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Axiom ax-in1 526
Description: 'Not' introduction. Axiom 4 of 10 for intuitionistic logic. (Contributed by Mario Carneiro, 31-Jan-2015.)
Assertion
Ref Expression
ax-in1 ((φ → ¬ φ) → ¬ φ)

Detailed syntax breakdown of Axiom ax-in1
StepHypRef Expression
1 wph . . 3 wff φ
21wn 3 . . 3 wff ¬ φ
31, 2wi 4 . 2 wff (φ → ¬ φ)
43, 2wi 4 1 wff ((φ → ¬ φ) → ¬ φ)
Colors of variables: wff set class
This axiom is referenced by:  pm2.01  528
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