Theorem notnotri 125

Description: Inference associated with notnotr 124. (Contributed by NM, 27-Feb-2008.) (Proof shortened by Wolf Lammen, 15-Jul-2021.)

Hypothesis

Ref	Expression
notnotri.1	⊢ ¬ ¬ 𝜑

Assertion

Ref	Expression
notnotri	⊢ 𝜑

Proof of Theorem notnotri

Step	Hyp	Ref	Expression
1		notnotri.1	. . 3 ⊢ ¬ ¬ 𝜑
2	1	pm2.21i 115	. 2 ⊢ (¬ 𝜑 → 𝜑)
3	2	pm2.18i 122	1 ⊢ 𝜑

Syntax hints:  ¬ wn 3

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem is referenced by:  mt3  191  pm2.65ni  38235