The supernatural is that which is outside the universe. The universe is by definition all of that which exists. Therefore the supernatural does not exist.
It will often then be disputed that those definitions are appropriate, but without defining those terms like that, I fail to see how one could hope to claim that divine revalation is outside of the banner of science. And if it isn’t, then we are either left with a phenomenon that is better explained by delusion then a god, or something that simply needs to be studied by science.
Funny you should make an ontological argument for the non-existence of God. Most discount any ontological arguments for Him, so I’m surprised you’d go there. Also funny that you dismiss out of hand concepts like the multi-verse theory. Science is ever-changing, you know. We’re always learning. I would be careful about your ontology, if you want to be taken seriously about science.
In any event, I always thought of the universe as a sort of expanding balloon with limits (I understand that the finite vs. infinite nature of the universe is in dispute, but I believe it is the former, as the concept of expanding seems to require limits in the first place). I’d imagine that, as one on the inside of the “balloon,” it would be fairly easy to study the phenomena going on inside the balloon, but to try to make claims about what may or may not exist outside of the finite limits of the balloon would require being able to see beyond its limits. A lot easier said than done, so you’d either have to have some way of seeing outside it, or rely on the words of someone who has crossed over to the other side, or comes from there. But it takes some kind of hubris that to claim that it would be a mere delusion to say that something exists outside of it. I subscribe to the view that, if the laws of physics inside the balloon dictate that an act requires a cause, then at some point there had to be a cause acting outside those laws of physics and the causal requirement, which set those things in motion. Doesn’t have to be a personal, salvific God, necessarily, but the God necessarily has to have some traits by nature of existing outside said laws.
But really, if you want to come in here shouting Richard Dawkins’ amateurish arguments about delusion vs. revelation, I would think again. Dawkins is a brilliant evolutionary biologist, but should have quit after the blind watchmaker. He’s a terribly misinformed philosopher and quite an embarrassment to many atheist intellectualists, due to his atrocity of a God Delusion book. The fact that it was such a pop-culture hit should have been your first clue. We are a society that treasures books written by Joel Olsteen, for crying out loud. If you want to be taken seriously as an agnostic or atheist, you should really study some serious and credible sources, not pop culture booksellers.