Full Idea
The law of excluded middle says if a proposition is false, then its negation is true
Gist of Idea
If a proposition is false, then its negation is true
Source
James Robert Brown (Philosophy of Mathematics [1999], Ch. 1)
Book Reference
Brown,James Robert: 'Philosophy of Mathematics' [Routledge 2002], p.5
A Reaction
Surely that is the best statement of the law? How do you write that down? ¬(P)→¬P? No, because it is a semantic claim, not a syntactic claim, so a truth table captures it. Semantic claims are bigger than syntactic claims.