Scientific Explanation Ghosts- The most widely accepted theory about the "feelings" of being watched, unexplained dread, chills etc. It has to do with something called infrasound. Infrasound is sound that registers just below our hearing levels, and when we hear it, induces very bad feelings. The explanation for this may be in our evolution. Certain animals, such as tigers, make noises in that frequency. Therefore, after being eaten by tigers for millinenia, we have come to know anything within that sound frequency should make us run, so we dont die.
Scientific Explanations for Demon Posession-Demon possesion can be potentially attributed to many different causes. Most attribute it to a long list of one or more mental illnesses, such as tourettes, epilepsy, schizophrenia, and multiple personality disorder. A leading reason that people believe this is that people seem to being posessed less and less as time and medical treatment goes on.
Scientific Explanation for Deja Vu- Deja Vu is one of the more common strange experiences. Deja Vu is the sense that one has done something before. There are several explanations for it including chemical imbalances, misfirings of the brain, and epilepsy.
Whehter you believe in the supernatural or not, these are possible explanatins for things that are unknown.