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Theorem pm2.01 160
Description: Reductio ad absurdum. Theorem *2.01 of [WhiteheadRussell] p. 100. (Contributed by NM, 18-Aug-1993.) (Proof shortened by O'Cat, 21-Nov-2008.) (Proof shortened by Wolf Lammen, 31-Oct-2012.)
Assertion
Ref Expression
pm2.01 ((φ → ¬ φ) → ¬ φ)

Proof of Theorem pm2.01
StepHypRef Expression
1 id 19 . 2 φ → ¬ φ)
21, 1ja 153 1 ((φ → ¬ φ) → ¬ φ)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem is referenced by:  bijust  175  pm4.8  354
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