Theorem pm2.68 914

Description: Theorem *2.68 of [WhiteheadRussell] p. 108. (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
pm2.68	⊢ (((𝜑 → 𝜓) → 𝜓) → (𝜑 ∨ 𝜓))

Proof of Theorem pm2.68

Step	Hyp	Ref	Expression
1		jarl 126	. 2 ⊢ (((𝜑 → 𝜓) → 𝜓) → (¬ 𝜑 → 𝜓))
2	1	orrd 877	1 ⊢ (((𝜑 → 𝜓) → 𝜓) → (𝜑 ∨ 𝜓))

This proof depends on syntax axioms:   → wi 4   ∨ wo 861

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This proof depends on definitions:  df-bi 210  df-or 862

This theorem is used by:  dfor2  915