{L : FirstOrder.Language} →
  {α : Type u'} →
    {motive : (a : ℕ) → L.BoundedFormula α a → Sort u_1} →
      {a : ℕ} →
        (t : L.BoundedFormula α a) →
          t.ctorIdx = 0 → ({n : ℕ} → motive n FirstOrder.Language.BoundedFormula.falsum) → motive a t