more from GE Hughes/M Cresswell

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Single Idea 9541

[catalogued under 4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / d. Basic theorems of PL]

Full Idea

The Law of Transposition says that (P→Q) → (¬Q→¬P).

Gist of Idea

The Law of Transposition says (P→Q) → (¬Q→¬P)

Source

GE Hughes/M Cresswell (An Introduction to Modal Logic [1968], Ch.1)

Book Reference

Hughes,G./Cresswell,M.: 'An Introduction to Modal Logic' [Methuen 1972], p.15

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A Reaction

That is, if the consequent (Q) of a conditional is false, then the antecedent (P) must have been false.