Theorem pm2.68

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

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

Proof

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