Theorem 19.23bi

Description: Inference form of Theorem 19.23 of Margaris p. 90, see 19.23 . (Contributed by NM, 12-Mar-1993)

	Ref	Expression
Hypothesis	19.23bi.1	$$⊢\exists x\phi \to \psi$$
Assertion	19.23bi	$$⊢\phi \to \psi$$

Proof

Step	Hyp	Ref	Expression
1		19.23bi.1	$$⊢\exists x\phi \to \psi$$
2		19.8a	$$⊢\phi \to \exists x\phi$$
3	2 1	syl	$$⊢\phi \to \psi$$