You’re not arguing science and religion, you’re rejecting one religion, claiming it has no merit, and arguing your case with another one, philosophical naturalism (a “belief” that the natural world is all that exists, which has no proof either). The belief that a natural world is all that exists is not only unverified, but it is unverifiable as well... a fantasy according to your definition.
First of all, I will say that I don't subscribe to such a belief - I agree that it is an undemonstrable thing. In it, after all, is a somewhat hidden negative claim (like "the supernatural does
not exist"). Such negative claims can't be demonstrated, because the supernatural
might exist while we simply haven't found it yet.
However, I'ld say that such a belief is a lot more rational then for example the belief that the supernatural DOES exist.
For the simple reason that the natural world demonstrably exists - we are a part of it, after all.
While the supernatural isn't showing up anywhere - and humans have been trying very hard to find it for millenia now.
So, the belief of philosophical naturalism does NOT require assuming the existance of undemonstrable entities or forces.
The belief that the supernatural, for example, does exist... DOES require assuming the existance of undemonstrable entities or forces.
So right out of the gates, for that reason alone, philosophical naturalism is way more rational as opposed to theism.
But, just to make it extra clear, I don't subscribe to such a belief. I think it's a waste of time and energy to ponder over things that can't be demonstrated anyway. Yes, for all practical intents and purposes, I live my life
as if the supernatural (or any other thing that can't be demonstrated) does not exist, sure.
When I jump from a building, I fully expect to get hurt hard or killed when smacking down against the concrete. I don't assume that a supernatural entity will appear to break my fall or to stop gravity from accelerating my body by 9.81 meters per second per second (minus atmospheric resistance).
When driving on the freeway, I don't assume that an undetectable supernatural rock is blocking my way... so I don't hit my breaks for no apparant reason.
When trapped in a fire in some building, I won't assume that some angel will make the flames go away allowing me to exit unharmed.
Why would I assuming otherwise?