On 19 February 2014 00:15, Russell Standish <li...@hpcoders.com.au> wrote:
> On Tue, Feb 18, 2014 at 11:22:55PM +0000, David Nyman wrote: > > On 18 February 2014 22:34, Russell Standish <li...@hpcoders.com.au> > wrote: > > > > On Tue, Feb 18, 2014 at 02:06:37PM +0000, David Nyman wrote: > > > > > > > > I must admit it hasn't been entirely clear to me why you decided > that the > > > > MGA can go through without addressing the counterfactuals, especially > > > since > > > > Maudlin felt he had to address them in his alternative formulation. I > > > > appreciate that Maudlin proceeds by trivialising the amount of > activity > > > > involved in the computation whereas MGA relies on evacuating the > notion > > > of > > > > physical computation itself, but does the latter approach obviate the > > > need > > > > to account for any possible counterfactual activity? > > > > > > > > > > If the counterfactuals are physical (Multiverse situation), then we > > > are automatically in a robust universe (for which the reversal is > > > already addressed by step 7). > > > > > > Right. Sorry if I'm being a bit slow. I can see that if there is a > > Multiverse then we automatically get the physical counterfactuals in any > > given situation. But I'm not sure that I get the point that a physical > > Multiverse guarantees the actual physical computation of the UD (or > rather > > its completed trace), which I assume is necessary to the reversal (in the > > sense that the infinity of computation intrinsic to the UD* is assumed to > > swamp every competing measure). I guess that means that I haven't > > understood quite what is meant by robust here. Can you help with what I'm > > missing? > > Fair enough - it's a bit subtle. A quantum computation running in a > Multiverse has all possible states of its input bits executed > simulatenously. That is the meaning of a qubit. I can run a variant of > the dovetailer algorithm that actually executes its program in > parallel, exponentially speeding up the process. Our observed universe > has sufficient quantum computing resources to be able to run enough of > the UD to end up emulating conscious observers. > > It seems clear to me that the physical processes we see > instantiating consciousness are quantum in nature, spread out over the > Multiverse, executing a collection of programs like a dovetailer, > including conscious ones. > > So whilst the Multiverse may not be strictly speaking robust in the sense > of having infinite computational resources, it does have sufficient > resources to emulate enough of the dovetailer to include consious > programs, and in fact is doing so, by virtue of the fact we observe > consioud processes. This is enough for the distinction beween step 7 > and step 8. > Ah, right. So one has to keep in mind that it takes the running of the UD (or at least enough of it) to support a coherent formulation of CTM in the first place (essentially because once one assumes that consciousness supervenes on computation it becomes illegitimate to place arbitrary restrictions on what computations are deemed to exist). If so, assuming CTM, one can then use the a posteriori fact of conscious observation to justify the claim that the Multiverse must be robust enough (in that sense) to support the UD, especially given the independent plausibility of this assumption. Is that it, more or less? You're right that it's subtle. It's easy to miss (Edgar for one seems to miss it completely). It seems to require a conceptual leap to the necessity of a computational infinity with observer selection as the arbitrator of the stability of physical appearance (the Programmatic Library of Babel). Perhaps the UDA could spell this out more explicitly in step 7 (I can't bring to mind what it actually says at that point)? > > > > If the universe is not robust, then the > > > counterfactuals are not physical, and so if physical supervenience > > > were true, the counterfactuals are irrelevent to supervenience. > > > > > > > Yes, I get that part. So robust = Multiverse? > > > > Sort of. Maybe. :) Certainly, the presence of a UD entails a > Multiverse. And a Multiverse containing conscious entities is > sufficiently robust for the reversal to occur. > > BTW - for those wanting to know if I ever changed my mind - until a > year ago, I thought the Multiverse was a clear contraindicator to the > Maudlin/MGA argument. And recently the realisation that all programs > correspond to the proof of some sigma_1 proposition resolved a qualm I > had with the use of Theatetus's notion of knowledge when applied to > machines. > I'll have to think about that :) Cheers David > > > > ---------------------------------------------------------------------------- > Prof Russell Standish Phone 0425 253119 (mobile) > Principal, High Performance Coders > Visiting Professor of Mathematics hpco...@hpcoders.com.au > University of New South Wales http://www.hpcoders.com.au > > ---------------------------------------------------------------------------- > > -- > 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 everything-list+unsubscr...@googlegroups.com. > To post to this group, send email to everything-list@googlegroups.com. > 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. 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