Summa contra Gentiles1.51 Chapter LI and LII. Reasons for inquiring how there is a multitude of things understood in the divine intellect

Lest, however, from the fact that God understands many things we be led to conclude that there is composition in the divine intellect, we must examine in what way the things He understands are many.

Now they cannot be understood to be many, as though the many things God understands had a distinct being in Him. For these understood things would either be the same as the divine essence, and thus we should have multitude in the essence of God, which has been disproved above in many ways, or else they would be added to the divine essence, and thus there would be something accidental in God, and this again we have proved above to be impossible.

Nor again can it be admitted that these intelligible forms exist per se: as Plato, in order to avoid the above impossibilities, seems to have maintained by holding the existence of ideas. Because the forms of natural things cannot exist apart from matter, since neither are they understood without matter.

And even if the above supposition were admissible, it would not suffice to explain how God understands many things. For since the aforesaid forms are outside the essence of God, if God were unable without them to understand the multitude of things, as is requisite for the perfection of His intellect, it would follow that the perfection of His understanding depends on something else: and consequently the perfection also of His being, since His being is His act of intelligence: the contrary of which has been shown above.

Again. Since all that is beside His essence is caused by Him, as we shall prove further on, it must needs be that if the aforesaid forms are outside God, they are caused by Him. Now He is the cause of things by His intellect, as we shall show further on. Therefore in order that these intelligible forms may exist, it is required that previously in the order of nature God should understand them. And consequently God does not understand multitude through the fact that many intelligible things exist per se outside Him.

Again. The intelligible in act is the intellect in act, even as the sensible in act is the sense in act. But so far as the intelligible is distinct from the intellect, both are in potentiality, as appears in the senses: for neither is the sight actually seeing, nor the visible actually seen, except when the sight is informed by the species of the visible object, so that one thing results from sight and visible. Accordingly if the intelligible objects of God are outside His intellect, it will follow that His intellect is in potentiality, and likewise His intelligible objects: and thus He will need something to reduce Him to actuality. But this is impossible, since this thing would be previous to Him.

Further. The object understood must be in the intellect.

Therefore in order to explain how God understands the multitude of things it is not enough to suppose that the forms of things exist per se outside the divine intellect; but it is necessary that they be in the divine intellect itself.

1From these very same reasons it appears that it cannot be admitted that the multitude of the aforesaid intelligibles is in some other beside the divine intellect, either that of the soul, or that of an angel or intelligence. For in that case the divine intellect, in respect of one of its operations, would depend on some secondary intellect: which also is impossible.

Even as things that subsist in themselves are from God, so are those that exist in a subject. Wherefore the existence of the aforesaid intelligibles in some secondary intellect presupposes God's act of intelligence whereby He is their cause. It would also follow that God's intellect is in potentiality: since His intelligibles would not be united to Him. Even as each thing has its proper being so has it its proper operation. Wherefore it is impossible that because one intellect is disposed to operate, therefore another exercises intellectual operation, but only that same intellect Where we find the disposition: even as a thing is by its own essence and not by another's. Hence it does not become possible for the first intellect to understand multitude, through the fact that many intelligibles are in some second intellect.