Talk:Modus tollendo ponens

Perhaps I'm confused, but doesn't this rule apply to disjunctions? There is an old version of the article that seems more correct. Also, as far as I can tell, the schema "-A & (-A -> B) -> B" does not express the application of a rule. 67.171.140.29 10:20, 4 October 2007 (UTC)

The proposition given above is valid, but neither Modus Tollendo Ponens nor does it express a rule of inference. The external link on the Wikipedia page, "Disjunctive Syollogism" gives the actual rule, MTP. I am not familliar with Wikipedia; so, I will not edit this page, but it needs to be done. 134.10.6.37 19:36, 4 October 2007 (UTC)


 * Well no, it really is a rule of inference. It may not be a popular one, and it may be similar to disjunctive syllogism, but it is a different one and still a rule of inference. Greg Bard 21:18, 4 October 2007 (UTC)


 * I made an account so as not to confuse. The two unsigned comments, above, are mine.  The rule of inference, Modus Tollendo Ponens is a disjunctive syllogism.  The rule would apply as follows:


 * P or Q
 * Not P
 * Therefore, Q


 * It is well accounted for that the above pattern of inference is Modus Tollendo Ponens. The website linked from the disjunctive syllogism Wiki. article (http://logik.phl.univie.ac.at/~chris/beispielskriptum/node7.html), page 65 of Patrick Suppes and Shirley A. Hill's "First Course in Mathematical Logic" (a scan of which is available from Google Booksearch), and page 61 of E.J. Lemmon's "Beginning Logic" all support the claim that Modus Tollendo Ponens is the rule I expressed several lines above.


 * The Modus Tollendo Ponens article revision as of the 22nd of May 2005 matches with what I have said. If there is no objection, I think a revert is in order. Threepenpals 23:24, 4 October 2007 (UTC)