Path: news.cambrium.nl!textnews.cambrium.nl!feeder1.cambriumusenet.nl!feed.tweaknews.nl!209.197.12.246.MISMATCH!nx02.iad01.newshosting.com!newshosting.com!news.glorb.com!postnews.google.com!news2.google.com!npeer01.iad.highwinds-media.com!news.highwinds-media.com!feed-me.highwinds-media.com!spln!extra.newsguy.com!newsp.newsguy.com!drn From: stevendaryl3016@yahoo.com (Daryl McCullough) Newsgroups: comp.databases.theory,sci.logic,sci.philosophy.tech Subject: Re: Fitch's paradox and OWA Date: 31 Dec 2009 20:26:16 -0800 Organization: NewsGuy - Unlimited Usenet $19.95 Lines: 30 Message-ID: References: <4919dc70-6375-432e-b2aa-2f7c1b3c15ba@n31g2000vbt.googlegroups.com> <736f25ee-d0d4-4c10-807a-247776181f8e@h9g2000yqa.googlegroups.com> NNTP-Posting-Host: p5b55fe6a465ee8754c3c113f6c13ca51400b34f3d089ebf3.newsdawg.com User-Agent: Direct Read News 5.16 Xref: news.cambrium.nl sci.logic:158599 comp.databases.theory:38096 Marshall says... >However what I was referring to was specifically >how they get from step 7 to step 8 within that >RAA proof. Your response does not seem to >address that particular issue. That's exactly the step that I was talking about. Steps (4), (5) and (6) and (7) constitute a proof of ~K(p ∧ ~Kp). Therefore, we have |- ~K(p ∧ ~Kp) By C, if you have |- f, then you have |- [] f. Letting f = ~K(p ∧ ~Kp), it follows that |- [] ~K(p ∧ ~Kp) which is step (8). >Are your comfortable with how step 8 is >obtained from step 7 via Rule C as described >on this page? >http://plato.stanford.edu/entries/fitch-paradox/ Yes, that's exactly what they are doing. They didn't use the |- symbol in step 7, but it is clear that (7) is the conclusion of a proof. -- Daryl McCullough Ithaca, NY