Hi everyone,

Granting the validity of some theistic proof, the typical contemporary answer against the charge of polytheism is to appeal to parsimony: why invoke more than one God when one God will do the job? There are other ways of arguing that God is unique, of course, and Aquinas' metaphysical framework allows for many diverse arguments, in the context of his proofs for God's existence.

I'd like to present two arguments for monotheism that I think stand independently of whether a skeptic will accept any of Aquinas' five ways, and thus they can be used to implement non-thomistic proofs for God's existence, such as the KCA, or Leibniz' contingency argument, or what have you.

Argument 1:

1) To be God is to have a certain nature or essence, such that if there were many "Gods", this nature would belong to them equally.
2) But to speak of a multiplicity of "Gods" is to admit difference between them, and difference is always a matter of inequality. This means that some perfections would belong more to one God than another (such as power, knowledge, exemplarity, and so on).
3) But where some perfection X belongs more to one A than to B, then the fact that B does not possess X in the greater sense that A does entails that X does not belong to B of its own nature or essence, but through some outside cause.
4) Hence, any "God" who has any perfection to a lesser degree than another would be caused in some sense, and therefore not be "God" in the first place.
5) And because this process of elimination will always exist so long as there is more than one God (since difference implies inequality)
6) there can only be one God.

Argument 2:

1. God exists. [assumption]
2. God is that-than-which-no-greater-can-be-thought. If you can think of something greater than God, then *that* is what is meant by God. [this is only a *cognitive* claim; since we are assuming the existence of God as the valid conclusion of some theistic proof, there is no further resemblance to Anselm’s ontological argument]
3.  If more than one God existed, there would have to be some way of individuating one from another.
4.  The only way of individuating one from another is by reference to something one has that the other lacks.
5.  But to admit that one or more of them lack something is to admit that there is a greater that can be thought.
6.  So, there can only be one God.

Thoughts?