axfrege31 - Mathbox for Richard Penner

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Theorem axfrege31 43824

Description: Identical to notnotr 130. Axiom 31 of [Frege1879] p. 44. (Contributed by RP, 24-Dec-2019.)

**Assertion**
Ref	Expression
axfrege31	⊢ (¬ ¬ 𝜑 → 𝜑)

**Proof of Theorem axfrege31**
Step	Hyp	Ref	Expression
1		notnotr 130	1 ⊢ (¬ ¬ 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: (None)