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Theorem exmid 404

Description: Law of excluded middle, also called the principle of tertium non datur. Theorem *2.11 of [WhiteheadRussell] p. 101. It says that something is either true or not true; there are no in-between values of truth. This is an essential distinction of our classical logic and is not a theorem of intuitionistic logic. (Contributed by NM, 5-Aug-1993.)

**Assertion**
Ref	Expression
exmid	$\/$

**Proof of Theorem exmid**
Step	Hyp	Ref	Expression
1		id 19	. 2
2	1	orri 365	1 $\/$

Colors of variables: wff setvar class

Syntax hints:

wn 3 $\/$ wo 357

This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8

This theorem depends on definitions: df-bi 177 df-or 359

This theorem is referenced by: exmidd 405 pm5.62 889 pm5.63 890 pm4.83 895 4exmid 905 exmidne 2523 rabxm 3574 elimif 3692

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