Theorem r19.3rzvOLD

Description: Obsolete version of r19.3rzv as of 16-Feb-2026. (Contributed by NM, 10-Mar-1997) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	r19.3rzvOLD	$$⊢A\ne \varnothing \to \left(\phi \leftrightarrow \forall x\in A\phi \right)$$

Proof

Step	Hyp	Ref	Expression
1		nfv	$$⊢Ⅎx\phi$$
2	1	r19.3rz	$$⊢A\ne \varnothing \to \left(\phi \leftrightarrow \forall x\in A\phi \right)$$