Metamath Proof Explorer


Theorem axie1

Description: The setvar x is not free in E. x ph (intuitionistic logic axiom ax-ie1). (Contributed by Jim Kingdon, 31-Dec-2017) (New usage is discouraged.)

Ref Expression
Assertion axie1 x φ x x φ

Proof

Step Hyp Ref Expression
1 hbe1 x φ x x φ