On Wed, May 13, 2015 at 02:07:52PM +0200, Bruno Marchal wrote: > > On 13 May 2015, at 08:20, Russell Standish wrote: > > >On Wed, May 13, 2015 at 03:45:09PM +1000, Bruce Kellett wrote: > >> > >>That might be the idea. It is difficult to get to this, though, > >>since the notion of "primary materialism" doesn't really feature in > >>the argument. Before we get to the MGA, the dovetailer has been > >>introduced, and this is supposed to emulate the generalized brain > >>(even if the generalized brain is the whole galaxy or even the > >>entire universe) infinitely often, and the laws of physics emerge > >>from the statistics of all UD-computations passing through my actual > >>state. > >> > > > >I can get it, but by an indirect route. > > > >Basically, the MGA shows a contradiction between computationalism and > >physical supervenience. But only for non-robust ontologies. > > But it is the only place where we need it. In robust ontologies, > UDA1-7 is enough (to get the problem, not his solution!). > > > > >For a > >robust ontology, counterfactuals are physically instantiated, > >therefore the MGA is invalid. > > I don't see this. The "if A then B else C" can be realized in a > newtonian universe, indeed in the game of life or c++. > And the duplication of universe, one where A is realized, and B is > realized > + one in which A is not realized and C is realized, > might NOT makes a non counterfactually correct version of that > if-then-else suddenly counterfactually correct.
It makes the non counterfactually correct version _physically_ different from the counterfactually correct version. So one cannot drive the MGA conclusion, which relies on the versions being physically indistinguishable. > > Counterfactuals and MWI (and robustnesse) are a priori independent > notions. > Sure - but the MGA (if valid) connects them. > > > > >Now physical supervenience has been demonstrated to a high level of > >empirical satisfaction. > > I don't think so, unless you mean physical in some non aristotelian > sense, in which case you are right, but that does not falsified > comp, in that case. I mean in the usual sense of physical - atom, electrons and so on. > > > > >So we can conclude either that > >computationalism is falsified, or that our ontology is robust. But if > >the ontology is robust, UDA 1-7 demonstrates the reversal - physics > >depends only on the properties of the universal machine, not on any > >other ontological property of "primitive reality". Therefore we can > >excise the "physicalness" of ontology - anything capable of universal > >computation will do, such as arithmetic. > > > >But this chain of argument is not the usual one, so clearly it needs > >to be examined critically. Bruno has not given his imprimatur to it, > >dor example. Also, the MGA itself needs to shoring up, particularly > >with respect to the requirement of counterfactual correctness, and > >also that other issue I just raised about the recording player > >machinery changing the physical arrangement, perhaps by just enough to > >render physical supervenience toothless too. In which case the whole > >thing falls apart. > > This is a bit unclear to me. You might decompose your thought in > some steps, with what is assumed and what is derived, as I am lost > here. > Did you mean the first paragraph of the second? The first paragraph is my argument, that I asking you to focus on in the first sentence of the second para. The latter portion of the second paragraph is just referring to all the niggling issues we've been discussing in this thread - the role of intuition and absurdity, whether counterfactual correctness is required for consciousness and the issue of whether a replayed recording really is physically identical in a non-robust setting (I suspect that it can be made to be, but the usual formulations such as the MGA or Maudlin's are not so clear cut, as the machinery required to implement the replaying is usually ignored). -- ---------------------------------------------------------------------------- Prof Russell Standish Phone 0425 253119 (mobile) Principal, High Performance Coders Visiting Professor of Mathematics [email protected] 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 [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/d/optout.
