(CG 1/051). Some Discussion of the Question how there is in the Divine Unde... (Book 1: Of God As He Is In Himself) (Summa Contra Gentiles) (Aquinas, Thomas, St.)

IT is not to be supposed that the multitude of intelligible ideal forms is in any other understanding save the divine, say, the understanding of an angel. For in that case the divine understanding would depend, at least for some portion of its activity, upon some secondary intellect, which is impossible: for as substances are of God, so also all that is in substances: hence for the being of any of these forms in any secondary intellect there is prerequired an act of the divine intelligence, whereby God is cause.

2. It is impossible for one intellect to perform an intellectual operation by virtue of another intellect being disposed to that operation: that intellect itself must operate, which is disposed so to do. The fact then of many intelligible forms being in some secondary intellect cannot account for the prime intellect knowing the multitude of such forms.