Metaphysical Thoughts: Part 2, Chapter 2.
Concerning the Unity of God.
We have often wondered at the futile arguments by which some have
sought to establish the unity of God. For example, such as the following:
"If one being is able to create the world, more than one would be
superfluous; and, if all things work toward some end, they must
have a common source." Other similar arguments might be mentioned
where proof is sought from relative or extrinsic elements. Since
such ideas are sometimes held, we shall, in the following order,
and as clearly and as briefly possible, give our demonstration.
Among the attributes of God we enumerate perfect knowledge, and
add that His perfection all arises from His own being. But if you
say that there are many Gods or perfect beings, all of them must be
omniscient. It would not be sufficient for each one merely to
know himself. For as each is omniscient he must
understand all other beings as well as himself. From which it would
follow that the omniscience of each depends
partly upon himself and partly upon another. Therefore such a being
would not be absolutely perfect. That is, God
would not be a being who derives all of his perfection from Himself.
But we have already shown that God is in every
way perfect and that He exists by virtue of His own power. From
which we conclude that God is one being. For if
there were many gods it would follow that the absolutely perfect
being would have an imperfection, which is absurd.
So much concerning the unity of God.