∀ {R : Type u_1} {V : Type u_2} {P : Type u_4} [inst : Ring R] [inst_1 : PartialOrder R] [inst_2 : AddCommGroup V]
  [inst_3 : Module R V] [inst_4 : AddTorsor V P] [IsOrderedRing R] [IsDomain R] [Module.IsTorsionFree R V] {x y z : P},
  Wbtw R x y z → (Wbtw R z x y ↔ x = y)