While I harbor great respect for the intellect of Thomas Aquinas and rather like his philosophical methodology, no man’s reasoning is flawless. Consider the little Socratic switcheroo he pulls here on the subject of the knowledge of God.
Article 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.
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” (Romans 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.
That’s all well and good. But now consider the subsequent statements in the two following articles.
From Article 12: Since God knows not only things actual but also things possible to Himself or to created things, as shown above (Article 9), and as these must be infinite, it must be held that He knows infinite things.
From Article 13: Since as was shown above (Article 9), God knows all things; not only things actual but also things possible to Him and creature; and since some of these are future contingent to us, it follows that God knows future contingent things.
Now, where is it shown in Article 9 that “God knows all things?” It was certainly CLAIMED in Article 9 that God knows all things, to be precise, Aquinas writes, “I answer that, God knows all things whatsoever that in any way are.” But it was not SHOWN.
This is an uncharacteristic Jordan Peterson-style appeal to self-authority. But at least Aquinas did not marvel at the wisdom of his own assertion.