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Metamath Proof Explorer

Theorem conax1

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

		Ref	Expression
	Assertion	conax1	$⊢ \neg (φ \to ψ) \to \neg ψ$

Step	Hyp	Ref	Expression
1		ax-1	$⊢ ψ \to (φ \to ψ)$
2	1	con3i	$⊢ \neg (φ \to ψ) \to \neg ψ$