Theorem bj-nexrt

Description: Closed form of nexr . Contrapositive of 19.8a . (Contributed by BJ, 20-Oct-2019)

	Ref	Expression
Assertion	bj-nexrt	$$⊢\neg \exists x\phi \to \neg \phi$$

Proof

Step	Hyp	Ref	Expression
1		19.8a	$$⊢\phi \to \exists x\phi$$
2	1	con3i	$$⊢\neg \exists x\phi \to \neg \phi$$