h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

(a thought experiment)

There is a big hairy monster in your bedroom. You cannot see it or hear it but it is there. If you do not switch off your bedroom light by eleven o'clock this evening, the monster will show itself and swallow you whole. If you do switch off the light, the monster will leave you alone.

There are two possible consequences of leaving the light on. Either nothing will happen, because the big hairy monster does not exist, or you will suddenly find yourself being eaten, because he does. Clearly, then - given that you have no desire to be consumed - it is safer to assume the monster does exist and to switch the bedroom light off before eleven o'clock.

The logic is impeccable but the conclusion is clearly absurd. Why should you do anything on this basis, when no evidence has been given to back up the claim ? What hairy monster ? What on earth is this person talking about ?

The fact is, this form of argument can be used to justify belief in more or less anything, no matter how absurd. All you need is a sufficiently horrible threat, and people will be scared into doing whatever you want; even committing murder.

To accept a supposition without tangible evidence is a sign of credulity. The only basis we have for judging the merit of opposing ideas is analysis of the physical world. If the weight of evidence supports one idea, then we accept that this idea is most likely to be true. If there is little evidence to support the idea, or there is substantial evidence against it, we say that it is untrue. This is not a perfect system, and new evidence constantly forces us to rethink our conclusions, but it is the best system we have and it is the only fair means of evaluating ideas.

I believe this. You believe that. If neither of us offers any proof, all we can do is bang our heads together until one of us has a brain haemorrhage.

The big hairy monster may or may not exist.

The burden of proof lies with those who believe that he does.
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Very good article, by the way

MDS

it gets worse than that - what happens if after your mother telling you about this hairy monster, your father (in an attempt to stir up trouble, perhaps) tells you that if you *do* switch off your bedroom light by 11, then a hairless monster will show itself and swallow you whole!

Thanks for the compliment But it'd be even nicer in the appropriate peer review thread...