Theorem nexr

Description: Inference associated with the contrapositive of 19.8a . (Contributed by Jeff Hankins, 26-Jul-2009)

	Ref	Expression
Hypothesis	nexr.1	⊢ ¬ ∃ 𝑥 𝜑
Assertion	nexr	⊢ ¬ 𝜑

Proof

Step	Hyp	Ref	Expression
1		nexr.1	⊢ ¬ ∃ 𝑥 𝜑
2		19.8a	⊢ ( 𝜑 → ∃ 𝑥 𝜑 )
3	1 2	mto	⊢ ¬ 𝜑