Eliezer_Yudkowsky comments on Demands for Particular Proof: Appendices - Less Wrong

26 Post author: Eliezer_Yudkowsky 15 February 2010 07:58AM

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Comment author: Nick_Tarleton 23 February 2010 04:13:19AM 0 points [-]

Why not 1/3^^^^^3?

Comment author: Eliezer_Yudkowsky 23 February 2010 04:27:53AM 3 points [-]

You can't imagine anything that improbable. Unless we adopt Robin's anthropic penalty, in which case "I am in a unique position to affect 3^^^^^3 other people" is that improbable.

Comment author: komponisto 23 February 2010 05:25:20AM *  9 points [-]

Why not 1/3^^^^^3?

You can't imagine anything that improbable.

Actually, the beauty of mathematics is that it enables us to imagine such things -- just as surely as it tells us that there ain't nothin' we're talkin' about that's anywhere near that.

Comment author: wedrifid 23 February 2010 11:59:59AM 8 points [-]

I can't imagine quarks either.

1/3^^^^^3 is a probability. A stupid probability, but a probability nonetheless. And if you declare 1/3^^^^^3 to be not a probability because of it's unimaginable uselessness then by the same standard I expect you to consider 3^^^^^3 'Not a Number'. I know you routinely use arbitrarily large numbers like 3^^^3 for decision theoretic purposes (on Halloween costumes!) and that is a number that is more or less chosen because it is already unimaginable.

Comment author: Liron 24 February 2010 01:39:08AM 1 point [-]

log_2(3^^^^^3) heads in a row?

Comment author: Eliezer_Yudkowsky 24 February 2010 03:28:51AM 4 points [-]

Coin's fixed.

Comment author: Liron 24 February 2010 04:54:25AM *  4 points [-]

Ah, so you meant: No physically possible series of Bayesian updates can promote a hypothesis to prominence if its prior probability is that low. And Peter meant: It is decision-theoretically useless to include a subroutine for tracking probability increments of 1/3^^^^^3 in your algorithm.

But the non-Bayesian source of your Bayesian prior might output 1/3^^^^^3 as the prior probability of an event -- as surely for the coin flip example as for Robin Hanson's anthropic one.

Comment author: Eliezer_Yudkowsky 24 February 2010 05:45:08AM *  3 points [-]

To be precise, it's impossible to describe any sense event with a prior probability that low. You can describe hypotheses conditional on which a macro-event has a probability that low. For example, conditional on the hypothesis that a coin is fixed to have a 1/3^^^3 probability of coming up heads, the probability of seeing heads is 1/3^^^3. But barring the specific and single case of Hanson's hypothesized anthropic penalty being rational, I know of no way to describe, in words, any hypothesis which could justly be assigned so low a prior probability as 1/3^^^3. Including the hypothesis that purple is falling upstairs, that my socks are white and not white, or that 2 + 2 = 5 is a consistent theorem of Peano arithmetic.

Comment author: wedrifid 24 February 2010 03:58:06AM 2 points [-]

How many dustspecks in the eye are you willing to bet on that?

Comment author: Nick_Tarleton 24 February 2010 03:37:54AM 2 points [-]

The log_2(3^^^^^3) consecutive binary digits of pi starting from number 3^^^^^3 are 0?

Comment author: Unknowns 24 February 2010 03:46:43AM 0 points [-]

Then our minds are "fixed" too, just like the coin.