To understand how one angel speaks to another, we must consider that, as we explained above (Q. 82, A. 4), when treating of the actions and powers of the soul, the will moves the intellect to its operation. Now an intelligible object is present to the intellect in three ways; first, habitually, or in the memory, as Augustine says (De Trin. xiv, 6, 7); secondly, as actually considered or conceived; thirdly, as related to something else. And it is clear that the intelligible object passes from the first to the second stage by the command of the will, and hence in the definition of habit these words occur, "which anyone uses when he wills." So likewise the intelligible object passes from the second to the third stage by the will; for by the will the concept of the mind is ordered to something else, as, for instance, either to the performing of an action, or to being made known to another. Now when the mind turns itself to the actual consideration of any habitual knowledge, then a person speaks to himself; for the concept of the mind is called "the interior word." And by the fact that the concept of the angelic mind is ordered to be made known to another by the will of the angel himself, the concept of one angel is made known to another; and in this way one angel speaks to another; for to speak to another only means to make known the mental concept to another.
Reply Obj. 1: Our mental concept is hidden by a twofold obstacle. The first is in the will, which can retain the mental concept within, or can direct it externally. In this way God alone can see the mind of another, according to 1 Cor. 2:11: "What man knoweth the things of a man, but the spirit of a man that is in him?" The other obstacle whereby the mental concept is excluded from another one's knowledge, comes from the body; and so it happens that even when the will directs the concept of the mind to make itself known, it is not at once make known to another; but some sensible sign must be used. Gregory alludes to this fact when he says (Moral. ii): "To other eyes we seem to stand aloof as it were behind the wall of the body; and when we wish to make ourselves known, we go out as it were by the door of the tongue to show what we really are." But an angel is under no such obstacle, and so he can make his concept known to another at once.
Reply Obj. 2: External speech, made by the voice, is a necessity for us on account of the obstacle of the body. Hence it does not befit an angel; but only interior speech belongs to him, and this includes not only the interior speech by mental concept, but also its being ordered to another's knowledge by the will. So the tongue of an angel is called metaphorically the angel's power, whereby he manifests his mental concept.
Reply Obj. 3: There is no need to draw the attention of the good angels, inasmuch as they always see each other in the Word; for as one ever sees the other, so he ever sees what is ordered to himself. But because by their very nature they can speak to each other, and even now the bad angels speak to each other, we must say that the intellect is moved by the intelligible object just as sense is affected by the sensible object. Therefore, as sense is aroused by the sensible object, so the mind of an angel can be aroused to attention by some intelligible power. _______________________
SECOND ARTICLE [I, Q. 107, Art. 2]
Whether the Inferior Angel Speaks to the Superior?
Objection 1: It would seem that the inferior angel does not speak to the superior. For on the text (1 Cor. 13:1), "If I speak with the tongues of men and of angels," a gloss remarks that the speech of the angels is an enlightenment whereby the superior enlightens the inferior. But the inferior never enlightens the superior, as was above explained (Q. 106, A. 3). Therefore neither do the inferior speak to the superior.
Obj. 2: Further, as was said above (Q. 106, A. 1), to enlighten means merely to acquaint one man of what is known to another; and this is to speak. Therefore to speak and to enlighten are the same; so the same conclusion follows.
Obj. 3: Further, Gregory says (Moral. ii): "God speaks to the angels by the very fact that He shows to their hearts His hidden and invisible things." But this is to enlighten them. Therefore, whenever God speaks, He enlightens. In the same way every angelic speech is an enlightening. Therefore an inferior angel can in no way speak to a superior angel.
On the contrary, According to the exposition of Dionysius (Coel. Hier. vii), the inferior angels said to the superior: "Who is this King of Glory?"