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Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: Mikko <mikko.levanto@iki.fi> Newsgroups: sci.logic Subject: Re: Simple enough for every reader? Date: Sat, 31 May 2025 12:59:27 +0300 Organization: - Lines: 39 Message-ID: <101ejtv$129q7$1@dont-email.me> References: <100a8ah$ekoh$1@dont-email.me> <100ccrl$upk6$1@dont-email.me> <100cjat$vtec$1@dont-email.me> <100fdbr$1laaq$1@dont-email.me> <100funo$1ous9$1@dont-email.me> <100haco$24mti$1@dont-email.me> <100hocb$2768i$1@dont-email.me> <100mpm7$3csuv$1@dont-email.me> <100much$3drk8$1@dont-email.me> <100p8v7$k2$1@dont-email.me> <100pbot$dmi$1@dont-email.me> <100rv2t$jpca$1@dont-email.me> <100sajh$lkp7$2@dont-email.me> <100us6p$1b4q2$1@dont-email.me> <100uvfe$1b4dh$3@dont-email.me> <1011fkf$1v4kb$1@dont-email.me> <1011qrn$20v83$1@dont-email.me> <10149ic$2jtva$1@dont-email.me> <1014kja$2l9jj$4@dont-email.me> <1016h9p$35it9$1@dont-email.me> <101797i$39rdb$1@dont-email.me> <1019bki$3qe6q$1@dont-email.me> <1019s2k$3sv8u$3@dont-email.me> <101bu77$dqtr$1@dont-email.me> <101cf4h$gl20$2@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Sat, 31 May 2025 11:59:27 +0200 (CEST) Injection-Info: dont-email.me; posting-host="bd1cfc1e45b4e90432c7d9e9043b3f3e"; logging-data="1124167"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+A7fBlEGXMv4gIIgdilgdt" User-Agent: Unison/2.2 Cancel-Lock: sha1:edNe94E7Vy+Zt08zDjBijIUUm9Q= On 2025-05-30 14:25:22 +0000, WM said: > On 30.05.2025 11:36, Mikko wrote: >> On 2025-05-29 14:47:49 +0000, WM said: >> >>>> It is in certain mathematical structures but not in all. >>> >>> Anyhow a reader in sci.logic should understand it. >> >> Everybody should understand at least arithmetic induction and its >> limitations. But everybody doesn't. > > "Not everybody does" would be correct. >> >> Cantor did not use ℵo for infinity in general but only for a particular >> kind of infinity. > > For all infinite sets of natural numbers he used it. That's what I > discuss here. Only after proving that all infinite subsetssets of the set of natural numbers are equinumerous. >>> P[n]: {1, 2, 3, ..., n} has infinitely many (ℵo) successors. >>> P[n+1]: {1, 2, 3, ..., n, n+1} has infinitely many (ℵo) successors. >> >> But P[n] -> P[n+1] is not there. >> >>> Do you doubt ℵo - 1 = ℵo? >> >> That can't be said in Peano arithmetic. > > Here I use induction in Cantor's set. That is allowed. Cantor did it too. No, there is no artithmetic induction and no set induction there. -- Mikko