ICLE [I, Q. 14, Art. 9]

Whether God Has Knowledge of Things That Are Not?

Objection 1: It seems that God has not knowledge of things that are
not. For the knowledge of God is of true things. But "truth" and
"being" are convertible terms. Therefore the knowledge of God is not
of things that are not.

Obj. 2: Further, knowledge requires likeness between the knower and
the thing known. But those things that are not cannot have any
likeness to God, Who is very being. Therefore what is not, cannot be
known by God.

Obj. 3: Further, the knowledge of God is the cause of what is known
by Him. But it is not the cause of things that are not, because a
thing that is not, has no cause. Therefore God has no knowledge of
things that are not.

_On the contrary,_ The Apostle says: "Who . . . calleth those things
that are not as those that are" (Rom. 4:17).

_I answer that,_ God knows all things whatsoever that in any way are.
Now it is possible that things that are not absolutely, should be in a
certain sense. For things absolutely are which are actual; whereas
things which are not actual, are in the power either of God Himself or
of a creature, whether in active power, or passive; whether in power
of thought or of imagination, or of any other manner of meaning
whatsoever. Whatever therefore can be made, or thought, or said by the
creature, as also whatever He Himself can do, all are known to God,
although they are not actual. And in so far it can be said that He has
knowledge even of things that are not.

Now a certain difference is to be noted in the consideration of those
things that are not actual. For though some of them may not be in act
now, still they were, or they will be; and God is said to know all
these with the knowledge of vision: for since God's act of
understanding, which is His being, is measured by eternity; and since
eternity is without succession, comprehending all time, the present
glance of God extends over all time, and to all things which exist in
any time, as to objects present to Him. But there are other things in
God's power, or the creature's, which nevertheless are not, nor will
be, nor were; and as regards these He is said to have knowledge, not
of vision, but of simple intelligence. This is so called because the
things we see around us have distinct being outside the seer.

Reply Obj. 1: Those things that are not actual are true in so far as
they are in potentiality; for it is true that they a