Theorem pm2.04 76

Description: Swap antecedents. Theorem *2.04 of [WhiteheadRussell] p. 100. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Wolf Lammen, 12-Sep-2012.)

Assertion

Ref	Expression
pm2.04	⊢ ((φ → (ψ → χ)) → (ψ → (φ → χ)))

Proof of Theorem pm2.04

Step	Hyp	Ref	Expression
1		id 19	. 2 ⊢ ((φ → (ψ → χ)) → (φ → (ψ → χ)))
2	1	com23 72	1 ⊢ ((φ → (ψ → χ)) → (ψ → (φ → χ)))

Syntax hints:   → wi 4

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7

This theorem is referenced by:  com34  77  com45  83  bi2.04  350  merco2  1501  ralcom3  2777