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Axiom ax-in1 577
Description: 'Not' introduction. One of the axioms of propositional 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  579  notnotsnex  3985
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