Did you ever encounter ghosts, spirits or whatever you call them during your camping trips? I myself don't believe in ghosts. I think they exist only in our mind. But, just because I don't believe them doesn't mean they don't really exist.
I don't know that I would say I believe in ghosts or what have you but yes I do believe there are other things in this world that we cannot see. Whatever they may be, they haven't bothered me when camping.
Most ghosts actually exist only in our mind, but I agree with HillBillyMama, there are things we cannot see or perceive using the other sensory organs. I am glad I never encountered one during my camping days.