Message-ID: <20040730164040.19871.qmail@web41908.mail.yahoo.com>
Date: Fri, 30 Jul 2004 09:40:40 -0700 (PDT)
In-Reply-To: <20040730154526.GA3982@mit.edu>
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From: Jorge "Llambías" <jjllambias2000@yahoo.com.ar>
Reply-To: jjllambias2000@yahoo.com.ar
Subject: [lojban] Re: jimpe
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--- Rob Speer <rspeer@MIT.EDU> wrote:
> On Fri, Jul 30, 2004 at 11:17:27AM -0400, MorphemeAddict@wmconnect.com wrote:
> > That is *so* cool.  But is the logic in the first example (section 4.1) 
> > valid?  It seems to be deducing a premise from a consequence, which I've
> always 
> > thought was a big no-no.  And then  "artificial" in the title.  
> 
> Unless I'm completely screwing something up, it's deducing the _negation_ of
> a
> premise from the _negation_ of a consequence, which is perfectly valid logic.
> It's called "modus tollens" or the "rule of the contrapositive".

There's nothing wrong with the logic. The use of "premise" here
is not standard though. An implication has an antecedent and a
consequent, a logical argument has premises and conclusion.

In a modus tollens type of argument, one of the premises is an 
implication and the other premise is the negation of the consequent 
of that implication. From those two premises, it is valid to 
conclude the negation of the antecedent of the implication.

mu'o mi'e xorxes
 

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