Theorem 19.8w

Description: Weak version of 19.8a and instance of 19.2d . (Contributed by NM, 1-Aug-2017) (Proof shortened by Wolf Lammen, 4-Dec-2017) (Revised by BJ, 31-Mar-2021)

	Ref	Expression
Hypothesis	19.8w.1	$$⊢\phi \to \forall x\phi$$
Assertion	19.8w	$$⊢\phi \to \exists x\phi$$

Proof

Step	Hyp	Ref	Expression
1		19.8w.1	$$⊢\phi \to \forall x\phi$$
2	1	19.2d	$$⊢\phi \to \exists x\phi$$