more from E.J. Lemmon

---

Single Idea 9523

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

Full Idea

The forms of De Morgan's Laws [P∨Q -||- ¬(¬P ∧ ¬Q); ¬(P∨Q) -||- ¬P ∧ ¬Q; ¬(P∧Q) -||- ¬P ∨ ¬Q); P∧Q -||- ¬(¬P∨¬Q)] transform negated conjunctions and disjunctions into non-negated disjunctions and conjunctions respectively.

Gist of Idea

De Morgan's Laws make negated conjunctions/disjunctions into non-negated disjunctions/conjunctions

Source

E.J. Lemmon (Beginning Logic [1965], 2.2)

Book Reference

Lemmon,E.J.: 'Beginning Logic' [Nelson 1979], p.62

---