∀ {T : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} T] {X : T} {U V : CategoryTheory.Under X} {g : U ⟶ V}
  (motive : (f : U ⟶ V) → f.right = g.right → Prop) (f : U ⟶ V) (h : f.right = g.right),
  (∀ (left : U.left ⟶ V.left) (b : U.right ⟶ V.right)
      (w :
        CategoryTheory.CategoryStruct.comp ((CategoryTheory.Functor.fromPUnit X).map left) V.hom =
          CategoryTheory.CategoryStruct.comp U.hom ((CategoryTheory.Functor.id T).map b))
      (h : { left := left, right := b, w := w }.right = g.right), motive { left := left, right := b, w := w } h) →
    motive f h