Theorem pm2.24

Description: Theorem *2.24 of WhiteheadRussell p. 104. Its associated inference is pm2.24i . Commuted form of pm2.21 . (Contributed by NM, 3-Jan-2005)

	Ref	Expression
Assertion	pm2.24	⊢ ( 𝜑 → ( ¬ 𝜑 → 𝜓 ) )

Proof

Step	Hyp	Ref	Expression
1		pm2.21	⊢ ( ¬ 𝜑 → ( 𝜑 → 𝜓 ) )
2	1	com12	⊢ ( 𝜑 → ( ¬ 𝜑 → 𝜓 ) )