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Prismattic comments on The self-fooling problem. - Less Wrong Discussion

10 Post author: PuyaSharif 10 October 2011 10:26PM

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Comment author: Prismattic 11 October 2011 12:49:08AM 19 points [-]

Go to the bank. Obtain several thousand coins of a denomination equal to the one you are looking for. Mix the important coin in with the rest of the money (WITHOUT first making any effort to remember exact imperfections from this particular coin). Scatter piles of coins in various likely and unlikely places around your house.

They gave you a needle. Make the house a haystack.

Comment author: Alejandro1 11 October 2011 03:14:28AM 6 points [-]

In the words of Chesterton's Father Brown:

"Where does a wise man hide a leaf? In the forest. But what does he do if there is no forest?"

"Well, well," cried Flambeau irritably, "what does he do?"

"He grows a forest to hide it in."

Comment author: betterthanwell 11 October 2011 06:10:49AM *  2 points [-]

Go to the bank. Obtain several thousand coins of a denomination equal to the one you are looking for.

This was the first approach I thought of. Make a haystack for the needle.

This will however allow you to find the haystack.

"Where is the coin? Right here, in the pile of coins."

Your coin finding self could beat your coin hiding self by scooping up all the coins,
bringing them before a judge and arbiter and saying "here it is."

You will likely have found the coin, even if you can not identify it.

If a judge can easily identify the coin, and you have found and presented the coin to the judge,
then it would be reasonable to say the coin is found.

Otherwise, the answer is lost to both the judge and the coin hider, much as if you ground it to a fine dust.

Save yourself the trouble and grind the coin into dust.

Destroy the answer. Make retrieval impossible.

(This was probably intended to be forbidden in the formulation of the problem, but it is not.)

Comment author: fortyeridania 12 October 2011 03:44:22PM 3 points [-]

Your coin finding self could beat your coin hiding self by scooping up all the coins, bringing them before a judge and arbiter and saying "here it is."

In that case, lock away the coin and hide the key among thousands of identical keys. Surely a wheelbarrow full of keys would not constitute a coin.

And if identifying the locked chamber (or container, or whatever) counts as finding the coin, then lock a bunch of them after hiding the coin in a randomly selected one.

Comment author: betterthanwell 11 October 2011 06:27:12AM *  3 points [-]

Trivial solutions for the problem: (Coin hider to wins over the coin finder.)

  • Loose the needle - not in a haystack - but in a large stack of needles.
  • Grind the coin in to dust. Destroy it's physical basis.

The first makes the coin lose it's uniqueness, the second makes the coin physically irretrievable.

No reason to play by implied rules, rules that only a human would think to follow anyway.

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