Metamath Proof Explorer

Theorem chvarv

Description: Implicit substitution of y for x into a theorem. Usage of this theorem is discouraged because it depends on ax-13 . Use the weaker chvarvv if possible. (Contributed by NM, 20-Apr-1994) (Proof shortened by Wolf Lammen, 22-Apr-2018) (New usage is discouraged.)

Ref Expression
Hypotheses chvarv.1 x = y φ ψ
chvarv.2 φ
Assertion chvarv ψ


Step Hyp Ref Expression
1 chvarv.1 x = y φ ψ
2 chvarv.2 φ
3 nfv x ψ
4 3 1 2 chvar ψ