own 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 (AA. 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 Obj. 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 Obj. 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.
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FOURTH ARTICLE [I, Q. 14, Art. 4]

Whether the Act of God's Intellect Is His Substance?

Objection 1: It seems that the act of God's intellect is not His
substance. For to understand is an operation. But an operation
signifies something proceeding from the operator. Therefore the act of
God's intellect is not His substance.

Obj. 2: Further, to understand one's act of understanding, is to
understand something that is neither great nor chiefly understood,
but secondary and accessory. If therefore God be his own act of
understanding, His act of understanding will be as when we understand
our act of understanding: and thus God's act of understanding will not
be something great.

Obj. 3: Further, every act of understanding means understanding
something. When therefore God understands Himself, if He Himself is
not distinct fro