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In logic, negation, also called logical complement, is an operation that takes a proposition ''p'' to another proposition "not ''p''", written ''¬p'', which is interpreted intuitively as being true when ''p'' is false and false when ''p'' is true. Negation is thus a unary (single-argument) logical connective. It may be applied as an operation on propositions, truth values, or semantic values more generally. In classical logic, negation is normally identified with the truth function that takes ''truth'' to ''falsity'' and vice versa. In intuitionistic logic, according to the Brouwer–Heyting–Kolmogorov interpretation, the negation of a proposition ''p'' is the proposition whose proofs are the refutations of ''p''. ==Definition== No agreement exists as to the possibility of defining negation, as to its logical status, function, and meaning, as to its field of applicability..., and as to the interpretation of the negative judgment, (F.H. Heinemann 1944). ''Classical negation'' is an operation on one logical value, typically the value of a proposition, that produces a value of ''true'' when its operand is false and a value of ''false'' when its operand is true. So, if statement ''A'' is true, then ''¬A'' (pronounced "not A") would therefore be false; and conversely, if ''¬A'' is true, then ''A'' would be false. The truth table of ''¬p'' is as follows: Classical negation can be defined in terms of other logical operations. For example, ¬''p'' can be defined as ''p'' → ''F'', where "→" is logical consequence and ''F'' is absolute falsehood. Conversely, one can define ''F'' as ''p'' & ¬''p'' for any proposition ''p'', where "&" is logical conjunction. The idea here is that any contradiction is false. While these ideas work in both classical and intuitionistic logic, they do not work in Brazilian logic, where contradictions are not necessarily false. But in classical logic, we get a further identity: ''p'' → ''q'' can be defined as ¬''p'' ∨ ''q'', where "∨" is logical disjunction: "not ''p'', or ''q''". Algebraically, classical negation corresponds to complementation in a Boolean algebra, and intuitionistic negation to pseudocomplementation in a Heyting algebra. These algebras provide a semantics for classical and intuitionistic logic respectively. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「negation」の詳細全文を読む スポンサード リンク
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