Theorem idn2

Description: Virtual deduction identity rule which is idd with virtual deduction symbols. (Contributed by Alan Sare, 21-Apr-2011) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	idn2	$$⊢\left(\phi ,\psi \to \psi \right)$$

Proof

Step	Hyp	Ref	Expression
1		idd	$$⊢\phi \to \left(\psi \to \psi \right)$$
2	1	dfvd2ir	$$⊢\left(\phi ,\psi \to \psi \right)$$