Theorem spcegvOLD

Description: Obsolete version of spcegv as of 25-Aug-2023. (Contributed by NM, 14-Aug-1994) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypothesis	spcgv.1	$$⊢x=A\to \left(\phi \leftrightarrow \psi \right)$$
Assertion	spcegvOLD	$$⊢A\in V\to \left(\psi \to \exists x\phi \right)$$

Proof

Step	Hyp	Ref	Expression
1		spcgv.1	$$⊢x=A\to \left(\phi \leftrightarrow \psi \right)$$
2		nfcv	$$⊢\underset{\_}{Ⅎ}xA$$
3		nfv	$$⊢Ⅎx\psi$$
4	2 3 1	spcegf	$$⊢A\in V\to \left(\psi \to \exists x\phi \right)$$