# What do you infer from this sentence “X is not Y or Z”? [duplicate]

Possible Duplicate:
Is “not eating or drinking” equal to “not eating or not drinking”?

I am confused in inferring a sentence of pattern "X is not Y or Z".

Is it the same as "X is not Y or X is not Z" ?

OR

Is it the same as "X is not Y or X is Z" ?

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## marked as duplicate by J D OConal, Ralph Rickenbach, RegDwigнt♦, Mehper C. Palavuzlar, ssaklOct 13 '10 at 13:02

J D is correct, applying the rule of that post here states that "X is not Y or Z" corresponds to "X is not Y or X is not X". In symbolic logic where n corresponds to not, we have X=n(Y v Z) if and only if X=nY ^ nZ. This is referred to as one of De-Morgan's Laws. – BBischof Oct 13 '10 at 5:56
But "not X or Y" =/= not (X or Y), right? – xport Oct 13 '10 at 6:26
You can't use the rules of logic "and", "not, "or" to English. "Didn't you beat your wife?" "No!". The answerer is saying he did not beat his wife. If you used the negation from logic, the answerer would be denying he didn't, meaning he did. – R. Martinho Fernandes Oct 13 '10 at 9:55
Martinho is exactly right, and this is the reason for the confusion of your comment. Notice in my comment I use parenthesis. It is for exactly this reason! However, now I think you get the idea. – BBischof Oct 13 '10 at 18:51

``````"X is not Y or Z"