Now you'll notice that I put this in the science section of these boards. And I have to tell you I certainly don't believe in an afterlife. You've got to solve your problems here on earth. You don't get a second chance. And I've been a skeptic (to varying degrees) all my life. You know some ghost stories are striking. They really are. And yes, some of the witnesses are credible, they are. I do have to tell you, I learned about a unique phenomenon in HS. When a loved one dies, the psychological need is so great, the person just naturally hallucinates. Psychiatric care is only indicated if they persist. Actually I can tell you, my mother was devastated by the loss her favorite aunt. And she kept remarking people on the street looked like her. You know, a lot of ghost stories just sound like illusions anyway, don't they? Now when my cousin's abusive father died, he saw a full corporeal form of him looking out the side window into the driveway where he was! But this brings up another point. Why are ghosts often seen wearing clothes? And glasses and sporting the haircut they died with? I hoped this would be a skeptical debate. But you know the debate wouldn't be complete without our theist friends. Thoughts? Explanations?
To borrow/paraphrase/alter a quote from Jodie Foster in the movie Contact, "If there isn't an afterlife or Heaven, seems like an awful waste of space!".
Leftover energy that has positive and negative vibes depending on the situation. A possession of their past lives keeps them around like a ball and chain. Personally, protecting with runes is nice to comfort the energy before it goes on to become something else in the next decaying biomechanical suit.
There's no such thing as haunted houses, only mental occupants. Ghosts stem from the lack of understanding how our brains interpolate fuzzy information. How we're wired by survival instincts to find faces and bodies in shadows. How our minds struggle to perceive reality when tired and transitioning into sleep and dream states.
And Don't forget sleep paralysis. That may cause symptoms resembling "ghosts" or demonic presences harassing at nighttime but it is just the brain playing dirty tricks on you.