Just because you know a thing is true in theory, doesn't make it true in fact. The barbaric religions of primitive worlds hold not a germ of scientific fact, though they claim to explain all. Yet if one of these savages has all the logical ground for his beliefs taken away — he doesn't stop believing. He then calls his mistaken beliefs 'faith' because he knows they are right. And he knows they are right because he has faith. This is an unbreakable circle of false logic that can't be touched. In reality, it is plain mental inertia. A case of thinking 'what always was' will also 'always be.' And not wanting to blast the thinking patterns out of the old rut.

p. 151 - Deathworld (1960)