On 14/08/2017 12:44 pm, Stathis Papaioannou wrote:
On Mon, 14 Aug 2017 at 11:30 am, Bruce Kellett <[email protected] <mailto:[email protected]>> wrote:On 14/08/2017 11:19 am, Stathis Papaioannou wrote:On Mon, 14 Aug 2017 at 10:30 am, Bruce Kellett <[email protected] <mailto:[email protected]>> wrote: On 14/08/2017 2:51 am, Stathis Papaioannou wrote:On Sun, 13 Aug 2017 at 9:38 pm, Bruce Kellett <[email protected] <mailto:[email protected]>> wrote: I think the problem I see is in the insistence that one restrict the subjects of the duplication to first person knowledge. Their knowledge of the protocol cannot be purely 1p -- there has to be a 3p component in that they are told the set up, and they have sufficient background 3p knowledge to trust the operator, etc. Then, after duplication, they also have access to 3p knowledge about both duplicates -- they can arrange to communicate, for example. So they can easily become aware of the fact that the person that remembers being Helsinki man sees both Moscow and Washington. My point here is that if you restrict them to 1p knowledge after the duplication, you must, in order to be consistent, restrict them to just 1p knowledge before the experiment; in which case they are necessarily unaware of the details of the protocol and will have a different perception of what has happened. In the case of restriction to 1p knowledge the situation becomes much more analogous to what happens in QM where experiments might have multiple outcomes. In that case there is no possibility of communication between the different branches of the wave function, so there is genuine uncertainty about outcomes, and probabilities are estimated from limiting relative frequencies in the usual way. If one derives and/or applies the Born Rule in QM, then one can assign low probabilities to untypical sequences of results and the like. If you mix 1p and 3p knowledge in the duplication scenario, you lose this parallel with QM because the analogous 3p knowledge is not available in QM. If someone believes the MWI is true, then he is aware of the protocol and trusts the operator. In duplication experiments there is no logical reason why the copies could not be kept ignorant of each otherAnd there is no logical reason that prevents them from arranging beforehand to communicate after the experiment -- in Helsinki, I could decide to post my subsequent location to Facebook, and communicate with other similar posts. But if they were prevented from communicating would it make any fundamental difference to the experiment? and there is no logical reason why copies in the MWI can't see what each other is doing. Such inter-branch communication in MWI is physically impossible. This is the main reason why person duplication experiments can never emulate QM, MWI or not. It is physically impossible, but what fundamental difference would it make if you could communicate with a copy in a parallel world who diverged from you a while ago? Would you suddenly feel that you weren't you, or that you were in two places at once?The ability to communicate, or the physical impossibility of such communication, is the fundamental difference between the duplication scenario and quantum MWI. It changes the probabilities: just think of duplication of the apparatus in a spin measurement experiment without simultaneous duplication of the experimenter -- then it is clear that I get both spin up and spin down, in my laboratory, in front of my eyes. This is not possible in MWI since the branches are, by definition, non-interacting.The equivalent examples would be if the experimenter along with the lab and the apparatus were duplicated, with one experimenter seeing spin up and the other spin down. What difference would it then make if the experimenters, now two of them, walked down the road to see each other, or if they were prevented from doing so?
I am not sure that this is equivalent. It could just be that there were two experiments done. I don't think that my example of the spin measurement really works as a parallel either.
The point, as I see it, is that if, after duplication, the copies can communicate, and they agree that they both have psychological continuity with the original person, and that, consequently, the original person saw both cities/results. If they cannot communicate, as in QM, then they are debarred from such direct knowledge -- the doppelganger is only a theoretical possibility. So the ability to communicate with the other branch is a fundamental difference between the duplication scenario and QM; different information leads to different estimates of probabilities.
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