[sci.philosophy.tech] Corrigendum to: Re: Unbelievable but true...

kube@cogsci.berkeley.edu (Paul Kube) (05/29/87)

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