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Constructive dilemma〔Hurley, Patrick. A Concise Introduction to Logic With Ilrn Printed Access Card. Wadsworth Pub Co, 2008. Page 361〕〔Moore and Parker〕〔Copi and Cohen〕 is a name of a valid rule of inference of propositional logic. It is the inference that, if ''P'' implies ''Q'' and ''R'' implies ''S'' and either ''P'' or ''R'' is true, then ''Q or S'' has to be true. In sum, if two conditionals are true and at least one of their antecedents is, then at least one of their consequents must be too. ''Constructive dilemma'' is the disjunctive version of modus ponens, whereas, destructive dilemma is the disjunctive version of ''modus tollens''. The rule can be stated: : where the rule is that whenever instances of "", "", and "" appear on lines of a proof, "" can be placed on a subsequent line. == Formal notation == The ''constructive dilemma'' rule may be written in sequent notation: : where is a metalogical symbol meaning that is a syntactic consequence of , , and in some logical system; and expressed as a truth-functional tautology or theorem of propositional logic: : where , , and are propositions expressed in some formal system. 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「constructive dilemma」の詳細全文を読む スポンサード リンク
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