Things that go bump in the night.....
Ancient pagan ideas abound today no less than in the past. Some folks still think there are dead people - ghosts - who hang around just to haunt their enemies and their descendants, or (in a more modern view) in bondage to some unresolved trauma or psychological conflict which somehow is seen as outliving the body of the person who had it. If so, then by now, there must be some psychologist-ghosts to help them out of it, no doubt charging them by the hour. (I hear boo-therapy is effective.) Many reported ghosts are hallucinations, but sometimes hallucinations can seem almost substantively alive, especially to those who insist that they are.
When we die, do we 'go ghost'? Is a ghost demonic? Is it really a visiting apparition from the dead? Or is it caused by a human longing to know the world beyond? I don't know. Whether or not you believe in ghosts, if they're there, I figure that ghosts believe in us.
Whether the culture is European, African, or Asian, one of the common beliefs about ghosts is that they are found in cemeteries, burial grounds, and places of mass death or murder. Poltergeists like to make noise and toss objects around as if they're throwing a childish tantrum. Japanese onryos are especially vengeful and relentless. A bhuta from India is fairly neutral, but they have terms for good and evil ghosts, too. A revenant is someone who returns from the dead as an apparition (a visual image, something you can see). A phantasm is created when one (supernatural or natural) being's mind uses extra-sensory means to put images into someone else's mind. There are so many names for spirits who show themselves : spook, specter, phantom, doppelgänger, wraith. And the general reaction, even at just hearing the words, is to have at least a touch of fear. Perhaps the best thing to do with stuff that creates fear is to have fun over them. So the kiddies in Halloween costumes and the guy with the tombstone decorations on his front lawn may have it right.
Ghosts are not the kind of being you'd expect to do anything substantive - it's against their nature. It's said by some that ghosts often try to be what they're not, but if so, they can't be successful at it, because you can see right through them.
If there really are ghosts, think of what they're going through nowadays. After a short while of passing through walls and scaring little kids, it gets to be sorta 'been there, done that'. Hanging out at the old haunts just becomes a bore that... never.... ends..... . And what of the 'doltergeists' that haunt really stupid places? The night life at cemeteries is rather, well, dead. Casper ruined their image by making them seem nicey-nice. A generation raised on Scooby Doo actually thinks it's fun to be ghost hunters. And everyone knows that no apparition looks as good as Tom Cruise. One wonders why any self-respecting ghost would make more than the briefest visit.