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From: kube@cogsci.berkeley.edu (Paul Kube)
Newsgroups: sci.philosophy.tech
Subject: Corrigendum to: Re: Unbelievable but true...
Message-ID: <19190@ucbvax.BERKELEY.EDU>
Date: Fri, 29-May-87 14:30:20 EDT
Article-I.D.: ucbvax.19190
Posted: Fri May 29 14:30:20 1987
Date-Received: Sun, 31-May-87 07:45:46 EDT
References: <1150@cavell.UUCP> <19097@ucbvax.BERKELEY.EDU>
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: kube@cogsci.berkeley.edu.UUCP (Paul Kube)
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Organization: University of California, Berkeley
Lines: 26
Keywords: epistemic logic modal logic


In article <19097@ucbvax.BERKELEY.EDU> kube@cogsci.berkeley.edu.UUCP (I) write:
>
>-L(P & -LP) (i.e., (x)(p)~Bel(x, p & ~Bel(x,p)) ) is a theorem in each of
>these systems.  You don't need LP -> LLP (which is missing from T),
>only LP -> P :
>
>1.      L(P & -LP)      (assume for contradiction)
>2.      P & -LP         (from 1. by LP -> P)
>3.      P               (from 2. by conjunction elimination)
>4.      LP              (from 3. by necessitation)
>5.      -LP             (from 2. by conjunction elimination)
>6.      LP & -LP        (from 4., 5.)

Well, actually, this only shows that L(P&-LP) can't be a theorem, 
not that -L(P&-LP) is.  I take it back.
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--Paul kube@berkeley.edu, ...!ucbvax!kube