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Metamath Proof Explorer

Theorem pm2.68

Description: Theorem *2.68 of WhiteheadRussell p. 108. (Contributed by NM, 3-Jan-2005)

		Ref	Expression
	Assertion	pm2.68	$⊢ ((φ \to ψ) \to ψ) \to (φ \lor ψ)$

Step	Hyp	Ref	Expression
1		jarl	$⊢ ((φ \to ψ) \to ψ) \to (\neg φ \to ψ)$
2	1	orrd	$⊢ ((φ \to ψ) \to ψ) \to (φ \lor ψ)$