Thank you for your question. The nature of hypothesizing is such that many things are hypothetically possible. However, the proofs for the existence of God, based on causality or on the nature of possibility and necessity are such that they only prove the existence of one first cause or one necessary being. In order to posit more than one God, there would need to be proof of that.
If the existence of God is derived from an inductive proof that there is order in the universe, then unless some Attributes of God are presupposed, the limitation of such an argument is that while it establishes the existence of a powerful, intelligent being, it does not prove that that being is One. Islamic philosophers do not seek to establish that from this proof either. But by the same token, it also doesn't establish more than one being and so that would have to be supposed. What it argues for is at least one being. However, what is misunderstood here is the conception of what is meant by the Oneness of God and assuming that it is numerical oneness rather than the lack of any limitation.
The Oneness of God is established through our conception of Him, and this is derived from the scriptural sources that describe Him as without limitations such that even the conception of a second is not possible. This method of argumentation is perfectly acceptable and is why the philosophy of religion discusses the conception of God before His existence as it is important to first know what is being established. In this sense, if God is unlimited, it is logically impossible for there to be two or more gods and that would contradict the concept of an unlimited Being.
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