(CG 2/65). That the Soul is not a Body (Book 2: God The Origin of Creatures) (Summa Contra Gentiles) (Aquinas, Thomas, St.)

SENSE is found in all animals, but animals other than man have no intellect: which is proved by this, that they do not work, like intellectual agents, in diverse and opposite ways, but just as nature moves them fixed and uniform specific activities, as every swallow builds its nest in the same way.

2. Sense is cognisant only of singulars, but intellect is cognisant of universals.

3. Sensory knowledge extends only to bodily things, but intellect takes cognisance of things incorporeal, as wisdom, truth, and the relations between objects.

4. No sense has reflex knowledge of itself and its own activity: the sight does not see itself, nor see that it sees. But intellect is cognisant of itself, and knows that it understands.