Single Idea 9533

[catalogued under 4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / b. Terminology of PL]

Full Idea

One proposition A 'implies' a proposition B if whenever A is true B is true (but not necessarily conversely), which is only the case if A→B is tautologous. Hence B 'is implied' by A.

Gist of Idea

A 'implies' B if B is true whenever A is true (so that A→B is tautologous)

Source

E.J. Lemmon (Beginning Logic [1965], 2.3)

Book Reference

Lemmon,E.J.: 'Beginning Logic' [Nelson 1979], p.70

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