Earlier quoted context omitted.
Who says folks believed myths to be realistic? We are actually talking about knowledge, not believe. There may have been many people for whom between horses and steam engine powered trains there was no certainty nor prospect for motorization, only wet dreams of flying. Interesting fact nontheless, Pegasus comes to mind.
True. I find it hard to relate to. Do priest believe god is real, (if so: also realistic,) or do they just believe in him?
What does that have to do with UX cliches? If you'd ask priests whether god is dead, they'd say, "why, horses are good enough"?!