Specifically, Bayesian rationality:
Rationality is a real thing. It says, “Use these formulas, from math and logic, in this way without error.” That’s fine and sure advice. But — here’s the big but — rationality is silent on what goes into the formulas. What goes in is what’s it’s all about.
There is no way to bootstrap rationality. All thought has to begin in inspiration, sometimes called intuition, of which there are many kinds, none of them rational.
That is, all rational processes begin at a non-rational starting point: a world-view, if you will, that filters which facts are relevant to the rational calculation. Different world-views accept different (and equally true!) facts as relevant, and so can arrive at widely different conclusions -- all completely rational.