more from E.J. Lemmon

### Single Idea 9534

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

Full Idea

Two propositions are 'equivalent' if whenever A is true B is true, and whenever B is true A is true, in which case A↔B is a tautology.

Gist of Idea

Two propositions are 'equivalent' if they mirror one another's truth-value

Source

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

Book Reference

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