Metamath Proof Explorer


Theorem nfe2

Description: An inner existential quantifier's variable is bound. (Contributed by SN, 11-Feb-2026)

Ref Expression
Assertion nfe2 x y x φ

Proof

Step Hyp Ref Expression
1 excom y x φ x y φ
2 nfe1 x x y φ
3 1 2 nfxfr x y x φ