There is no empirical proof, but there is plenty of evidence in the form of video, photograph, and voice phenomenon. But being that they are largely unrepeatable, that evidence isn’t considered valid. But its there and unexplainable(weeding out the for sure fakes, the questionable fakes, and the like). I know that my ghost experiences are definitely not a product of my own psyche, mainly because how could I describe ghost people I saw when I was a kid that were wearing what they were in the only photograph of them ever taken, and I had never seen said photograph. I couldnt just make it up and I never had been to Oklahoma where the photograph was stored at. They were my great great grandparents from the 1800s and I had never heard of them prior to my sighting. I cant explain it other than ghosts.