Theorem idn1

Description: Virtual deduction identity rule which is id with virtual deduction symbols. (Contributed by Alan Sare, 24-Jun-2011) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	idn1	|- (. ph ->. ph ).

Proof

Step	Hyp	Ref	Expression
1		id	|- ( ph -> ph )
2	1	dfvd1ir	|- (. ph ->. ph ).