∀ {α : Type u} {r : α → α → Prop} {motive : (as bs : List α) → List.Lex r as bs → Prop},
  (∀ {a : α} {l : List α}, motive [] (a :: l) ⋯) →
    (∀ {a₁ : α} {l₁ : List α} {a₂ : α} {l₂ : List α} (h : r a₁ a₂), motive (a₁ :: l₁) (a₂ :: l₂) ⋯) →
      (∀ {a : α} {l₁ l₂ : List α} (h : List.Lex r l₁ l₂), motive l₁ l₂ h → motive (a :: l₁) (a :: l₂) ⋯) →
        ∀ {as bs : List α} (t : List.Lex r as bs), motive as bs t