Category:Law of Excluded Middle

This category contains pages concerning Law of Excluded Middle:

The law of (the) excluded middle is a valid argument in certain types of logic dealing with disjunction $\lor$ and negation $\neg$.

This includes classical propositional logic and predicate logic, and in particular natural deduction, but for example not intuitionistic propositional logic.

Proof Rule

$\phi \lor \neg \phi$ for all statements $\phi$.

Sequent Form

The Law of Excluded Middle can be symbolised by the sequent:

$\vdash p \lor \neg p$