I answer that, As Augustine says (Gen. ad lit. lit. ii), such things as pre-existed from eternity in the Word of God, came forth from Him in two ways: first, into the angelic mind; and secondly, so as to subsist in their own natures. They proceeded into the angelic mind in such a way, that God impressed upon the angelic mind the images of the things which He produced in their own natural being. Now in the Word of God from eternity there existed not only the forms of corporeal things, but likewise the forms of all spiritual creatures. So in every one of these spiritual creatures, the forms of all things, both corporeal and spiritual, were impressed by the Word of God; yet so that in every angel there was impressed the form of his own species according to both its natural and its intelligible condition, so that he should subsist in the nature of his species, and understand himself by it; while the forms of other spiritual and corporeal natures were impressed in him only according to their intelligible natures, so that by such impressed species he might know corporeal and spiritual creatures.
Reply Obj. 1: The spiritual natures of the angels are distinguished from one another in a certain order, as was already observed (Q. 50, A. 4, ad 1, 2). So the nature of an angel does not hinder him from knowing the other angelic natures, since both the higher and lower bear affinity to his nature, the only difference being according to their various degrees of perfection.
Reply Obj. 2: The nature of cause and effect does not lead one angel to know another, except on account of likeness, so far as cause and effect are alike. Therefore if likeness without causality be admitted in the angels, this will suffice for one to know another.
Reply Obj. 3: One angel knows another by the species of such angel existing in his intellect, which differs from the angel whose image it is, not according to material and immaterial nature, but according to natural and intentional existence. The angel is himself a subsisting form in his natural being; but his species in the intellect of another angel is not so, for there it possesses only an intelligible existence. As the form of color on the wall has a natural existence; but, in the deferent medium, it has only intentional existence.
Reply Obj. 4: God made every creature proportionate to the universe which He determined to make. Therefore had God resolved to make more angels or more natures of things, He would have impressed more intelligible species in the angelic minds; as a builder who, if he had intended to build a larger house, would have made larger foundations. Hence, for God to add a new creature to the universe, means that He would add a new intelligible species to an angel. _______________________
THIRD ARTICLE [I, Q. 56, Art. 3]
Whether an Angel Knows God by His Own Natural Principles?
Objection 1: It would seem that the angels cannot know God by their natural principles. For Dionysius says (Div. Nom. i) that God "by His incomprehensible might is placed above all heavenly minds." Afterwards he adds that, "since He is above all substances, He is remote from all knowledge."
Obj. 2: Further, God is infinitely above the intellect of an angel. But what is infinitely beyond cannot be reached. Therefore it appears that an angel cannot know God by his natural principles.
Obj. 3: Further, it is written (1 Cor. 13:12): "We see now through a glass in a dark manner; but then face to face." From this it appears that there is a twofold knowledge of God; the one, whereby He is seen in His essence, according to which He is said to be seen face to face; the other whereby He is seen in the mirror of creatures. As was already shown (Q. 12, A. 4), an angel cannot have the former knowledge by his natural principles. Nor does vision through a mirror belong to the angels, since they do not derive their knowledge of God from sensible things, as Dionysius observes (Div. Nom. vii). Therefore the angels cannot know God by their natural powers.