Theorem pm2.26

Description: Theorem *2.26 of WhiteheadRussell p. 104. See pm2.27 . (Contributed by NM, 3-Jan-2005) (Proof shortened by Wolf Lammen, 23-Nov-2012)

	Ref	Expression
Assertion	pm2.26	⊢ ( ¬ 𝜑 ∨ ( ( 𝜑 → 𝜓 ) → 𝜓 ) )

Proof

Step	Hyp	Ref	Expression
1		pm2.27	⊢ ( 𝜑 → ( ( 𝜑 → 𝜓 ) → 𝜓 ) )
2	1	imori	⊢ ( ¬ 𝜑 ∨ ( ( 𝜑 → 𝜓 ) → 𝜓 ) )