De Moor IV:23: Arguments for the Simplicity of God: A Priori
Simplicity follows, which again is a more Negative term, since one calls that Simple which is without composition; Positively it is called Unity, that is, the altogether perfect Unity of the Divine Essence and Attributes, excluding all Real Composition. The Unity of Essence is declared, α. by Sacred Scripture both positively and negatively, in the passages cited by our AUTHOR. β. Reason also demonstrates the same,
1. A priori, a. From Consummate Perfection. For, if you set up multiple Gods, you will not be able to conceive of them all as consummately perfect at the same time. Take the Gods Jupiter, Neptune, and Apollo. It is desirable to know, whether Jupiter contains the same perfections in number as Neptune contains, or not? If you answer in the negative, you are certainly not acknowledging Jove as consummately perfect; since outside of him there are other perfections, and those infinite, in Neptune, which perfections Jupiter does not enjoy. But outside of the infinite another infinite perfection is not able to be granted or to be conceived; neither is one consummately perfect that is not infinitely perfect. It will be necessary, therefore, that Jupiter, if he be God, contain in himself absolutely all true perfections without any imperfection adhering, and so also those perfections that belong to Neptune. But how will that be possible? Only if, either with Neptune the Deity is the same in number, and so not two: or Jupiter as the cause comprehends in himself the perfections of Neptune, and communicates them to Neptune. But by this is plainly destroyed, as much Neptune’s Independence, as his Deity. And so two infinitely perfect Beings are complete contradictories.
b. From Independence, whereby God is sufficient unto Himself, and is the supreme cause of all things outside of Himself, which all accordingly depend upon Him, and are under His government. But if all things depend upon One Independent God, multiple Deities are not able to be granted, unless one Deity also depend upon another; but a dependent God is not God.
c. From Omnipotence and Omniscience, which Perfections are not at all among the last of Infinitely Perfect Deity: but you are not able to conceive of multiple Gods that enjoy both of these Perfections. For, if there be multiple Gods, one could keep his thoughts concealed, so that they might be hidden from the other, or not. But if he should prevail to do this, all are not Omniscient; but if not, all are not Omnipotent. One perhaps might will to create the world, the other not: the latter could impede the execution of this intention of the former, or not: if not, he would not be Omnipotent; but if indeed, the former would lack Omnipotence.