Theorem pm2.67-2 888

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 863	. 2 ⊢ (𝜑 → (𝜑 ∨ 𝜒))
2	1	imim1i 63	1 ⊢ (((𝜑 ∨ 𝜒) → 𝜓) → (𝜑 → 𝜓))

Syntax hints:   → wi 4   ∨ wo 843

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 206  df-or 844

This theorem is referenced by:  pm2.67  889  jaob  958