Theorem n0i

Description: If a class has elements, then it is not empty. (Contributed by NM, 31-Dec-1993)

	Ref	Expression
Assertion	n0i	⊢ ( 𝐵 ∈ 𝐴 → ¬ 𝐴 = ∅ )

Proof

Step	Hyp	Ref	Expression
1		nel02	⊢ ( 𝐴 = ∅ → ¬ 𝐵 ∈ 𝐴 )
2	1	con2i	⊢ ( 𝐵 ∈ 𝐴 → ¬ 𝐴 = ∅ )