Theorem bj-nexrt

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

	Ref	Expression
Assertion	bj-nexrt	⊢ ( ¬ ∃ 𝑥 𝜑 → ¬ 𝜑 )

Proof

Step	Hyp	Ref	Expression
1		19.8a	⊢ ( 𝜑 → ∃ 𝑥 𝜑 )
2	1	con3i	⊢ ( ¬ ∃ 𝑥 𝜑 → ¬ 𝜑 )