Theorem pm5.5

Description: Theorem *5.5 of WhiteheadRussell p. 125. (Contributed by NM, 3-Jan-2005)

	Ref	Expression
Assertion	pm5.5	⊢ ( 𝜑 → ( ( 𝜑 → 𝜓 ) ↔ 𝜓 ) )

Proof

Step	Hyp	Ref	Expression
1		biimt	⊢ ( 𝜑 → ( 𝜓 ↔ ( 𝜑 → 𝜓 ) ) )
2	1	bicomd	⊢ ( 𝜑 → ( ( 𝜑 → 𝜓 ) ↔ 𝜓 ) )