Yes and no, I have never seen one but I do believe there are things on earth that we simply cannot see/explain, if you call that a ghost or not I'm not sure. =P
A few years ago I was staying in a hotel for one of my brothers hockey tournaments, and one of his friends saw something that was "not a person, and not an animal". The guy working there said that kind of thing happens a lot at that hotel. So yes, I believe in ghosts.
Not sure. I've seen things I can't explain. But I'm not going to just say that I knew it was a ghost. I had a pretty wild imagination as a young teen. 14 years old. My father owned this really old house that was built in 1818. He had it remodeled somewhat.
I saw this woman in really old fashioned dress one evening around 6pm walk past me as if she were there. My father was out late I remember. I was very curious...so I followed her half way before realizing she had disappeared into the guest rooms. So I stood there outside the guest room and asked if she could come out. No answer, no one had really been there. I never told anyone about it really. I was 14. Young and naive.
Can't say that I believe in "ghosts." But, I'd be dumb if I said that spiritual beings don't exist. I remain optimistic about them and if I ever encounter one, I'll be sure to let you know.
I believe that there are beings that aren't physically here like us humans, and can manifest themselves depending on the situation, but I don't know if I would label them as ghosts, since I consider ghosts as beings who are in limbo, and who aren't there to help you out somehow.