Even within the perspective of religious philosophy, the existence of ghosts in the sense of a spirit that stays on Earth and causes noticeable effects is difficult. Mainly- ghosts would not be made of matter, but could interact with matter. Within the realm of religious philosophy there are all sorts of explanations for the “mundane” version of this question of how a spirit attaches itself to the matter of the body in the first place, but all of those explanations kind of go out the window when the spirit sticks around and starts interacting with other matter. If ghosts only appear in sensory visions and do not truly interact with matter (I believe this was the view of Aquinas), then you have a major problem in proof and then ghosts effectively do not exist for practical purposes. The Catholic Church believes that the dead can appear to the living in visions but takes no stance on physical manifestations.

Within science, of course, there has never been a scientific observation of any supernatural being such as a ghost or effects it might have. But that doesn’t disprove the idea of purely spiritual apparitions. Then again, it also doesn’t disprove that Zorlon the Gorilla God appeared to me in a dream either. I think we can pretty conclusively say that you can live your life under the assumption that ghosts don’t exist and be completely 100% fine.