The soul is not of the Substance of God, but is created. For the soul is in potentia and receives knowledge from things; it has, moreover, diverse faculties, both of which are repugnant to Divinity. For God is Pure Actuality, receives nothing from elsewhere, and is wholly simple.
Error on this subject arose from a belief that everything was corporeal, and that consequently God was the Principle of all bodies: to which the Manichaeans added that light was in some manner Divine and the world-soul; not separate from bodies but the form of the body. Thus they failed to recognize the intellect as belonging to an order of spiritual substances; from which the error began.
Nor can the rational soul have been made except by creation, since it has being apart from pre-existing matter. It is therefore a substance, the property of which is being: - for it is not substance but accident when anything exists after a certain mode, as, e.g. whiteness, which causes something to be white. And since the soul is a subsistent form, not made of corporeal matter because not a body, neither is it made of spiritual matter; from which it would follow that spiritual substances might be changed, one into another. We conclude, therefore, that the soul was made immediately by God; not by transmutation, nor from the latent virtue of matter, but by creation; for, as has been already seen, only God can create, since the first agent alone acts where nothing is presupposed. Moreover, the soul was created along with the body, although Origen erroneously believed all souls to have been created along with the angels. Augustine also says, though not positively, that the soul of the first man was produced along with the angels, and the body according to a causal conception: which may be tolerated provided the opinion be true which ascribed to the soul a nature complete in itself, not united to the body as form, but only as administering it. If the soul be united to the body as form, it is impossible; for the soul is part of human nature, and God instituted things in a perfect state which requires that a part be with its whole; whereas the soul is not perfect except as united to the body.
The opinion of Augustine may also be maintained that the soul as part of the work of the Six Days took precedence according to a certain conception of genus, inasmuch as the soul shares in the intellectual nature of the angels: it was, however, created along with the body.
- text taken from Compendium of the Summa Theologica of Saint Thomas Aquinas, by Bishop Berardus Bongiovanni