I believe that there are ghosts and spirits because there is proof that people have souls (people who die continue to cognitively function despite the fact that their brain is dead). However, I still don't believe there is a god ruling over them instead they become a part of space-time itself free to do what they wish.
I don't believe in them but in saying that I don't believe that it is absolutely imposable they exist.
I really find it hard(as in almost inconceivable) to believe that if they do exist they are us after we die.
I think that when we die we are dead and to be honest I have no problem with that.