On Thu, Oct 1, 2015 at 12:01 PM, Bruno Marchal <[email protected]> wrote:
>> >> When I say "physical computation" and you demand a definition of that and >> when I respond with "a computation done with physics" and you demand a >> definition of that too then I believe it is perfectly acceptable for me to >> either get off the silly definition merry-go-round or to demand a >> definition of my own, a definition of definition. > > > > But this distracts us from what we should focus on. I agree it's a silly waste of time, so why did you demand a definition of physical computation ? > > A computation can be defined by what universal machines do. But that universal machine can't do a damn thing without the help of physics, therefore your definition is unimportant. > > A universal machine is defined by a number u such that phi_u(x, y) = > phi_x(y). You can define it however you like, but if that machine isn't made of matter that obeys the laws of physics it's not going to be doing any calculations, and it's not going to be doing anything else either. > > None of those theories assume anything material. And none of those theories can perform calculations, no theory can, only physical material can do that. >> >>> you use the term computation in the sense of Church-Turing. >> >> >> >> I use the term "computation" in the sense of actually finding a >> particular solution to a particular problem in arithmetic; and neither >> Church nor Turing were fools so they meant the same thing. > > > > Come on! You are the guy which pretend to accept computationalisme. Why on earth would I pretend to accept computationalism if I did not? > >> A Turing Machine is physical, > > > Absolutely not. Turing made it looking like that because he wanted to > capture the essence of what a human does when he compute a function with > pencil and paper. Turing wanted to capture the essence of what ANYTHING does when a calculation is actually made; not talked about, not theorized, not defined, but actually MADE. > > > > he gave a purely mathematical definition That's nice, but defining a calculation and making a calculation is not the same thing, just as "a fast red car" is NOT a fast red car. Definition s can't make calculations, only matter that obeys the laws of physics can do that. >> there is ZERO evidence that arithmetic can calculate anything without >> the help of physics > > > Zero evidences enough when we prove a theorem! But that is not nearly enough if you want to know a particular solution to a particular problem in arithmetic because neither proofs nor theorems can make a calculation; for that you need physics. > >> as of September 30 2015 every calculation ever observed has involved >> matter that obeys the laws of physics. No exceptions, not a single one. > > > But I am not talking about the computations that we (perhaps) observe. I > am talking about the computations which exist in arithmetic. So you're talking about computations that no machine and no person has ever performed or even observed, and calculations for which there is no evidence that they exist at all. 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 [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.
