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Metamath Proof Explorer

Theorem pm2.42

Description: Theorem *2.42 of WhiteheadRussell p. 106. (Contributed by NM, 3-Jan-2005)

		Ref	Expression
	Assertion	pm2.42	$⊢ (\neg φ \lor (φ \to ψ)) \to (φ \to ψ)$

Step	Hyp	Ref	Expression
1		pm2.21	$⊢ \neg φ \to (φ \to ψ)$
2		id	$⊢ (φ \to ψ) \to (φ \to ψ)$
3	1 2	jaoi	$⊢ (\neg φ \lor (φ \to ψ)) \to (φ \to ψ)$