Of God and His Creatures

That an Intelligence subsisting apart and a Soul are not of one Species

A DIFFERENT type of being makes a different species. But the being of the human soul and of an intelligence subsisting apart is not of one type: the body can have no share in the being of a separately subsisting intelligence, as it can have in the being of the human soul, united with the body as form with matter.

3. What makes a species by itself cannot be of the same species with that which does not make a species by itself, but is part of a species. Now a separately subsisting intelligence makes a species by itself, but a soul not, it is part of the human species.

4. The species of a thing may be gathered from the activity proper to it: for activity shows power, and that is an indication of essence. Now the proper activity of a separately subsisting intelligence and of an intelligent soul is understanding. But the mode of understanding of a separately subsisting intelligence is quite different from that of the soul. The soul understands by taking from phantasms: not so the separately subsisting intelligence, that has no bodily organs in which phantasms should be.*

2.93 : That Intelligences Subsisting apart are not more than One in the same Species
2.96 : That Intelligences Subsisting apart do not gather their Knowledge from Objects of Sense