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cousin_it comments on What's wrong with this picture? - Less Wrong Discussion

15 Post author: CronoDAS 28 January 2016 01:30PM

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Comment author: cousin_it 28 January 2016 04:51:26PM *  9 points [-]

I don't see the paradox. P(Alice saw this sequence) is low, and P(Alice presented this sequence) is low, but P(Alice saw this sequence | Alice presented this sequence) is high, so Bob has no reason to be incredulous.

Comment author: Brillyant 28 January 2016 05:05:53PM 5 points [-]

Bob has always been like this.

Comment author: OrphanWilde 28 January 2016 06:46:45PM 1 point [-]

I think, but am not certain, that you're missing the point, by examining Bob's incredulity rather than the problem as stated. Let's say your probability that the universe is being simulated is 2^x.

Alice flips a coin (x+1) times. You watch her flip the coins, and she carefully marks down the result of each flip.

No matter what sequence you watch, and she records - that sequence has less likelihood of having occurred naturally than that the universe is simulated, according to your priors. If it helps, imagine that a coin you know to be fair turns up Heads each time. (A sequence of all heads seems particularly unlikely - but every other sequence is equally unlikely.)

Comment author: cousin_it 29 January 2016 01:24:55AM *  3 points [-]

I agree that the probability of seeing that exact sequence is low. Not sure why that's a problem, though. For any particular random-looking sequence, Bob's prior P(see this sequence | universe is simulated) is pretty much equal to P(see this sequence | universe is not simulated), so it shouldn't make Bob update.