Man's Knowledge of Nonmaterial Things

Since the proper object of intellect, in the present earthlylife of man, is the essences of material things, the intellectunderstands by using phantasms, that is, sense-images of material things presented in imagination. Now, there are no phantasms ofnonmaterial things. Therefore, in this life, the human intellectcannot knownonmaterial things directly or per se. It cannot know, for example, what nonmaterial substances, such as angels, are in themselves.

We know material things by turning the light of the agent intellect on phantasms; this is a sort of intellectual X-ray which penetrates what is individual in the phantasms and shows up their essence. We call this process abstraction. We say that the intellect abstracts its ideas from phantasms. This is a kind of process of de-materializing and de-individualizing material things. And we can continue this process, refining more and more, drawing ideas from ideas, and reaching more and more abstract ideas. But wecan never attain by such a process to the perfect idea of spiritual substance as such. Spirit is an essence altogether different from matter; hence no process of de-materializing can reveal spirit asit is in itself.

We cannot, therefore, have a perfect knowledge of infinite spirit. By reasoning we can know God’s existence, and many of the divine attributes. But to know God directly in his spiritual essence is something we cannot have this side of heaven with its light of glory. Therefore, here on earth and exercising natural powers, man cannot know God directly in himself, but indirectly by reasoning back to the First Cause of creatures. Therefore those teachers are much mistaken who hold that the first thing known by the human intellect is God.