Theorem biidd

Description: Principle of identity with antecedent. (Contributed by NM, 25-Nov-1995)

	Ref	Expression
Assertion	biidd	⊢ ( 𝜑 → ( 𝜓 ↔ 𝜓 ) )

Proof

Step	Hyp	Ref	Expression
1		biid	⊢ ( 𝜓 ↔ 𝜓 )
2	1	a1i	⊢ ( 𝜑 → ( 𝜓 ↔ 𝜓 ) )