Do you believe in ghosts?

I have never had a supernatural experience of any sort but that's hardly a basis to say such things don't exist. It's like saying since I've never seen Paris with my own eyes Paris doesn't exist. I know very credible people who say they have seen ghosts and such, and as a Catholic there is more in our teaching to argue they didn't see them as to say they did. Since our ability to understand this world and the universe (let alone God) is like asking a 6 month old baby to repair my computer, I am left saying I mostly don't believe for mostly religious reasons but the fact people I respect those who say they have puts my being sure of it at only 60 percent certainty and am not arrogant enough to disrespect someone who does believe.