case prop_2_ phi psi chi =>
  intro D I V E _
  simp only [Holds]
  tauto
Δ : List Formula
F phi psi chi : Formula
⊢ ∀ (D : Type) (I : Interpretation D) (V : VarAssignment D) (E : Env),
    (∀ H ∈ [], Holds D I V E H) → Holds D I V E ((phi.imp_ (psi.imp_ chi)).imp_ ((phi.imp_ psi).imp_ (phi.imp_ chi)))
no goals