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|    Message 262,701 of 262,912    |
|    olcott to Mikko    |
|    Re: The Halting Problem asks for too muc    |
|    24 Jan 26 08:01:52    |
      XPost: sci.math, comp.theory       From: polcott333@gmail.com              On 1/24/2026 2:20 AM, Mikko wrote:       > On 23/01/2026 12:22, olcott wrote:       >> On 1/23/2026 3:13 AM, Mikko wrote:       >>> On 22/01/2026 18:40, olcott wrote:       >>>> On 1/22/2026 2:21 AM, Mikko wrote:       >>>>> On 21/01/2026 17:22, olcott wrote:       >>>>>> On 1/21/2026 3:03 AM, Mikko wrote:       >>>>>>>       >>>>>>> No, it hasn't. In the way theories are usually discussed nothing is       >>>>>>> "ture in arithmetic". Every sentence of a first order theory that       >>>>>>> can be proven in the theory is true in every model theory. Every       >>>>>>> sentence of a theory that cannot be proven in the theory is false       >>>>>>> in some model of the theory.       >>>>>>>       >>>>>>>> only because back then proof theoretic semantics did       >>>>>>>> not exist.       >>>>>>>       >>>>>>> Every interpretation of the theory is a definition of semantics.       >>>>>>>       >>>>>>       >>>>>> Meta‑math relations about numbers don’t exist in PA       >>>>>> because PA only contains arithmetical relations—addition,       >>>>>> multiplication, ordering, primitive‑recursive predicates       >>>>>> about numbers themselves—while relations that talk about       >>>>>> PA’s own proofs, syntax, or truth conditions live entirely       >>>>>> in the meta‑theory;       >>>>>       >>>>> Methamathematics does not need any other relations between numbers       >>>>> than what PA has. But relations that map other things to numbers       >>>>> can be useful for methamathematical purposes.       >>>>>       >>>>>> so when someone appeals to a Gödel‑style relation like       >>>>>> “n encodes a proof of this very sentence,” they’re       >>>>>> invoking a meta‑mathematical predicate that PA cannot       >>>>>> internalize, which is exactly why your framework draws       >>>>>> a clean boundary between internal proof‑theoretic truth       >>>>>> and external model‑theoretic truth.       >>>>>       >>>>> Anyway, what can be provven that way is true aboout PA. You can deny       >>>>> the proof but you cannot perform what is meta-provably impossible.       >>>>       >>>> Gödel’s sentence is not “true in arithmetic.”       >>>> It is true only in the meta‑theory, under an       >>>> external interpretation of PA (typically the       >>>> standard model ℕ). Inside PA itself, the sentence       >>>> is not a truth‑bearer at all.       >>>       >>> There is no concept of "truth-bearer" in an uninterpreted theory because       >>> there is not concept of "truth". The relevant concept is "sell-formed-       >>> formula" and Gödels sentence is one. It may be true or false in an       >>> interpretation.       >       >> There is a       >> "true on the basis of meaning expressed in language"       >> and I figured out how to make it computable over the       >> body of knowledge.       >       > Except that "true on the basis of meaning expressed in language" is       > nmt computable and does not cover all of the body of knowldge.       >              When the basis of "true" is proof theoretic semantics       internal to the formal system relative to its own axioms       and not truth conditional in a separate model outside       of the system undecidability ceases to exist.              --       Copyright 2026 Olcott |
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