 Consider first Leibniz’s mechanics. Since his laws are what is now (ironically) often called ‘Newtonian’ elastic collision theory, it seems that they satisfy both of his requirements. The laws include conservation of kinetic energy (which we identify with virtus), but they hold in all inertial frames, so the kinetic energy of any arbitrary body can be set to any initial value. But they do not permit the kinetic energy of a body to take on any values throughout a process. The laws are only Galilean relativistic, and so are not true in every frame. Furthermore, according to the laws of collision, in an inertial frame, if a body does not collide then its Leibnizian force is conserved while if (except in special cases) it does collide then its force changes. According to Leibniz’s laws one cannot determine initial kinetic energies, but one certainly can tell when they change. At the very least, there are quantities of motion implicit in Leibniz’s mechanics – change in force and true speed – that are not merely relative; the folk reading is committed to Leibniz simply missing this obvious fact.