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Metamath Proof Explorer

Theorem pm5.14

Description: Theorem *5.14 of WhiteheadRussell p. 123. (Contributed by NM, 3-Jan-2005)

		Ref	Expression
	Assertion	pm5.14	$⊢ ((φ \to ψ) \lor (ψ \to χ))$

Step	Hyp	Ref	Expression
1		pm2.521g	$⊢ \neg (φ \to ψ) \to (ψ \to χ)$
2	1	orri	$⊢ ((φ \to ψ) \lor (ψ \to χ))$