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Metamath Proof Explorer

Theorem conax1

Description: Contrapositive of ax-1 . (Contributed by BJ, 28-Oct-2023)

Ref Expression
Assertion conax1 ( ¬ ( 𝜑 → 𝜓 ) → ¬ 𝜓 )

Proof

Step Hyp Ref Expression
1 ax-1 ⊢ ( 𝜓 → ( 𝜑 → 𝜓 ) )
2 1 con3i ⊢ ( ¬ ( 𝜑 → 𝜓 ) → ¬ 𝜓 )