Talk:Double negative elimination
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The article states:
The rule of double negative introduction states the converse, that double negatives can be added without changing the meaning of a proposition.
This seems to be wrong. If we have only double negative introduction but not double negative elimination, then adding a double negative weakens the proposition. To me, this seems like changing the meaning.Punainen Nörtti 17:50, 18 May 2007 (UTC)
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- Yes, I think the proper wording would be "truth value", not "meaning". Otherwise double negative introduction would imply double negative elimination by equating the two propositions. — brighterorange (talk) 18:44, 18 May 2007 (UTC)
- Actually, I think that's not right either, since (A v ~A) is not provable in intuitionistic ("has no truth value"?) whereas its double negation does. I think there is a more global confusion in the article about whether A = ~~A or whether A ==> ~~A and/or ~~A ==> A as theorems of the logic. The latter seems to be the only sensible way to phrase it if we're going to talk about intuitionistic logic too. — brighterorange (talk) 18:46, 18 May 2007 (UTC)
