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Theorem wl-pm2.21 32926
Description: From a wff and its negation, anything follows. Theorem *2.21 of [WhiteheadRussell] p. 104. Also called the Duns Scotus law. Copy of pm2.21 120 with a different proof. (Contributed by Wolf Lammen, 17-Dec-2018.) (New usage is discouraged.) (Proof modification is discouraged.)
Assertion
Ref Expression
wl-pm2.21 𝜑 → (𝜑𝜓))

Proof of Theorem wl-pm2.21
StepHypRef Expression
1 ax-luk3 32910 . 2 (𝜑 → (¬ 𝜑𝜓))
21wl-com12 32925 1 𝜑 → (𝜑𝜓))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4
This theorem was proved from axioms:  ax-mp 5  ax-luk1 32908  ax-luk2 32909  ax-luk3 32910
This theorem is referenced by:  wl-con1i  32927  wl-ax2  32931
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