simp only [occursFreeIn] at h1
D : Type
I : Interpretation D
X : String
vs : List Var
V V' : VarAssignment D
h1 : ∀ (v : Var), occursFreeIn v (pred_ X vs) → V v = V' v
⊢ Holds D I V (pred_ X vs) ↔ Holds D I V' (pred_ X vs)
D : Type
I : Interpretation D
X : String
vs : List Var
V V' : VarAssignment D
h1 : ∀ v ∈ vs, V v = V' v
⊢ Holds D I V (pred_ X vs) ↔ Holds D I V' (pred_ X vs)