I've decided that I'm not going to believe in ghosts. Why? Well the reason is pretty simple.
Every kid is taught that ghosts say "boo!" Who decided this? It's become unanimous. According to our culture and accepted norms - ghosts say "boo". But why would your spirit in death be saying something you never said in life? When was the last time you said "boo"? Were you impersonating a ghost?
The only explanation is that nobody has ever spoken with a ghost. And that must be because they don't exist. Logic.
As an aside - I think it would be funny if someone re-cut the movie Ghost so that Patrick Swayze's dialog after he dies is replaced by someone just repeating "boo!" over and over.