|
In propositional logic, transposition〔Moore and Parker〕 is a valid rule of replacement that permits one to switch the antecedent with the consequent of a conditional statement in a logical proof if they are also both negated. It is the inference from the truth of "''A'' implies ''B''" the truth of "Not-''B'' implies not-''A''", and conversely.〔Brody, Bobuch A. "Glossary of Logical Terms". ''Encyclopedia of Philosophy''. Vol. 5–6, p. 76. Macmillan, 1973.〕〔Copi, Irving M. ''Symbolic Logic''. 5th ed. Macmillan, 1979. See the Rules of Replacement, pp. 39-40.〕 It is very closely related to the rule of inference modus tollens. It is the rule that: Where "" is a metalogical symbol representing "can be replaced in a proof with." == Formal notation == The ''transposition'' rule may be expressed as a sequent: : where is a metalogical symbol meaning that is a syntactic consequence of in some logical system; or as a rule of inference: : where the rule is that wherever an instance of "" appears on a line of a proof, it can be replaced with ""; or as the statement of a truth-functional tautology or theorem of propositional logic. The principle was stated as a theorem of propositional logic by Russell and Whitehead in ''Principia Mathematica'' as: : 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「Transposition (logic)」の詳細全文を読む スポンサード リンク
|