mode of the knower. Now since the mode of the divine essence is higher than that of creatures, divine knowledge does not exist in God after the mode of created knowledge, so as to be universal or particular, or habitual, or potential, or existing according to any such mode.
Whether God understands Himself?
Objection 1: It seems that God does not understand Himself. For it is said by the Philosopher (De Causis), "Every knower who knows his own essence, returns completely to his own essence." But God does not go out from His own essence, nor is He moved at all; thus He cannot return to His own essence. Therefore He does not know His own essence.
Objection 2: Further, to understand is a kind of passion and movement, as the Philosopher says (De Anima iii); and knowledge also is a kind of assimilation to the object known; and the thing known is the perfection of the knower. But nothing is moved, or suffers, or is made perfect by itself, "nor," as Hilary says (De Trin. iii), "is a thing its own likeness." Therefore God does not understand Himself.
Objection 3: Further, we are like to God chiefly in our intellect, because we are the image of God in our mind, as Augustine says (Gen. ad lit. vi). But our intellect understands itself, only as it understands other things, as is said in De Anima iii. Therefore God understands Himself only so far perchance as He understands other things.
On the contrary, It is written: "The things that are of God no man knoweth, but the Spirit of God" (1 Cor. 2:11).
I answer that, God understands Himself through Himself. In proof whereof it must be known that although in operations which pass to an external effect, the object of the operation, which is taken as the term, exists outside the operator; nevertheless in operations that remain in the operator, the object signified as the term of operation, resides in the operator; and accordingly as it is in the operator, the operation is actual. Hence the Philosopher says (De Anima iii) that "the sensible in act is sense in act, and the intelligible in act is intellect in act." For the reason why we actually feel or know a thing is because our intellect or sense is actually informed by the sensible or intelligible species. And because of this only, it follows that sense or intellect is distinct from the sensible or intelligible object, since both are in potentiality.
Since therefore God has nothing in Him of potentiality, but is pure act, His intellect and its object are altogether the same; so that He neither is without the intelligible species, as is the case with our intellect when it understands potentially; nor does the intelligible species differ from the substance of the divine intellect, as it differs in our intellect when it understands actually; but the intelligible species itself is the divine intellect itself, and thus God understands Himself through Himself.
Reply to Objection 1: Return to its own essence means only that a thing subsists in itself. Inasmuch as the form perfects the matter by giving it existence, it is in a certain way diffused in it; and it returns to itself inasmuch as it has existence in itself. Therefore those cognitive faculties which are not subsisting, but are the acts of organs, do not know themselves, as in the case of each of the senses; whereas those cognitive faculties which are subsisting, know themselves; hence it is said in De Causis that, "whoever knows his essence returns to it." Now it supremely belongs to God to be self-subsisting. Hence according to this mode of speaking, He supremely returns to His own essence, and knows Himself.
Reply to Objection 2: Movement and passion are taken equivocally, according as to understand is described as a kind of movement or passion, as stated in De Anima iii. For to understand is not a movement that is an act of something imperfect passing from one to another, but it is an act, existing in the agent itself, of something perfect. Likewise that the intellect is perfected by the intelligible object, i.e. is assimilated to it, this belongs to an intellect which is sometimes in potentiality; because the fact of its being in a state of potentiality makes it differ from the intelligible object and assimilates it thereto through the intelligible species, which is the likeness of the thing understood, and makes it to be perfected thereby, as potentiality is perfected by act. On the other hand, the divine intellect, which is no way in potentiality, is not perfected by the intelligible object, nor is it assimilated thereto, but is its own perfection, and its own intelligible object.
Reply to Objection 3: Existence in nature does not belong to primary matter, which is a potentiality, unless it is reduced to act by a form. Now our passive intellect has the same relation to intelligible objects as primary matter has to natural things; for it is in potentiality as regards intelligible objects, just as primary matter is to natural things. Hence our passive intellect can be exercised concerning intelligible objects only so far as it is perfected by the intelligible species of something; and in that way it understands itself by an intelligible species, as it understands other things: for it is manifest that by knowing the intelligible object it understands also its own act of understanding, and by this act knows the intellectual faculty. But God is a pure act in the order of existence, as also in the order of intelligible objects; therefore He understands Himself through Himself.
Whether God comprehends Himself?
Objection 1: It seems that God does not comprehend Himself. For Augustine says (Octog. Tri. Quaest. xv), that "whatever comprehends itself is finite as regards itself." But God is in all ways infinite. Therefore He does not comprehend Himself.
Objection 2: If it is said that God is infinite to us, and finite to Himself, it can be urged to the contrary, that everything in God is truer than it is in us. If therefore God is finite to Himself, but infinite to us, then God is more truly finite than infinite; which is against what was laid down above ( Question [7], Article [1]). Therefore God does not comprehend Himself.
On the contrary, Augustine says (Octog. Tri. Quaest. xv), that "Everything that understands itself, comprehends itself." But God understands Himself. Therefore He comprehends Himself.
I answer that, God perfectly comprehends Himself, as can be thus proved. A thing is said to be comprehended when the end of the knowledge of it is attained, and this is accomplished when it is known as perfectly as it is knowable; as, for instance, a demonstrable proposition is comprehended when known by demonstration, not, however, when it is known by some probable reason. Now it is manifest that God knows Himself as perfectly as He is perfectly knowable. For everything is knowable according to the mode of its own actuality; since a thing is not known according as it is in potentiality, but in so far as it is in actuality, as said in Metaph. ix. Now the power of God in knowing is as great as His actuality in existing; because it is from the fact that He is in act and free from all matter and potentiality, that God is cognitive, as shown above ( Articles [1],2). Whence it is manifest that He knows Himself as much as He is knowable; and for that reason He perfectly comprehends Himself.
Reply to Objection 1: The strict meaning of "comprehension" signifies that one thing holds and includes another; and in this sense everything comprehended is finite, as also is everything included in another. But God is not said to be comprehended by Himself in this sense, as if His intellect were a faculty apart from Himself, and as if it held and included Himself; for these modes of speaking are to be taken by way of negation. But as God is said to be in Himself, forasmuch as He is not contained by anything outside of Himself; so He is said to be comprehended by Himself, forasmuch as nothing in Himself is hidden from Himself. For Augustine says (De Vid. Deum. ep. cxii), "The whole is comprehended when seen, if it is seen in such a way that nothing of it is hidden from the seer."
Reply to Objection 2: When it is said, "God is finite to Himself," this is to be understood according to a certain similitude of proportion, because He has the same relation in not exceeding His intellect, as anything finite has in not exceeding finite intellect. But God is not to be called finite to Himself in this sense, as if He understood Himself to be something finite.