apply IsAxiom.pred_3_
case a.a
F : Formula
v : VarName
Δ : Set Formula
h2 : ∀ H ∈ Δ, ¬isFreeIn v H
h1_phi : Formula
h1_1 : h1_phi ∈ Δ
⊢ IsAxiom (h1_phi.imp_ (forall_ v h1_phi))
case a.a.a
F : Formula
v : VarName
Δ : Set Formula
h2 : ∀ H ∈ Δ, ¬isFreeIn v H
h1_phi : Formula
h1_1 : h1_phi ∈ Δ
⊢ ¬isFreeIn v h1_phi