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Perplexed comments on Probability is in the Mind - Less Wrong

60 Post author: Eliezer_Yudkowsky 12 March 2008 04:08AM

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Comment author: Perplexed 03 July 2011 08:44:28PM 1 point [-]

As I understand it, EY's commitment to MWI is a bit more principled than a choice between soccer teams. MWI is the only interpretation that makes sense given Eliezer's prior metaphysical commitments. Yes rational people can choose a different interpretation of QM, but they probably need to make other metaphysical choices to match in order to maintain consistency.

Comment author: Peterdjones 03 July 2011 09:16:16PM *  0 points [-]

He still shouldn't be stating it as a fact when it based on "commitments".

Comment author: [deleted] 03 July 2011 09:33:34PM *  -2 points [-]

Yes rational people can choose a different interpretation of QM, but they probably need to make other metaphysical choices to match in order to maintain consistency.

Aumann's agreement theorem.

Comment author: Eugine_Nier 04 July 2011 07:33:38AM 3 points [-]

Aumann's agreement theorem.

assumes common priors, i.e., a common metaphysical commitment.

Comment author: [deleted] 04 July 2011 07:42:21AM 2 points [-]

However, Robin Hanson has presented an argument that Bayesians who agree about the processes that gave rise to their priors (e.g., genetic and environmental influences) should, if they adhere to a certain pre-rationality condition, have common priors.

The metaphysical commitment necessary is weaker than it looks.

Comment author: MarkusRamikin 07 July 2011 10:47:35AM *  1 point [-]

This theorem (valuable though it may be) strikes me as one of the easiest abused things ever. I think Ayn Rand would have liked it: if you don't agree with me, you're not as committed to Reason as I am.

Comment author: [deleted] 07 July 2011 04:42:14PM 0 points [-]

If you don't agree with me, you're not as committed to Reason as I am.

Except that isn't what I said.

If MWI is wrong, I want to believe that MWI is wrong. If MWI is right, I want to believe MWI is right.

Comment author: jsalvatier 07 July 2011 04:58:23PM 1 point [-]

I believe he's saying that rational people should agree on metaphysics (or probability distributions over different systems). In other words, to disagree about MWI, you need to dispute EY's chain of reasoning metaphysics->evidence->MWI, which Perplexed says is difficult or dispute EY's metaphysical commitments, which Perplexed implies is relatively easier.

Comment author: Islander 25 July 2011 07:28:13PM 0 points [-]

That's interesting. The only problem now is to find a rational person to try it out on.

Comment author: [deleted] 14 July 2013 08:37:33PM *  1 point [-]

MWI distinguishes itself from Copenhagen by making testable predictions. We simply don't have the technology yet to test them to a sufficient level of precisions as to distinguish which meta-theory models reality.

See: http://www.hedweb.com/manworld.htm#unique

In the mean time, there are strong metaphysical reasons (Occam's razor) to trust MWI over Copenhagen.

Comment author: OccamsTaser 14 July 2013 09:14:21PM 3 points [-]

In the mean time, there are strong metaphysical reasons (Occam's razor) to trust MWI over Copenhagen.

Indeed there are, but this is not the same as strong metaphysical reasons to trust MWI over all alternative explanations. In particular, EY argued quite forcefully (and rightly so) that collapse postulates are absurd as they would be the only "nonlinear, non CPT-symmetric, acausal, FTL, discontinuous..." part of all physics. He then argued that since all single-world QM interpretations are absurd (a non-sequitur on his part, as not all single-world QM interpretations involve a collapse), many-worlds wins as the only multi-world interpretation (which is also slightly inaccurate, not that many-minds is taken that seriously around here). Ultimately, I feel that LW assigns too high a prior to MW (and too low a prior to bohmian mechanics).

Comment author: [deleted] 15 July 2013 03:23:31AM *  0 points [-]

It's not just about collapse - every single-world QM interpretation either involves extra postulates, non-locality or other surprising alterations of physical law, or yields falsified predictions. The FAQ I linked to addresses these points in great detail.

MWI is simple in the Occam's razor sense - it is what falls out of the equations of QM if you take them to represent reality at face value. Single-world meta-theories require adding additional restrictions which are at this time completely unjustified from the data.