Theorem idd

Description: Principle of identity id with antecedent. (Contributed by NM, 26-Nov-1995)

	Ref	Expression
Assertion	idd	⊢ ( 𝜑 → ( 𝜓 → 𝜓 ) )

Proof

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