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Theorem axfrege31 37644
Description: Identical to notnotr 125. Axiom 31 of [Frege1879] p. 44. (Contributed by RP, 24-Dec-2019.)
Assertion
Ref Expression
axfrege31 (¬ ¬ 𝜑𝜑)

Proof of Theorem axfrege31
StepHypRef Expression
1 notnotr 125 1 (¬ ¬ 𝜑𝜑)
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: (None)
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