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I am doing some discrete math here. Say if I have something like "NOT k", if I add another "NOT" in front of it to make it "NOT NOT k" would the two "NOT" cancel out to simply become just "k"?

Would this hold true for sentences as well? It's a weird logic thing that I'm having a hard time getting a grasp on.

halfer
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Vimzy
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  • http://en.wikipedia.org/wiki/Negation#Double_negation – user2864740 May 14 '14 at 21:49
  • I have never heard of "not not" used in [English] "sentences" (except when describing non-idiomatic constructs or weasel speak), although there are many other ways to say not that/those nots. If you have a problem with a *specific* sentence/question phrasing, then ask that. And please take a moment to perform cursory research. – user2864740 May 14 '14 at 21:51

3 Answers3

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To understand this from a more formal point of view don't not take a look at https://en.wikipedia.org/wiki/Double_negation.

Note that although most logical systems assume the validity of double negation elimination, that is not universally the case.

MattClarke
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Yes. Chaining two NOT operators together just returns the original k. A single NOT flips the value from true to false or false to true. The second one flips it back.

recursive
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When you negate a value, you find it's inverse. So what's the inverse of an inverse? Negating something twice will always result in the original value.

So in your example, NOT NOT k == k.

James Alexander
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  • Okay, on a related side note. S or not T, S, Thus not T (would this represent disjunctive syllogism?) – Vimzy May 14 '14 at 21:55