The only thing to fear is how little we actually know.
There are scientific theories that paranormal events are products of the human mind, and ghosts only exist because we believe in them. A few years ago, a group of science students and college friends set out to prove this by creating a supernatural entity... with their minds. They attempted to recreate an experiment from the 1970s where they stare at a drawing of a dead man and try to summon his spirit.
So they got the drawing and stared and stared. And stared some more. They concentrated very hard on bringing this spirit forward. The experiment was a success—an unfortunate success.