the equivalent of inert colors on an inert wall, and that this makes the human equivalent to a wall.
Averroes compares active intellect to light, and so-called “material” intellect to a transparent medium such as air. Aquinas makes it sound as though the material intellect for Averroes would be analogous to the eye, which would make the material intellect a sort of mind behind our minds. However, Black says Averroes always compared it to a transparent medium, not to the eye. She argues that neither of Averroes’ intellects is a mind or a knower or subject in the modern sense. In her 2004 essay “Models of the Mind: Metaphysical Presuppositions of the Averroist and Thomistic Accounts of Intellection”, she contends that for Averroes, far from being the mind behind our minds that would make us into mere puppets, the material intellect serves as a shared instrument for human agents who individually constitute themselves in imagination.
Averroes’ notion of intellect, Black suggests, is mainly concerned with the constitution of intelligible objects as universals from imaginative content. It does not act as a subject in the modern sense. She cites a number of passages from Aquinas indicating that he, too, often treated intellect as an instrument, rather than as our very essence. (See also Parts of the Soul; Aristotelian Subjectivity Revisited.)