Reply Obj. 2: Although one angel sees the intelligible species of another, by the fact that the species are proportioned to the rank of these substances according to greater or lesser universality, yet it does not follow that one knows how far another makes use of them by actual consideration.
Reply Obj. 3: The appetite of the brute does not control its act, but follows the impression of some other corporeal or spiritual cause. Since, therefore, the angels know corporeal things and their dispositions, they can thereby know what is passing in the appetite or in the imaginative apprehension of the brute beasts, and even of man, in so far as the sensitive appetite sometimes, through following some bodily impression, influences his conduct, as always happens in brutes. Yet the angels do not necessarily know the movement of the sensitive appetite and the imaginative apprehension of man in so far as these are moved by the will and reason; because, even the lower part of the soul has some share of reason, as obeying its ruler, as is said in Ethics iii, 12. But it does not follow that, if the angel knows what is passing through man's sensitive appetite or imagination, he knows what is in the thought or will: because the intellect or will is not subject to the sensitive appetite or the imagination, but can make various uses of them. _______________________
FIFTH ARTICLE [I, Q. 57, Art. 5]
Whether the Angels Know the Mysteries of Grace?
Objection 1: It would seem that the angels know mysteries of grace. For, the mystery of the Incarnation is the most excellent of all mysteries. But the angels knew of it from the beginning; for Augustine says (Gen. ad lit. v, 19): "This mystery was hidden in God through the ages, yet so that it was known to the princes and powers in heavenly places." And the Apostle says (1 Tim. 3:16): "That great mystery of godliness appeared unto angels*." [*Vulg.: 'Great is the mystery of godliness, which . . . appeared unto angels.'] Therefore the angels know the mysteries of grace.
Obj. 2: Further, the reasons of all mysteries of grace are contained in the Divine wisdom. But the angels behold God's wisdom, which is His essence. Therefore they know the mysteries of grace.
Obj. 3: Further, the prophets are enlightened by the angels, as is clear from Dionysius (Coel. Hier. iv). But the prophets knew mysteries of grace; for it is said (Amos 3:7): "For the Lord God doth nothing without revealing His secret to His servants the prophets." Therefore angels know the mysteries of grace.
On the contrary, No one learns what he knows already. Yet even the highest angels seek out and learn mysteries of grace. For it is stated (Coel. Hier. vii) that "Sacred Scripture describes some heavenly essences as questioning Jesus, and learning from Him the knowledge of His Divine work for us; and Jesus as teaching them directly": as is evident in Isa. 63:1, where, on the angels asking, "Who is he who cometh up from Edom?" Jesus answered, "It is I, Who speak justice." Therefore the angels do not know mysteries of grace.
I answer that, There is a twofold knowledge in the angel. The first is his natural knowledge, according to which he knows things both by his essence, and by innate species. By such knowledge the angels cannot know mysteries of grace. For these mysteries depend upon the pure will of God: and if an angel cannot learn the thoughts of another angel, which depend upon the will of such angel, much less can he ascertain what depends entirely upon God's will. The Apostle reasons in this fashion (1 Cor. 2:11): "No one knoweth the things of a man [*Vulg.: 'What man knoweth the things of a man, but . . . ?'], but the spirit of a man that is in him." So, "the things also that are of God no man knoweth but the Spirit of God."
There is another knowledge of the angels, which renders them happy; it is the knowledge whereby they see the Word, and things in the Word. By such vision they know mysteries of grace, but not all mysteries: nor do they all know them equally; but just as God wills them to learn by revelation; as the Apostle says (1 Cor. 2:10): "But to us God hath revealed them through His Spirit"; yet so that the higher angels beholding the Divine wisdom more clearly, learn more and deeper mysteries in the vision of God, which mysteries they communicate to the lower angels by enlightening them. Some of these mysteries they knew from the very beginning of their creation; others they are taught afterwards, as befits their ministrations.