Metamath Proof Explorer

Theorem axfrege58b

Description: If A. x ph is affirmed, [ y / x ] ph cannot be denied. Identical to stdpc4 . Justification for ax-frege58b . (Contributed by RP, 28-Mar-2020)

Ref Expression
Assertion axfrege58b 
|- ( A. x ph -> [ y / x ] ph )

Proof

Step Hyp Ref Expression
1 stdpc4 
 |-  ( A. x ph -> [ y / x ] ph )