Much of what we understand nowadays in the sciences were once thought impossible or were simply unknown until we found evidence to the contrary.
There is much we still do not understand, and I am not convinced we ever will understand everything.
I'm going to be one of the "lame" rational guys that are going to post here just to say No. I'm not scared of ghosts or any supernatural beings. If I'm alone in the dark there are much bigger risks out there... Shady people in the streets, bears in the forest... (literally).
That's what I always get hung up on when it comes to the idea of consciousness. It clearly exists as a complex chemical reaction, and the best way to prove it exists is because it can be affected, it can be broken or changed. It has a real world state that can be interacted with.
Now, I'm open to that idea above, that your soul has some kind of "true" state and your tuning fork could be broken, but that seems to shut out positive modifications. If you're depressed and you take anti-depressants, and they worked (side-stepping the debate about anti-depressants, just as an example), that's when things get confusing. Is your consciousness not really depressed then? If it exists elsewhere, why does medication affect it? If your body is just a tuning fork and the medication fixes that, then...apparently you weren't "really" depressed? It starts to get really murky.
So yes, I think my mind is a result of the chemical reactions in my brain. I know some people think that cheapens life, but I actually think it improves it. It makes my life and what I make of it even more valuable, because this is it.
I do recall my grandmother telling me about her grandfather dieing and appearing before his two sisters both in two different locations telling them that his wife needed them. And sure enough when they went to her they discovered he had died at the same time that he had appeared before them.
There's also speculation that the other 98% of our dna for which we don't really know what it does could be integral to this.
It's rather interesting, now...would be nice if someone continued to do testing to see if they could indeed find another dimension like this.
Although if I wanted to play devil's advocate, some sort of low level delusion might have a place. I had a huge argument with a co-worker about self-confidence and how it works, particularly in regard to things we haven't done before. It went a bit like "Your boss just wants to know you're confident you can do the job." Me: "Well, I think I can, I think I'll be fine". "No, don't say you 'think'." "Well, I don't 'know', I haven't done it yet." "No, they want you to be confident." "I'm confident I can do it, but I don't know I can because I can't see the future, I think I can, I think I'll be fine." ... et cetera, it went on for awhile, haha. That might be more of a semantics argument but you could say confidence, at least in regards to things you haven't done before, could be a kind of self-delusion that has a good outcome. Of course, it also leads to people confidently saying they can do something, and then crashing and burning.
I'm not even arguing, I agree with you, heh, just something that occured to me, throwing that out there.
I believe "ghosts" and "spirits" are simply hallucinations, tricks of the light and other phenomena that the witness simply misunderstood and did not see properly. The brain is easily fooled after all, and there's no decent evidence to say such things exist.
I am a skeptic, I do not believe in things that cannot be confirmed through the senses.
---------- Post added 2012-07-29 at 12:03 AM ----------
The best way I think to approach ghosts, spirits, demons, poltergeists, whatever you wanna call them, is to simply acknowledge that there is no conclusive proof to suggest that they exist. That's not to say that they don't, but that we can't test or measure whether or not they do. It's like the God fallacy, you can neither prove they exist or don't exist, which is no good reason to believe that they do. I've never had an encounter with something I didn't understand or recognise and think "Must have been a ghost." I have had some bizarre experiences, working night shift at a hotel entails just that, but each time I just dismissed it as something I have no explanation for. It doesn't bother me that I can't explain weird occurrences, so long as there isn't anything for me to worry about - and there has never been any suggestion that there is - I just put it out of my mind.
Barry Gibb haunts my stereo. When I close the drawer empty, the machine 'finds' a BeeGees album and plays Stayin' Alive.
I have taken the unit apart and there's no CD lodged in there. Sony are equally confused, but they offered me an exorcism under warranty.
Sleep paralysis and similar things are extremely common.
I still get, and it's hard not to just laugh it off as nothing... even though I know it's nothing.
The most successful tyranny is not the one that uses force to assure uniformity but the one that removes the awareness of other possibilities.