 As discussed in previous sections, there are various ways in which Descartes’ laws of motion violate a strict relationism. One of the most problematic instances involves the relational compatibility of the fourth and fifth collision rules. Whereas the fourth rule concludes that a large object remains at rest during impact with a smaller moving body, such that the smaller body is deflected back along its initial path, the fifth rule concludes that a large body will move a smaller stationary object, “transferring to [the smaller body] as much of its motion as would permit the two to travel subsequently at the same speed” (Pr II 50). From a relational standpoint, however, rules four and five constitute the same type of collision, since they both involve the interaction of a small and large body with the same relative motion (or speed difference) between them. One might be tempted to appeal to the basic Cartesian tenet that motion and rest are different intrinsic states of bodies, or the reciprocity of transfer thesis, to circumvent this difficulty (see section 3): i.e., there is an ontological difference between a body that is, or is not, undergoing a translation with respect to its contiguous neighborhood, and this is sufficient to distinguish the case of rule four from rule five (since the large body is really at rest in four, and really in motion in five).