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Path: ...!2.eu.feeder.erje.net!feeder.erje.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: olcott <polcott333@gmail.com> Newsgroups: sci.logic Subject: Re: A different perspective on undecidability --- incorrect question Date: Tue, 22 Oct 2024 10:04:37 -0500 Organization: A noiseless patient Spider Lines: 53 Message-ID: <vf8eu5$1h5mj$2@dont-email.me> References: <veoift$29dtl$2@dont-email.me> <veoq3j$2aqp2$1@dont-email.me> <vf716u$1607j$1@dont-email.me> <vf7ks8$1d1vt$1@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Tue, 22 Oct 2024 17:04:38 +0200 (CEST) Injection-Info: dont-email.me; posting-host="0250fa4f333a237bb4a9bec06e6bd0e6"; logging-data="1611475"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1++Mwrtki7B2Y9TQqUCGYgo" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:AS+dRmwTfRyOI5tIy//jy6T0X0E= X-Antivirus: Norton (VPS 241022-2, 10/22/2024), Outbound message In-Reply-To: <vf7ks8$1d1vt$1@dont-email.me> Content-Language: en-US X-Antivirus-Status: Clean Bytes: 3272 On 10/22/2024 2:39 AM, Mikko wrote: > On 2024-10-22 02:04:14 +0000, olcott said: > >> On 10/16/2024 11:37 AM, Mikko wrote: >>> On 2024-10-16 14:27:09 +0000, olcott said: >>> >>>> The whole notion of undecidability is anchored in ignoring the fact >>>> that >>>> some expressions of language are simply not truth bearers. >>> >>> A formal theory is undecidable if there is no Turing machine that >>> determines whether a formula of that theory is a theorem of that >>> theory or not. Whether an expression is a truth bearer is not >>> relevant. Either there is a valid proof of that formula or there >>> is not. No third possibility. >>> >> >> After being continually interrupted by emergencies >> interrupting other emergencies... >> >> If the answer to the question: Is X a formula of theory Y >> cannot be determined to be yes or no then the question >> itself is somehow incorrect. > > There are several possibilities. > > A theory may be intentionally incomplete. For example, group theory > leaves several important question unanswered. There are infinitely > may different groups and group axioms must be true in every group. > > Another possibility is that a theory is poorly constructed: the > author just failed to include an important postulate. > > Then there is the possibility that the purpose of the theory is > incompatible with decidability, for example arithmetic. > >> An incorrect question is an expression of language that >> is not a truth bearer translated into question form. >> >> When "X a formula of theory Y" is neither true nor false >> then "X a formula of theory Y" is not a truth bearer. > > Whether AB = BA is not answered by group theory but is alwasy > true or false about specific A and B and universally true in > some groups but not all. > See my most recent reply to Richard it sums up my position most succinctly. -- Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius hits a target no one else can see." Arthur Schopenhauer