WHY SOULS TAKE ON DIFFERENT KINDS OF BODIES.
Souls do not always descend equally; they descend sometimes lower, sometimes less low, but always in the same kind of beings (among living beings). Each soul enters into the body prepared to receive her, which corresponds to the nature to which the soul has become assimilated by its disposition; for, according as the soul has become similar to the nature of a man or of a brute, she enters into a corresponding body.