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Juno_Watt 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: Juno_Watt 21 May 2013 05:27:32PM 0 points [-]

If you knew the initial conditions precisely enough, you would know whether the coin was in a white or black region of phase space, and you would then have a probability of either 1 or 0 for it coming up heads.

Not necessarily, because of quantum uncertainty and indeterminism -- and yes, they can affect macroscopic systems.

The deeper point is, whilst there is a subjective ignorance-based kind of probability, that does not by itself mean there is not an objective, in-the-territory kind of 0<p<1 probability. The latter would be down to how the universe works, and you can't tell how the universe works by making conceptual, philosophical-style arguments.

So the kind of probability that is in the mind is in the mind, and the other kind is a separate issue. (Of course, the existence of objective probability doesn't follow from the existence of subjective probability any more than its non existence does).