An acquaintance and myself have been arguing about the existence of universals. His argument is that a universal, such as the number two, is an abstract concept, but must be accounted for somehow. He asks where the number two is. (I consider that a nonsense question.) He believes this number two must exist in some nonmaterial realm. If the number two exists, he says, as it does in mathematics, then it must be somewhere. From this he concludes that philosophical naturalism/materialism is incorrect, thus opening up the possibility of the existence of a supreme being.
I have made many posts explaining why I disagree with his ideas, but he refuses to budge on this matter. I cannot reproduce the posts here because it came from a private forum.
Now on to the question of gods. He argues that it is nonsensical to ask for scientific evidence of a god because science deals with the material realm, and he believes the god is non-material (whatever the hell that means). Because science deals with the material realm, it is illogical to search for evidence for or against the existence of a supreme being; rather, that question must be determined by philosophical proofs in much the same way we have mathematical proofs.
What are your thoughts on the problem of universals? Is it nonsensical to look for scientific evidence of a non-material god? Can philosophical proofs "prove" a god's existence?