In all my life I have met only one person who claims to have seen a ghost. And the interesting thing about the story is that that person disbelieved in the immortal soul before she saw the ghost and still disbelieves after seeing it. She says that what she saw must have been an illusion or a trick of the nerves. And obviously she may be right. Seeing is not believing.
Unlike C. S. Lewis, I’ve never met anyone who’s seen a ghost. I don’t automatically believe ghost stories. But I don’t automatically disbelieve them, either. Nor do I reflexively write off stories of possessions, visions, miracles or other creepy stories of the paranormal.
Context is everything. I can disbelieve in orcs because I know J. R. R. Tolkien made them up for his epic universe. I can disbelieve in Martians because we know Mars to be inhospitable to all but the simplest organic life. I can disbelieve in the Flying Spaghetti Monster because it was some wiseass college kid’s attempt to poke fun at religious beliefs while questioning the need to present intelligent design in school curricula.
But we have no such context of knowledge which makes ghosts or demons inherently impossible … or even unlikely.