AlanCrowe comments on Bell's Theorem: No EPR "Reality" - Less Wrong

16 Post author: Eliezer_Yudkowsky 04 May 2008 04:44AM

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Comment author: VAuroch 18 November 2013 10:44:44AM 4 points [-]

It is a personal peeve when any explanation of the Bell Inequality fails to mention the determinist Big Loophole: It rules out nearly all local hidden-variable theories, except those for which the entire universe is ruled by hidden variables. If you reject the assumption of counterfactual definiteness (the idea that there is a meaningful answer to the question "what answer would I have gotten, had I conducted a different experiment?"), local hidden variable theories are not ruled out. This leads to superdeterminism and theories which assume that, through either hidden variables stretching back to t=0 or backwards-in-time signals, the universe accounted for the measurement and the result was determined to match.

This is, in fact, what I held to be the most likely total explanation for years, until I better understood both its implications and MWI. Which, in fact, also rejects counterfactual definiteness. MWI does it one better; it rejects factual definiteness, the idea that there is a well-defined answer to the question "What answer did I get?", since in alternate worlds you got different answers.

Comment author: AlanCrowe 18 November 2013 11:59:03AM 3 points [-]

That helps me. In his book Quantum Reality, Nick Herbert phrases it this way:

The Everett multiverse violates the CFD assumption because although such a world has plenty of contrafactuality, it is short on definiteness.

which is cutely aphoristic, but confused me. What does contrafactuality even mean in MWI?

Pointing out that MWI rejects factual definiteness clears things up nicely.