> On 13 Nov 2018, at 15:38, John Clark <johnkcl...@gmail.com> wrote: > > On Mon, Nov 12, 2018 at 9:35 PM Bruno Marchal <marc...@ulb.ac.be > <mailto:marc...@ulb.ac.be>> wrote: > > >> You've got it backwards, physics can simulate a Turing Machine but a > >> Turing Machine can't simulate anything or do anything at all without the > >> help of matter that obeys the laws of physics. > > > That is plainly false. If u is a universal machine/number, phi_u(x, y) > > emulate the number/machine x on the input y. > > So you say, but I see precisely ZERO evidence that "phi_u(x, y)" can emulate > a machine or emulate anything a or in fact do anything at all because > "phi_u(x, y)" never changes, not in time and not in space. You wrote > "phi_u(x, y)" in the above about 11 hours ago thousands of miles from me, > but here I am looking at "phi_u(x, y)" and "phi_u(x, y)" is still just > "phi_u(x, y)” .
Your confusion here is equivalent with confusing a far away galaxy with the telescope, or confusing a physical universe with a book on the physical universe. The emulation is in the meaning of “phi_u(x,y)”, not in the string of symbols referring to that meaning. > > >>A mathematical model is a description of something written in the language > >>of mathematics, like most descriptions it is not complete, > > > You are using “model” in the sense of the physicist, and logicians call > > that a theory, which can be seen indeed as a (incomplete) theory. But a > > model, in the logician sense is complete [...] > > Then logicians are talking about something that is self contradictory because > nothing mathematical or logical can be both complete and consistent. No mathematical and effective (sigma_1, checkable) theory can be complete. A model is complete by definition: it is what we intend to talk about. > > > [...] by definition. > > You have a tendency to use those 2 words as if they were the final mark of > authority, but the words "by definition" does not cause things to suddenly > spring into existence, that utterance is no more magical than "abracadabra". > Hogwarts Castle is a school for wizards BY DEFINITION, there is absolutely no > doubt about it, but do you think it would be worth your time to go looking > for it? But some existence can follow from definition, even, imprecise one. To prove that a computable function exist, just one example is enough, using a simple example. To prove that something is NOT computable, needs a precise mathematical definition. That is why we need Church, Turing, … Then, if you are OK that 2+2=4 and similar are true independently of you and me, computations and their many realisation all exists, in a provable way, in the arithmetical reality/model. > > > It is usually infinite, > > Yet another reason to suspect it does not exist. Indeed. Infinity exist only in the phenomenology. Just look ate the TOE I gave. None assumes infinity. I assume 0, s(0), s(s(0)), … only. > > > A model is a model of a theory. > > So I guess a model of a theory is a model of a model of a theory, and a model > of a model of a theory is a model of a model of a model of a theory, and a > model of…. You might decide one day to study a bit of mathematical logic. The notion of model applies to a theory, only, or to a machine, in a related sense. (In infinitary logic, where we allow alphabet with arbitrary cardinality, some models can be see as theory, but that has no uses in our context. Bruno > > John K Clark > > > > > -- > 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 > <mailto:everything-list+unsubscr...@googlegroups.com>. > To post to this group, send email to firstname.lastname@example.org > <mailto:email@example.com>. > Visit this group at https://groups.google.com/group/everything-list > <https://groups.google.com/group/everything-list>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- 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 firstname.lastname@example.org. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.