The theory on ghosts can vary on many things. From religion, to science, then to about anything. In my opinion, I follow religion. However, I don't look into it much. I personally think that ghosts can exist, but only among people who really believe in them. Now with some more thought into it, I do with God. I believe that he is among us and that he watches over us. Even though some things can go wrong. Back to the topic, it is your choice to decide whether or not they do exist. People can come up with stories about ghosts. They can also make videos with special effects to make it seem as if ghosts are real. It just depends on how you look at the entire situation. Hope this helped.