There are a lot of unexplained things out there, and many people have made careers after chasing after ghosts in various ways (for television programs, for novels and books in general, and for scamming purposes)... but do I personally believe in ghosts? I'm not quite sure. I know I believe in
something.
I think it's far more likely that in the case of those "ghostly apparitions" they were real and not just figments of people's imagination, but I
don't mean spirits. Let me explain: Instead of being the spirits of the dead, I believe that it might have to do with that old dimensional theory. That theory being that the dimensions are layers upon layers, and that when people see a ghost it may just be us getting a glimpse of people on another plain of reality. Of course there's no real proof to back this up, but I prefer that explanation to the whole evil spirit bit.
P.S. - I'm tired, so a lot of what I just said may not be as detailed or coherent as I'd like.