Theorem bj-exexbiex

Description: Adding a second quantifier over the same variable is a transparent operation, ( E. E. case). (Contributed by BJ, 20-Oct-2019)

	Ref	Expression
Assertion	bj-exexbiex	$$⊢\exists x\exists x\phi \leftrightarrow \exists x\phi$$

Proof

Step	Hyp	Ref	Expression
1		nfe1	$$⊢Ⅎx\exists x\phi$$
2	1	19.9	$$⊢\exists x\exists x\phi \leftrightarrow \exists x\phi$$