Theorem orim2 814

Description: Axiom *1.6 (Sum) of [WhiteheadRussell] p. 97. (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
orim2	⊢ ((ψ → χ) → ((φ ∨ ψ) → (φ ∨ χ)))

Proof of Theorem orim2

Step	Hyp	Ref	Expression
1		id 19	. 2 ⊢ ((ψ → χ) → (ψ → χ))
2	1	orim2d 813	1 ⊢ ((ψ → χ) → ((φ ∨ ψ) → (φ ∨ χ)))

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  df-an 360

This theorem is referenced by:  pm2.81  824  rb-ax1  1517