Path: ...!news.tomockey.net!3.eu.feeder.erje.net!feeder.erje.net!news.szaf.org!news.karotte.org!news.space.net!news.muc.de!.POSTED.news.muc.de!not-for-mail From: Alan Mackenzie Newsgroups: sci.logic,comp.theory Subject: Re: Formal systems that cannot possibly be incomplete except for unknowns and unknowable Followup-To: comp.theory Date: Tue, 6 May 2025 08:17:46 -0000 (UTC) Organization: muc.de e.V. Message-ID: References: Injection-Date: Tue, 6 May 2025 08:17:46 -0000 (UTC) Injection-Info: news.muc.de; posting-host="news.muc.de:2001:608:1000::2"; logging-data="65292"; mail-complaints-to="news-admin@muc.de" User-Agent: tin/2.6.4-20241224 ("Helmsdale") (FreeBSD/14.2-RELEASE-p1 (amd64)) Bytes: 3093 Lines: 54 [ Followup-To: set ] In comp.theory olcott wrote: > On 5/5/2025 10:31 AM, olcott wrote: >> On 5/5/2025 6:04 AM, Richard Damon wrote: >>> On 5/4/25 10:23 PM, olcott wrote: >>>> When we define formal systems as a finite list of basic facts and >>>> allow semantic logical entailment as the only rule of inference we >>>> have systems that can express any truth that can be expressed in >>>> language. Including the existence of undecidable statements. That is a truth in _any_ logical system bar the simplest or inconsistent ones. >>>> Also with such systems Undecidability is impossible. The only >>>> incompleteness are things that are unknown or unknowable. >>> Can such a system include the mathematics of the natural numbers? >>> If so, your claim is false, as that is enough to create that >>> undeciability. >> It seems to me that the inferences steps that could >> otherwise create undecidability cannot exist in the >> system that I propose. > The mathematics of natural numbers (as I have already explained) > begins with basic facts about natural numbers and only applies > truth preserving operations to these basic facts. > When we begin with truth and only apply truth preserving > operations then WE NECESSARILY MUST END UP WITH TRUTH. You will necessarily end up with only a subset of truth, no matter how shouty you are in writing it. You'll also end up with undecidability, no matter how hard you try to pretend it isn't there. > When we ALWAYS end up with TRUTH then we NEVER end up with UNDECIDABILITY. Shut your eyes, and you won't see it. > Its not that hard, iff you pay enough attention. It's too hard for you. As I've already suggested in another post, you'd do better to show some respect to those who understand the matters you're dabbling in. Accept that your level of understanding is not particularly high, and _learn_ from these other people. > -- > Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius > hits a target no one else can see." Arthur Schopenhauer -- Alan Mackenzie (Nuremberg, Germany).