have : σ.fvarList.length = 0 := by simp
ξ : Type u_1
L : Language
h : IsEmpty ξ
inst✝ : DecidableEq ξ
σ : Formula L ξ
⊢ ∀* Rew.empty.hom σ = ∀' Rew.empty.hom σ
ξ : Type u_1
L : Language
h : IsEmpty ξ
inst✝ : DecidableEq ξ
σ : Formula L ξ
this : (Semiformula.fvarList σ).length = 0
⊢ ∀* Rew.empty.hom σ = ∀' Rew.empty.hom σ