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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 Ref
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'.
22435 | The logician's '→' does not mean the English if-then [Quine] |
9512 | We write the 'negation' of P (not-P) as ¬ [Lemmon] |
9511 | We write the conditional 'if P (antecedent) then Q (consequent)' as P→Q [Lemmon] |
9508 | The sign |- may be read as 'therefore' [Lemmon] |
9509 | That proposition that both P and Q is their 'conjunction', written P∧Q [Lemmon] |
9510 | That proposition that either P or Q is their 'disjunction', written P∨Q [Lemmon] |
9513 | We write 'P if and only if Q' as P↔Q; it is also P iff Q, or (P→Q)∧(Q→P) [Lemmon] |
9514 | If A and B are 'interderivable' from one another we may write A -||- B [Lemmon] |
12005 | The symbol 'ι' forms definite descriptions; (ιx)F(x) says 'the x which is such that F(x)' [Forbes,G] |
7799 | Proposition logic has definitions for its three operators: or, and, and identical [Girle] |