HKB
itself, it attains to some knowledge of incorporeal substances, such as is within its compass; not that the knowledge of itself gives it a perfect and absolute knowledge of them.
Reply Obj. 2: The likeness of nature is not a sufficient cause of knowledge; otherwise what Empedocles said would be true--that the soul needs to have the nature of all in order to know all. But knowledge requires that the likeness of the thing known be in the knower, as a kind of form thereof. Now our passive intellect, in the present state of life, is such that it can be informed with similitudes abstracted from phantasms: and therefore it knows material things rather than immaterial substances.
Reply Obj. 3: There must needs be some proportion between the object and the faculty of knowledge; such as of the active to the passive, and of perfection to the perfectible. Hence that sensible objects of great power are not grasped by the senses, is due not merely to the fact that they corrupt the organ, but also to their being improportionate to the sensitive power. And thus it is that immaterial substances are improportionate to our intellect, in our present state of life, so that it cannot understand them.
Reply Obj. 4: This argument of the Commentator fails in several ways. First, because if separate substances are not understood by us, it does not follow that they are not understood by any intellect; for they are understood by themselves, and by one another.
Secondly, to be understood by us is not the end of separate substances: while only that is vain and purposeless, which fails to attain its end. It does not follow, therefore, that immaterial substances are purposeless, even if they are not understood by us at all.
Reply Obj. 5: Sense knows bodies, whether superior or inferior, in the same way, that is, by the sensible acting on the organ. But we do not understand material and immaterial substances in the same way. The former we understand by a process of abstraction, which is impossible in the case of the latter, for there are no phantasms of what is immaterial.
SECOND ARTICLE [I, Q. 88, Art. 2]
Whether Our Intellect Can Understand Immaterial Substances Through Its Knowledge of Material Things?
Objection 1: It would seem that our intellect can know immaterial substances through the knowledge of material things. For Dionysius says (Coel. Hier. i) that "the human mind cannot be raised up to immaterial contemplation of the heavenly hierarchies, unless it is led thereto by material guidance according to its own nature." Therefore we can be led by material things to know immaterial substances.
Obj. 2: Further, science resides in the intellect. But there are sciences and definitions of immaterial substances; for Damascene defines an angel (De Fide Orth. ii, 3); and we find angels treated of both in theology and philosophy. Therefore immaterial substances can be understood by us.
Obj. 3: Further, the human soul belongs to the genus of immaterial substances. But it can be understood by us through its act by which it understands material things. Therefore also other material substances can be understood by us, through their material effects.
Obj. 4: Further, the only cause which cannot be comprehended through its effects is that which is infinitely distant from them, and this belongs to God alone. Therefore other created immaterial substances can be understood by us through material things.
On the contrary, Dionysius says (Div. Nom. i) that "intelligible things cannot be understood through sensible things, nor composite things through simple, nor incorporeal through corporeal."