I generally believe that the universe is so big and time so vast that obviously there are going to be plenty of things that can happen that don't happen regularly on any scale we tend to acknowledge... and so I try not to just write off an observation as someone being obviously mistaken because what they say happened would be considered "impossible". There are plenty of rare natural occurances that I will never see, no matter how much I might like to observe them (from ball lightning to St. Elmo's fire to green flashes at dawn and so on) that I have to leave room that there might really be something going on with ghost stories.

That said, I'm highly skeptical, especially of a regularly accepted definition of a 'ghost' being the cause of the many ghost sighting claims. Setting aside hoaxes, most ghost photos I've seen are highly laughable... people really wishing to see a ghost in the photo where I only see a dust spec reflected in the camera lens, or the camera's wrist strap dangling in the shot and lit by the flash. Surely the vast majority of ghost claims are from people worked up to the point where they see what they want to see, and disregard a much more natural explanation.

People are psychologically prone to seeing patterns (and hence, a "presence") behind random occurrences, and shifting mental states going into and coming out of sleep (as well as when awake and yet tired) can contribute to fear and paranoia. Being scared of a predator creeping up on you while you sleep is an instinctual survival mechanism that helped keep humans alert and alive before we had so thoroughly conquered the world around us and turned it into suburbia... it has hung on even though actual dangers have greatly decreased. All of this adds up to priming us to be scared at night, and to look for a predator hidden in our surroundings. Beyond that, we know the brain is capable of creating realistic hallucinations for us, and surely there's the possibility that in rare situations there's a misfire in a person's mind... something that's not likely to repeat, or a sign of madness or anything severe, but enough to convince them they've experienced something unreal.

So with this in mind, I tend not to believe in ghosts, but I do leave room for the idea that something may be happening that people are observing, even if I find the narrative they attribute to the event highly dubious. Could it be possible to see an echo of the past? See a person in a chair, or walking down a hall who isn't there currently? Possibly. Look at all the tricks we manage to coax out of natural processes we can readily understand and manipulate. This writing you are reading that doesn't exist in any real physical sense... but we found ways to transmit energy, shape it and get this result. Is it completely impossible that natural reactions are occurring, more rarely surely, but just often enough to be observed... something more complex than the reflection of an image in the surface of a pond, but really no more sinister?

And finally, I'll be the first to admit that, no matter how rational I may like to be, I can easily freak myself out. I've got an active imagination, as do most people here I'm sure, and if it starts going off on faces in mirrors and frights leaping out at me from the darkness, I'm not going to want to go poking around the creepy abandoned house at night. Sure, that place isn't *really* haunted... but I think I'd stay where it's light and safe just the same.