Agreed- much like fairy sightings, ghost sightings appear break down into several quite distinct 'types' of sightings, so 'vague shapes', solid representations of people, translucent figures). You'd probably be able to extract some interesting patterns to sightings by tabulating them, adding columns for features of the 'sighting' and also adding in stuff like weather, location, time of day, some info about the witness etc. etc.I'm afraid I've always doubted the existence of a "Unified Theory" of what a ghost is, considering the wide-range of phenomena claimed.
Or astral travel. On another thread, I relayed the experience I had at 7 or 8 when I saw my youngest brother standing, clear as day in his pjs, at the side of my bed looking down at me early one morning. He might have been 1 1/2 to 2 years old because he was walking. This was not an uncommon thing for him to do as he'd join me and my sister in bed. I whispered his name, and he slowly disappeared. Was he astral projecting? I was not dreaming because I had woken and then dived right under my covers when he disappeared.As did Gary Numan. The person you saw may not have been dead but rather time-slipped from their time to yours then back again
An interesting OP!
If what we call 'ghosts' are related to traumatic events, then we'd see lots of battlefield and murder ghosts.
If related to numbers of deaths, then we'd be seeing large numbers of Mediaeval Black Death victims, pople who perished in other pandemics such as 1918 Spanish 'Flu, WWII ghosts (conservatively estimated total at c. 50,000,000 total deaths) and previous/latter genocides...
I guess there could be two reasons and sightings do fit into two categories, there are those that are like timeslip cases where the image is just going about life and those were the image appears to be sentient to it's surroundingsAs someone who is pretty open minded when it comes to the subject of the phenomena we call ghosts, this area is always a major stumbling block for me. If we suspend any disbelief for a moment, and accept it all as real, then trauma cannot be a major establishing factor - because, if it were, the world would be utterly overtaken by the ghosts of the dead. And really, the same goes for all the other reasons.
Like you @AnonyJ my own experiences have been of an aural nature. I am more or less convinced that at least two of these actually happened, and are not a product of my imagination - but, despite that sureness, the 'why' is completely beyond me, and I've never heard a convincing reason.