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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.)
Ref Expression

Proof of Theorem exmid
StepHypRef Expression
1 id 19 . 2
21orri 365 1
Colors of variables: wff setvar class
Syntax hints:   wn 3   wo 357
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 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  2522  rabxm  3573  elimif  3691
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