Theorem pm2.67-2 391

Description: Slight generalization of Theorem *2.67 of [WhiteheadRussell] p. 107. (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
pm2.67-2	⊢ (((φ ∨ χ) → ψ) → (φ → ψ))

Proof of Theorem pm2.67-2

Step	Hyp	Ref	Expression
1		orc 374	. 2 ⊢ (φ → (φ ∨ χ))
2	1	imim1i 54	1 ⊢ (((φ ∨ χ) → ψ) → (φ → ψ))

Syntax hints:   → wi 4   ∨ wo 357

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem depends on definitions:  df-bi 177  df-or 359

This theorem is referenced by:  pm2.67  392  jaob  758