In IIa IIae, 8, 1, Thomas considers whether the human power of intellection should be considered a gift of the Holy Spirit. The intuitive objection is this: “Sed intellectus est quidam habitus naturalis in anima, quo cognoscuntur principia naturaliter nota.” Intellection seems to be a completely immanent process, so why posit an outside power pushing it along?
Indeed, in Thomas’s own terms, it’s tough to see why he sticks with calling intellection a grace. He adopts Aristotle’s account of intellect as operating by a “power” within the soul, which allows a person to penetrate “beneath” the external matter of a thing, to “read” its inner “essence.” Thomas grants that this power works well enough in immanent terms, but then insists that for the light of intellection to penetrate “further” into the nature of things requires grace (graced-intellection is something on the order of a souped-up ‘Vette):
Lumen autem naturale nostri intellectus est finitae virtutis, unde usque ad determinatum aliquid pertingere potest. Indiget igitur homo supernaturali lumine ut ulterius penetret ad cognoscendum quaedam quae per lumen naturale cognoscere non valet.
But how to determine the cut-off point? Might it not be that everything human beings do in fact intellect falls within the reach of their “natural” power of intellection? It seems to me that Thomas is hindered from securing the conclusion he recognizes as absolutely necessary (e.g., that there is no un-graced nature) by a problematic trope for conceptualizing knowledge: with Aristotle, Thomas has to posit a mysterious, god-like creature within the soul, a faculty that “sees essences” in a manner analogous to the human eye. If such a thing existed and operated in the way Thomas suggests, he will never be able to prevent the steady encroachment of nature’s operations on those of grace.
A simpler trope might be the one I (following Jenson) have toyed with some in recent posts: let’s think of knowing, not as seeing, but as hearing, and say that whatever we come to know is but the result of our being permitted to overhear the Trinitarian conversation that is creation. In this model, it is not a question of ocular clarity that determines knowledge, but rather of volume: the Word speaks more loudly in some places than in others (and loudest of all in Jesus, the infinite Word blaring forth in human flesh), and the Spirit livens the hearing of some more than others.