 (2) According to this theory, the human soul is constituted by three substantial forms (tribus formis substancialibus) which differ essentially from one another; of these, two (vegetative and sensitive) are the result of the work of nature (opus nature)—by means of the potencies of elements and the original principles with which the matter of transmutable things is naturally endowed—and the intellective form is the result of divine creation. The three forms are present at the same time in the human embryo only after the intellective soul has been created and infused into the developing being, not before—and this is due to the need for an appropriate level of material organization that disposes the being to receive the intellective soul as its perfection (E 5, 44).