infrared light
ultra violet light
magnetic fields
microwaves
all radio waves
sonar
sound waves
etc.
we can't see these with our human eyes. yet we all accept them. because science told us it was true. but science only told us this within the last 200 years. these things ALWAYS existed. we just couldn't see it until science told us it was there.
now scientists are finding life forms that exist only in the infrared spectrum. we didn't know they were there until camera's started taking pictures of them. so soon science will tell us there are creatures in other wavelengths or whatever they explain it.
the point is, just because YOU can't see it, doesn't mean it's not still out there. and until YOU can prove it doesn't exist, YOU look foolish for saying it doesn't.
and since nobody can prove it either way, we should all shut up.
ancient civilizations seemed to have the same reoccuring problem with the spirit realm that we do today in modern society.