Paigntonian, as far as I'm concerned, people, whether religious or not, will believe whatever they believe. Fair enough.
It's only when someone tries to add a rational reason, that it can be argued against.
But, it goes without saying, that as the definition of a "ghost" is the return of a dead person, it is only going to be someone who believes in an afterlife. And if you can believe that- with no evidence and nobody returning to tell us- you can probably believe in ghosts.
It's more how you choose to interpret it yourself, than any psychology knowledge or physics etc.