nnexmid - Mathbox for BJ

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Theorem nnexmid 9899

Description: Double negation of excluded middle. Intuitionistic logic refutes the negation of excluded middle (but, of course, does not prove excluded middle) for any formula. (Contributed by BJ, 9-Oct-2019.)

**Assertion**
Ref	Expression
nnexmid	$\/$

**Proof of Theorem nnexmid**
Step	Hyp	Ref	Expression
1		pm3.24 627	. 2 $/\$
2		ioran 669	. 2 $\/$ $/\$
3	1, 2	mtbir 596	1 $\/$

Colors of variables: wff set class

Syntax hints:

wn 3 $/\$ wa 97 $\/$ wo 629

This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 99 ax-ia2 100 ax-ia3 101 ax-in1 544 ax-in2 545 ax-io 630

This theorem depends on definitions: df-bi 110

This theorem is referenced by: nndc 9900

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