20. ESSENCES ARE INTRINSICALLY POSSIBLE, NOT BECAUSE GOD CAN MAKE THEM EXIST ACTUALLY; NOR YET BECAUSE HE FREELY WILLS THEM TO BE POSSIBLE; NOR BECAUSE HE UNDERSTANDS THEM AS POSSIBLE; BUT BECAUSE THEY ARE MODES IN WHICH THE DIVINE ESSENCE IS IMITABLE _ad extra_.—(_a_) The ultimate source of the _extrinsic_ possibility of all contingent realities is the Divine Omnipotence: just as the proximate source of the extrinsic possibility of a statue is the power of the sculptor to educe it from the block of wood or marble. But just as the power of the sculptor presupposes the _intrinsic_ possibility of the statue, so does the Divine Omnipotence presuppose the intrinsic possibility of all possible things. It is not, as William of Ockam († 1347), a scholastic of the decadent period, erroneously thought, because God can create things that such things are intrinsically possible, but rather because they are intrinsically possible He can create them. (_b_) Not less erroneous is the _voluntarist_ theory of Descartes, according to which possible essences are intrinsically possible because God freely willed them to be possible.(108) The _actuality_ of all created things depends, of course, on the free will of God to create them; but that possible essences are what they are, and are related to each other necessarily as they are, because God has willed them to be such, is absolutely incredible. Descartes seems to have been betrayed into this strange error by a false notion of what is requisite for the absolute freedom and independence of the Divine Will: as if this demanded that God should be free to will, _e.g._ that two _plus_ two be five, or that the radii of a circle be unequal, or that creatures be independent of Himself, or that blasphemy be a virtuous act! The intrinsic possibility of essences is _not_ dependent on the Free Will of God; the actualization of possible essences is; but God can will to actualize only such essences as He sees, from comprehending His own Divine Essence, to be intrinsically possible. But it derogates in no way from the supremacy of the Divine Will to conceive its free volition as thus consequent on, and illumined by, the Divine Knowledge; whereas it is incompatible with the wisdom and sanctity of God, as well as inconceivable to the human mind, that the necessary laws of thought and being—such as the principles of contradiction and identity, the principle of causality, the first principles of the moral order—should be what they are simply because God has freely willed them to be so, and might therefore have been otherwise.