From jjllambias2000@yahoo.com.ar Fri Jul 30 09:41:19 2004 Received: with ECARTIS (v1.0.0; list lojban-list); Fri, 30 Jul 2004 09:41:20 -0700 (PDT) Received: from web41908.mail.yahoo.com ([66.218.93.159]) by chain.digitalkingdom.org with smtp (Exim 4.32) id 1BqaRS-0003yr-RZ for lojban-list@lojban.org; Fri, 30 Jul 2004 09:41:11 -0700 Message-ID: <20040730164040.19871.qmail@web41908.mail.yahoo.com> Received: from [200.49.74.2] by web41908.mail.yahoo.com via HTTP; Fri, 30 Jul 2004 09:40:40 PDT Date: Fri, 30 Jul 2004 09:40:40 -0700 (PDT) From: Jorge "Llambías" Subject: [lojban] Re: jimpe To: lojban-list@lojban.org In-Reply-To: <20040730154526.GA3982@mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-archive-position: 8363 X-ecartis-version: Ecartis v1.0.0 Sender: lojban-list-bounce@lojban.org Errors-to: lojban-list-bounce@lojban.org X-original-sender: jjllambias2000@yahoo.com.ar Precedence: bulk Reply-to: lojban-list@lojban.org X-list: lojban-list --- Rob Speer 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 __________________________________ Do you Yahoo!? New and Improved Yahoo! Mail - Send 10MB messages! http://promotions.yahoo.com/new_mail