rational naturalism is impossible!

[Rational AKD]

It would be, if the false beliefs were harmful.

See, there's a reason children are more liable to believe authority figures when they're young; that's evolution in action. Parents teach their children things that are important; in an older, tribal civilization where this would be more useful, then fire being hot, and that animal being dangerous, would be true beliefs necessary for survival. Children that are more likely to accept this demonstrably true thing don't get burned or murdered by animals quite as much, while those that reject those true beliefs get killed.

Truth is all there is, and insofar as it regards the physical world that we inhabit, having a grasp on what's true is crucial for surviving. You can't believe a predator out of attacking you, for example.

you seem to forget the point I was trying to make in the OP. rational belief in naturalism is impossible. as you said, the only reason to believe any of our beliefs are necessarily true is if it is necessary to our survival. most beliefs aren't. and in fact, it's been shown that mild paranoia is more beneficial to survival than what's necessarily true. in that case, for all we know, many of our beliefs are a paranoid delusion. this includes the belief in naturalism itself, making it impossible to rationally believe it due to its self refuting nature. at best, you can say there's a 50/50 chance it's true which not only doesn't rationalize belief in it, but makes it literally impossible to rationalize because it refutes itself. you can't believe in naturalism and believe it to be true after accepting the conclusion of this argument.