Book IX · 8

Among the animals which have not reason one life is distributed; but among reasonable animals one intelligent soul is distributed: just as there is one earth of all things which are of an earthly nature, and we see by one light, and breathe one air, all of us that have the faculty of vision and all that have life.

Among irrational creatures one life is distributed, and among the rational one intellectual soul has been parcelled out. Just as also there is one earth for all the things that are of the earth; and one is the light whereby we see, and one the air we all breathe that have sight and life.