more from E.J. Lemmon

### Single Idea 9512

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

Full Idea

We write 'not-P' as ¬P. This is called the 'negation' of P. The 'double negation' of P (not not-P) would be written as ¬¬P.

Gist of Idea

We write the 'negation' of P (not-P) as ¬

Source

E.J. Lemmon (Beginning Logic [1965], 1.2)

Book Reference

Lemmon,E.J.: 'Beginning Logic' [Nelson 1979], p.7

A Reaction

Lemmons use of -P is no longer in use for 'not'. A tilde sign (squiggle) is also used for 'not', but some interpreters give that a subtly different meaning (involving vagueness). The sign ¬ is sometimes called 'hook' or 'corner'.