{X Y S : AlgebraicGeometry.Scheme} →
  {f : X ⟶ S} →
    {g : Y ⟶ S} →
      {motive : AlgebraicGeometry.Scheme.Pullback.Triplet f g → Sort u_1} →
        (t : AlgebraicGeometry.Scheme.Pullback.Triplet f g) →
          ((x : ↥X) →
              (y : ↥Y) →
                (s : ↥S) → (hx : f x = s) → (hy : g y = s) → motive { x := x, y := y, s := s, hx := hx, hy := hy }) →
            motive t