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Metamath Proof Explorer

Theorem pm5.41

Description: Theorem *5.41 of WhiteheadRussell p. 125. (Contributed by NM, 3-Jan-2005) (Proof shortened by Wolf Lammen, 12-Oct-2012)

		Ref	Expression
	Assertion	pm5.41	$⊢ ((φ \to ψ) \to (φ \to χ)) \leftrightarrow (φ \to (ψ \to χ))$

Step	Hyp	Ref	Expression
1		imdi	$⊢ (φ \to (ψ \to χ)) \leftrightarrow ((φ \to ψ) \to (φ \to χ))$
2	1	bicomi	$⊢ ((φ \to ψ) \to (φ \to χ)) \leftrightarrow (φ \to (ψ \to χ))$