The idea of ghosts, like a lot of paranormal phenomena, falls flat on it's basic inability to remain consistent in it's description. We're meant to believe that ghosts are the still-present souls or essences of dead human beings. But if this were the case then wouldn't we be seeing a gradual increase in ghost sightings as time went on? It seems every ghost encountered is from some "18th Century milk farm" as oppose to the more recently decease. Indeed despite advances in medical techniques the amount of people dying each day is much higher than it was in the past by sheer virtue of the exponentially larger amount of people present. If it were the case that anyone who dies is eligible for ghostdom we would be bumping into ghosts left, right and centre by now. Also, has anyone ever noticed that ghosts only seem to come out at night or when it's dark? Are ghosts kind of like bats in that they're nocturnal? If ghosts are really humans then surely they would be more inclined to go about their business during the day? This also goes against notions of the afterlife and reincarnation that all these religious types seem so enamoured with. The very concept of souls remaining on earth suggests that the system is either flawed or doesn't exist so which is it?