Objection 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.
Objection 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 to Objection 1: Those things that are not actual are true in so far as they are in potentiality; for it is true that they are in potentiality; and as such they are known by God.
Reply to Objection 2: Since God is very being everything is, in so far as it participates in the likeness of God; as everything is hot in so far as it participates in heat. So, things in potentiality are known by God, although they are not in act.
Reply to Objection 3: The knowledge of God, joined to His will is the cause of things. Hence it is not necessary that what ever God knows, is, or was, or will be; but only is this necessary as regards what He wills to be, or permits to be. Further, it is in the knowledge of God not that they be, but that they be possible.
Whether God knows evil things?
Objection 1: It seems that God does not know evil things. For the Philosopher (De Anima iii) says that the intellect which is not in potentiality does not know privation. But "evil is the privation of good," as Augustine says (Confess. iii, 7). Therefore, as the intellect of God is never in potentiality, but is always in act, as is clear from the foregoing (A[2] ), it seems that God does not know evil things.
Objection 2: Further, all knowledge is either the cause of the thing known, or is caused by it. But the knowledge of God is not the cause of evil, nor is it caused by evil. Therefore God does not know evil things.
Objection 3: Further, everything known is known either by its likeness, or by its opposite. But whatever God knows, He knows through His essence, as is clear from the foregoing (A[5]). Now the divine essence neither is the likeness of evil, nor is evil contrary to it; for to the divine essence there is no contrary, as Augustine says (De Civ. Dei xii). Therefore God does not know evil things.
Objection 4: Further, what is known through another and not through itself, is imperfectly known. But evil is not known by God; for the thing known must be in the knower. Therefore if evil is known through another, namely, through good, it would be known by Him imperfectly; which cannot be, for the knowledge of God is not imperfect. Therefore God does not know evil things.
On the contrary, It is written ( Prov. 15:11 ), "Hell and destruction are before God [Vulg: 'the Lord']."
I answer that, Whoever knows a thing perfectly, must know all that can be accidental to it. Now there are some good things to which corruption by evil may be accidental. Hence God would not know good things perfectly, unless He also knew evil things. Now a thing is knowable in the degree in which it is; hence since this is the essence of evil that it is the privation of good, by the fact that God knows good things, He knows evil things also; as by light is known darkness. Hence Dionysius says (Div. Nom. vii): "God through Himself receives the vision of darkness, not otherwise seeing darkness except through light."
Reply to Objection 1: The saying of the Philosopher must be understood as meaning that the intellect which is not in potentiality, does not know privation by privation existing in it; and this agrees with what he said previously, that a point and every indivisible thing are known by privation of division. This is because simple and indivisible forms are in our intellect not actually, but only potentially; for were they actually in our intellect, they would not be known by privation. It is thus that simple things are known by separate substances. God therefore knows evil, not by privation existing in Himself, but by the opposite good.
Reply to Objection 2: The knowledge of God is not the cause of evil; but is the cause of the good whereby evil is known.
Reply to Objection 3: Although evil is not opposed to the divine essence, which is not corruptible by evil; it is opposed to the effects of God, which He knows by His essence; and knowing them, He knows the opposite evils.
Reply to Objection 4: To know a thing by something else only, belongs to imperfect knowledge, if that thing is of itself knowable; but evil is not of itself knowable, forasmuch as the very nature of evil means the privation of good; therefore evil can neither be defined nor known except by good.
Whether God knows singular things?
Objection 1: It seems that God does not know singular things. For the divine intellect is more immaterial than the human intellect. Now the human intellect by reason of its immateriality does not know singular things; but as the Philosopher says (De Anima ii), "reason has to do with universals, sense with singular things." Therefore God does not know singular things.
Objection 2: Further, in us those faculties alone know the singular, which receive the species not abstracted from material conditions. But in God things are in the highest degree abstracted from all materiality. Therefore God does not know singular things.
Objection 3: Further, all knowledge comes about through the medium of some likeness. But the likeness of singular things in so far as they are singular, does not seem to be in God; for the principle of singularity is matter, which, since it is in potentiality only, is altogether unlike God, Who is pure act. Therefore God cannot know singular things.
On the contrary, It is written ( Prov. 16:2 ), "All the ways of a man are open to His eyes."
I answer that, God knows singular things. For all perfections found in creatures pre-exist in God in a higher way, as is clear from the foregoing (Q[4], A[2]). Now to know singular things is part of our perfection. Hence God must know singular things. Even the Philosopher considers it incongruous that anything known by us should be unknown to God; and thus against Empedocles he argues (De Anima i and Metaph. iii) that God would be most ignorant if He did not know discord. Now the perfections which are divided among inferior beings, exist simply and unitedly in God; hence, although by one faculty we know the universal and immaterial, and by another we know singular and material things, nevertheless God knows both by His simple intellect.