I do believe that ghosts exist due to the many instances of unexplained phenomena occurring in this world. When something can’t be explain scientifically, then there must be another explanation. There are paranormal scientists who have machines to detect ghosts. There have been some cases where a camera took a picture of something and a being is shown in the picture that wasn’t there.
Of course, the picture could have been photoshopped or something could have happened to the film, but it could also have been a ghost. Other instances of ghosts could only be explained by the presence of a ghost and nothing else. People have claimed they have witnessed ghosts and sounds in their houses when no one else was there.