Simply put, we cannot know if God exists or not. Both the atheists and believers are wrong in their proclamations, and the agnostics are right. True agnostics are simply being Cartesian about it, recognizing the epistemological issues involved and the limitations of human inquiry. We do not know enough about the inner workings of the universe to make any sort of grand claim about the nature of reality and whether or not a Prime Mover exists somewhere in the background. Many people defer to naturalism — the suggestion that the universe runs according to autonomous processes — but that doesn't preclude the existence of a grand designer who set the whole thing in motion (what's called deism). And as mentioned earlier, we may live in a simulation where the hacker gods control all the variables. Or perhaps the gnostics are right and powerful beings exist in some deeper reality that we're unaware of. These aren't necessarily the omniscient, omnipotent gods of the Abrahamic traditions — but they're (hypothetically) powerful beings nonetheless. Again, these aren't scientific questions per se — they're more Platonic thought experiments that force us to confront the limits of human experience and inquiry.