Eliezer_Yudkowsky comments on Where Recursive Justification Hits Bottom - Less Wrong

41 Post author: Eliezer_Yudkowsky 08 July 2008 10:16AM

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Comment author: Eliezer_Yudkowsky 09 July 2008 05:08:22AM 1 point [-]

An anti-Laplacian prior is defined in the obvious way; if you've observed R red balls and W white balls, assign probability (W + 1) / (R + W + 2) of seeing a red ball on the next round.

An anti-Occamian prior is more difficult, for essentially the reasons Unknown states; but let's not forget that, in real life, Occam priors are technically uncomputable because you can't consider all possible simple computations. So if you only consider a finite number of possibilities, you can have an improper prior that assigns greater probability to more complex explanations, and then normalize with whatever explanations you're actually considering.

Comment author: Will_Sawin 28 March 2011 11:43:28PM 1 point [-]

WRW has probability 1/2 * 2/3 * 1/2 = 1/6

WWR has probability 1/2 * 1/3 * 3/4 = 1/8

This is coherent if you require that the probability of different permutations of the same sequence be the same. An Anti-Laplacian urn must necessarily be finite.

On the other hand, Laplace assigns both a probability of 1/12.