Thomas Aquinas

“ I answer that, Some have held that angels, acting by the power of God, produce rational souls. But this is quite impossible, and is against faith. For it has been proved that the rational soul cannot be produced except by creation. Now, God alone can create; for the first agent alone can act without presupposing the existence of anything ”

“ For those who first began to observe the nature of things, being unable to rise above their imagination, supposed that nothing but bodies existed. Therefore they said that God was a body, which they considered to be the principle of other bodies. And since they held that the soul was of the same nature as that body which they regarded as the first principle, as is stated De Anima i, 2, it followed that the soul was of the nature of God Himself. ”

“ Therefore everything else acts by producing a change, whereas God alone acts by creation. Since, therefore, the rational soul cannot be produced by a change in matter, it cannot be produced, save immediately by God. ”

“ But spiritual substances are much more perfect than corporeal. Therefore, since bodies produce their like in their own species, much more are angels able to produce something specifically inferior to themselves; and such is the rational soul. ”

“ But man is like to God in his soul. Therefore the soul was created.
I answer that, The rational soul can be made only by creation; which, however, is not true of other forms. The reason is because, since to be made is the way to existence, a thing must be made in such a way as is suitable to its mode of existence. Now that properly exists which itself has existence; as it were, subsisting in its own existence. Wherefore only substances are properly and truly called beings ”

“ That which differs, properly speaking, differs in something; wherefore we seek for difference where we find also resemblance. For this reason things which differ must in some way be compound; since they differ in something, and in something resemble each other. ”