  From the observational under-determination of all motion considered  kinematically, Leibniz infers that if there were nothing more to  motion than change of position relative to other bodies, then there  would be no real or genuine motion in the world at   all.[29]  He is thus committed to maintaining that if there were nothing more  to motion than relative change of position, then, since motion could  be ascribed with equal right to, say, Train A or Train  B, then there would be no fact of the matter as to whether  Train A or Train B is moving, and thus it would  make no sense to say that either Train A or Train B is moving. The suggestion that motion be treated as irreducibly  relational – so that motion could be ascribed to Train  A relative to one reference frame, and to Train B  relative to another reference frame – would have had no  attraction for Leibniz, who consistently denied that there are any  genuine external relations (i.e. relations that do not wholly  supervene on intrinsic properties). 