The Mystery of the Haunted Rationalist

Fol­lowup to: Si­mul­ta­neously Right and Wrong

“The most mer­ciful thing in the world, I think, is the in­abil­ity of the hu­man mind to cor­re­late all its con­tents.”

- H.P. Love­craft, The Call of Cthulhu

There is an old yarn about two skep­tics who stayed overnight in a sup­pos­edly haunted man­sion, just to prove they weren’t su­per­sti­tious. At first, they laughed and joked with each other in the well-lit mas­ter bed­room. But around eleven, there was a thun­der­storm—hardly a rare event in those parts—and all the lights went off. As it got later and later, the skep­tics grew more and more ner­vous, un­til fi­nally around mid­night, the stairs lead­ing up to their room started to creak. The two of them shot out of there and didn’t stop run­ning un­til they were in their car and driv­ing away.

So the skep­tics’ emo­tions over­whelmed their ra­tio­nal­ity. That hap­pens all the time. Is there any rea­son to think this story proves any­thing more in­ter­est­ing than that some skep­tics are cow­ards?

The Kore­ans have a su­per­sti­tion called “fan death”: if you sleep in a closed room with a fan on all night, you will die. Some­thing about the fan blades shred­ding the oxy­gen molecules or some­thing. It all sounds pretty far-fetched, but in Korea it’s en­dorsed by ev­ery­one from doc­tors to the gov­ern­ment’s offi­cial con­sumer safety board.

I don’t be­lieve in ghosts, and I don’t be­lieve in fan death. But my re­ac­tions to spend­ing the night in a haunted man­sion and spend­ing the night with a fan are com­pletely differ­ent. Put me in a haunted man­sion, and I’ll prob­a­bly run out scream­ing the first time some­thing goes bump in the night1. Put me in a closed room with a fan and I’ll shrug and sleep like a baby. Not be­cause my su­pe­rior ra­tio­nal­ity has con­quered my fear. Be­cause fans just plain don’t kill peo­ple by chop­ping up oxy­gen, and to think oth­er­wise is just stupid.

So al­though it’s cor­rect to say that the skep­tics’ emo­tions over­whelmed their ra­tio­nal­ity, they wouldn’t have those emo­tions un­less they thought on some level that ghosts were worth get­ting scared about.

A psy­chol­o­gist armed with the the­ory of be­lief-pro­fes­sion ver­sus an­ti­ci­pa­tion-con­trol would con­clude that I pro­fess dis­be­lief in ghosts to fit in with my ra­tio­nal­ist friends, but that I an­ti­ci­pate be­ing kil­led by a ghost if I re­main in the haunted man­sion. He’d dis­miss my skep­ti­cism about ghosts as ex­actly the same sort of be­lief in be­lief af­flict­ing the man who thinks his dragon is per­me­able to flour.

If this psy­chol­o­gist were re­ally in­ter­ested in in­ves­ti­gat­ing my be­liefs, he might offer me X dol­lars to stay in the haunted man­sion. This is all a thought ex­per­i­ment, so I can’t say for cer­tain what I would do. But when I imag­ine the sce­nario, I vi­su­al­ize my­self still run­ning away when X = 10, but fight­ing my fear and stay­ing around when X = 1000000.

This looks sus­pi­ciously like I’m mak­ing an ex­pected util­ity calcu­la­tion. Prob­a­bil­ity of be­ing kil­led by ghost * value of my life, com­pared to a mil­lion dol­lars. It also looks like I’m us­ing a rather high num­ber for (prob­a­bil­ity of be­ing kil­led by ghost): cer­tainly still less than .5, but much greater than the <.001 I would con­sciously as­sign it. Is my mind haunted by an in­visi­ble prob­a­bil­ity of ghosts, ready to jump out and ter­rify me into mak­ing ir­ra­tional de­ci­sions?

How can I defend my­self against the psy­chol­o­gist’s ac­cu­sa­tion that I merely pro­fess a dis­be­lief in ghosts? Well, while I am run­ning in ter­ror out of the man­sion, a bookie runs up beside me. He offers me a bet: he will go back in and check to see if there is a ghost. If there isn’t, he owes me $100. If there is, I owe him $10,000 (payable to his next of kin). Do I take the bet?

Thought ex­per­i­ments don’t always work, but I imag­ine my­self tak­ing the bet. I as­sign a less than 1100 chance to the ex­is­tence of ghosts, so it’s prob­a­bly a good deal. The fact that I am run­ning away from a ghost as I do the calcu­la­tion changes the odds not at all.

But if that’s true, we’re now up to three differ­ent lev­els of be­lief. The one I pro­fess to my friends, the one that con­trols my an­ti­ci­pa­tion, and the one that in­fluences my emo­tions.

There are no ghosts, pro­fess skep­ti­cism.
There are no ghosts, take the bet.
There are ghosts, run for your life!


1: I worry when writ­ing this that I may be alone among Less Wrong com­mu­nity mem­bers, and that the rest of the com­mu­nity would re­main in the man­sion with min­i­mal dis­com­fort. If “run scream­ing out of the man­sion” is too dra­matic for you, will you agree that you might, af­ter the floor­boards get es­pe­cially creaky, feel a tiny urge to light a can­dle or turn on a flash­light? Even that is enough to pre­serve the point I am try­ing to make here.