It’s very rare that a precommitment to holding a belief in spite of the evidence is the best way to investigate a topic related to that belief.
What valid very rare cases of this do you think of? One that comes to my mind is that at least might be valid is that of “faking it ‘till you make it”. People precommit to holding a belief for a while in spite of the evidence in order to improve qualities that depend on them holding that belief. Unfortunately, I wasn’t able to find conclusive studies on whether “faking it ‘till you make it” works for psychological improvement in general with a quick search. The closest that I have found is a study linked to from the Wikipedia page on the placebo effect that shows a specific case in which placebo is shown to work without deception on the doctors’ part (i.e., they tell patients it’s a placebo).
In my hypothetical I imagine belief in ghosts to be a belief that is very harmful conditional on it being true and you holding it. Can you suggest a better way to investigate it or do you think that it isn’t a valid very rare case even though no such way exists?
(Also, in case this played some role in why my original comment got downvoted, I would like to clarify to I do not consciously hold the belief that “ghosts will try to scare you to death” or other beliefs contingent on the existence of ghosts in reality. My real belief is probably closer to “Entities that are only able to interact with people’s minds make for interesting fictional scenarios.”)
Edit: fixed links. Edit 2: spelling and extra ).
If I believed in ghosts and wanted to investigate a haunted mansion I think it would be in my best interest to persuade myself temporarily to not believe in ghosts for the length of the investigation. In fact, I’d benefit only if I turned myself into a Narnia-style sceptic about them (one who wouldn’t believe or alieve in them in spite of the evidence). Given what I think are the rules of how ghosts are supposed to work [1] I would assume that a ghost out to kill me couldn’t do so by physical violence (e.g., lifting and throwing a kitchen knife—unless it was a poltergeist) but would instead try to scare me to death (e.g., by causing a heart attack, a human factor accident or suicide). Armed with that knowledge I’d want persuade myself to reject the belief in ghosts on a gut level so as to lower my fear and prevent death. However, by doing so I would also lose my incentive to investigate haunted mansions in the first place, so I_{pre-ghost sceptic} would have to find a way to precommit to the investigation and to revert back to having a belief in ghosts afterwards. A monetary bet could work for the former.
[1] As absorbed by me from popular culture. Admittedly, if I did believe in ghosts would probably have followed ghost lore and would now have a somewhat different set of assumptions about “ghost rules”.