2014-02-25 1:05 GMT+01:00 chris peck <[email protected]>: > Hi Quentin > > > > *>>As I see from the abstract, he doesn't reject probability calculus, > only the interpretation of it... I'll read the article later. * > > Greaves rejects subjective uncertainty. With respect to spin up and spin > down pay special attention to the point in section 4.1 where, in discussion > of a thought experiment formally identical to Bruno's step 3, he argues: > > *"What ... should Alice expect to see? Here I invoke the following > premise: whatever she knows she will see, she should expect (with > certainty!) to see. So, she should (with certainty) expect to see spin-up, > and she should (with certainty) expect to see spin-down."* > > That's nonsense, and contrary to observed fact.
> > *>> One reason for MWI, is to explain the observed QM probabilities... * > > No, MWI was devised in response to the measurement problem but in > abandoning wave function collapse Everett ends up with a theory which is > very parsimonious but entirely deterministic. How to then account for > probability in a determinist framework has become the Achilles heel of MWI > not its raison d'être. > > Since Everett there have been numerous attempts to smuggle an account of > probability back into the theory, and more recent attempts: Deutsch, > Wallace, Greaves etc., do that by abandoning the concept of subjective > uncertainty altogether and replacing it with some kind of rational action > principle. In otherwords, you can expect to see spin up and spin down, but > you should act as if there was some objective bias towards one or the > other. The approach comes complete with its own set of philosophical > problems. > > The point is that how probability fits into MWI's determinist framework, > or any TofE really, is still an open question. And to argue that must > reject MWI if they reject Brunos probability sums is plain wrong. Im happy > to find myself in the company of Oxford Dons like Deutsch and Greaves. > David Deutsch does not reject probability... or could you please show a quote where he does. > > > *>> your theory is disproven by fact... you never see constant spin up... > which should be the case if the probability to measure spin up was one.* > > See above. > Well what I see does not seem to make sense. Regards, Quentin > > All the best > > Chris. > > ------------------------------ > From: [email protected] > Date: Mon, 24 Feb 2014 16:32:01 +0000 > > Subject: Re: 3-1 views (was: Re: Better Than the Chinese Room) > To: [email protected] > > > On 24 February 2014 15:50, Bruno Marchal <[email protected]> wrote: > > > On 24 Feb 2014, at 02:41, David Nyman wrote: > > On 24 February 2014 01:04, chris peck <[email protected]> wrote: > > *>>This is the same as saying that I will experience all possible futures > in the MWI - but by the time I experience them, of course, the version of > me in each branch will be different, and it always seems to me, > retrospectively, as though I only experienced one outcome.* > > Each duplicate will only experience one outcome. I don't think there is > any disagreement about that. The problems occur when considering what the > person duplicated will experience and then what probability he should > assign to each outcome and that seems to me to depend on what identity > criterion gets imposed. Its a consideration I've gone into at length and > won't bore you with again. But I will say that where you think that what > Bruno wants is just recognition that each duplicate sees one outcome, I > think that he actually wants to show that 3p and 1p probability assignments > would be asymmetric from the stand point of the person duplicated. > Certainly for me he doesn't manage that. > > > Correct me if I'm misremembering Chris, but I seem to recall proposing to > you on a previous occasion that Hoyle's pigeon hole analogy can be a useful > way of tuning intuitions about puzzles of this sort, although I appear to > be the sole fan of the idea around here. Hoyle's idea is essentially a > heuristic for collapsing the notions of identity, history and continuation > onto the perspective of a single, universal observer. From this > perspective, the situation of being faced with duplication is just a random > selection from the class of all possible observer moments. > > Well, the "just" might be not that easy to define. > > If the universal observer is the universal machine, the probability to get > a computational history involving windows or MacOS might be more probable > than being me or you. > > > But how would "you" remember that? > > > > I am not sure that the notion of "observer moment" makes sense, without a > notion of scenario involving a net of computational relative states. > > I think the hypostases describe a universal person, composed from a > universal (self) scientist ([]p), a universal knower ([]p & p), an observer > ([]p & <>p), and a feeler ([]p & <>p & p)). > > But I would not say that this universal person (which exist in arithmetic > and is associated with all relatively self-referential correct löbian > number) will select among all "observer moment". > > > Well, perhaps "eventually" it will select all of them, if we can give some > relevant sense to eventually in this context. And I suppose Hoyle's point > is that if one imagines a logical serialisation of all such moments, its > order must be inconsequential because of the intrinsic self-ordering of the > moments themselves. Essentially he is saying that the panoptic bird view is > somehow preserved at the frog level, at the price of breaking the > simultaneity of the momentary views. > > > The "hypostatic" universal person is more like a universal baby, which can > split in a much larger spectrum of future 1p histories, but from its first > person perspective it is like it has still to go through the histories to > get the right relative statistics on his most probable universal neighbors. > > > Won't this still be effectively satisfied by Hoyle's heuristic? ISTM that > "going through the histories" is a notion that splits in the 3p and 1p > views. I suppose this is equivalent to conceiving observer moments as > self-ordering monads in terms of which any random serialisation over the > entire class must eventually preserve the right relative statistics. > "Eventually" here relies on a similar opacity to delays in continuation as > you argue in the UDA, plus the reliance on prior relativisation to some > specific spatial-temporal orientation, to get a 1p notion of temporal > order. But perhaps this formulation of a discrete observer moment is > incompatible with comp? > > Of course, in the arithmetical reality, it don't get it, it is an > indexical internal point of view. > > > Perhaps it gets it "eventually", in the sense I outline above? > > > > The situations of having been duplicated one or more times are then just > non-simultaneous selections from the same class. This gives us a consistent > way of considering the 3p and 1p (or bird and frog) probabilities > symmetrically. That is, it is now certain that I will confront each and > every 3p continuation from a unique 1p perspective, just not simultaneously. > > That said, this approach retains a quasi-frequency interpretation of > probability in the case that there are fungible or equivalent > continuations. For example, if the protocol mandates that I will be > duplicated 100 times and 99 of my copies will be sent to a red room and one > to a blue room, it would be rational to anticipate a higher "probability" > of continuation associated with the larger class, even though each > continuation is individually certain in a different underlying sense. This > is just to say that subjective uncertainty (or the expectation of > probabilistic outcomes) is a function of incomplete knowledge at any given > point in the sequence. > > > OK. > > > I know that Bruno quarrels with Hoyle's idea as being superfluous to, or > possibly even incompatible with, comp > > > I think about it. I try to make sense of it. That might have sense, but > then it remains to look at it in arithmetic. > I mean the relations between a person and the universal person "in her" > is complex, and the splitting between []p and []p & p is part of it. > > but personally I still find it a neat heuristic for pumping one's > intuition on the indeterminacy of first-personal expectations. > > > OK. > It is just that I expect platonism to be counter-intuitive and so > intuition pump must be handled with care. But you know that. I just try to > understand the point. > > > Absolutely. I appreciate your interest. > > David > > > > http://iridia.ulb.ac.be/~marchal/ > > > > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/groups/opt_out. > > > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/groups/opt_out. > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/groups/opt_out. > -- All those moments will be lost in time, like tears in rain. 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