Theorem vd01

Description: A virtual hypothesis virtually infers a theorem. (Contributed by Alan Sare, 14-Jun-2011) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypothesis	vd01.1	$$⊢\phi$$
Assertion	vd01	$$⊢\left(\psi \to \phi \right)$$

Proof

Step	Hyp	Ref	Expression
1		vd01.1	$$⊢\phi$$
2	1	a1i	$$⊢\psi \to \phi$$
3	2	dfvd1ir	$$⊢\left(\psi \to \phi \right)$$