As the thread started with a reference to Prof. Brian Cox's pronouncement that ghosts don't exist, relying on his physics background to reach this conclusion...
Many people, from many cultures, over thousands of years, have believed in ghosts of one sort or another. In many cases, the belief has been so strong that it has led to societal behaviour that most of us would consider extreme or bizarre, designed to ward off or propitiate the ghosts.
For comparison (Spoiler): Santa Claus does not exist in a literal sense. However, the idea of Santa directly affects the behaviour of children, so Santa Claus is a real phenomenon.
In the modern western world, our concept of the ghost has been influenced by the common tropes of fiction. Just as the vampire or werewolf now seem to fit a standard formula, the ghost is typically portrayed as haunting a place where they suffered or died, and often seeking either revenge or some other form of release.
Bram Stoker's Dracula was in many ways different from the vampires of folklore and legend, and was equally different from the suave and handsome Count of many later adaptations. The werewolf of folklore and legend was not governed by the full moon or only vulnerable to the silver bullet as it is always portrayed now. Zombies in every zombie apocalypse film share many characteristics that were not associated with the zombie of Haitian voodoo.
And similarly, the ghosts of folklore were very different from the ghosts of modern fiction.
So if you want to decide whether you believe in ghosts, your first question perhaps should be, "What do I mean by a ghost?"
Is "a ghost" one phenomenon, or are there several phenomena, all given the same general name?
For example,
just three of the many common concepts of the ghosts (I hesitate to dignify them with the name of "theories") are:
- The soul of a dead person, remaining on Earth, and somehow still able to act purposefully.
- The so-called "stone tape theory": the idea that stones, or stone buildings, can somehow record and replay the images or sounds of events in a manner that is analogous to old-style magnetic tape.
- Some form of repeated shared hallucination, in which some physical aspect of a location (e.g. background ultrasound) triggers similar reactions in different people on different occasions.
Plan A: You could consider which concept of the ghost requires you to make the smallest number of "assumptions" that are not yet supported by scientific orthodoxy, and which one you consider to be most plausible or least implausible. That would give you a subjective reason to believe or not believe.
Plan B: Alternatively, you could consider the various possible explanations from the point of view of what sort of evidence would support or disprove them, and consider what experiments could be done to test and refine the hypothesis. (A logical positivist would argue that if no such experiment could be conceived, even in principle, then the question would be meaningless.)
Of course, in real life, most of us do not have the expertise or the facilities to set up such experiments, and we know that funding for formal scientific research into the subject will never be available in respectable academia. This is why most people resort to Plan A.
Personally, I do not believe in ghosts — there are too many logical inconsistencies in every explanation I have heard — but I acknowledge that many sincere people have reported unexplained experiences that they have interpreted as ghosts.
