  Unlike the quantity of progress, but like relative velocity, the  quantity of vis viva appears to be conserved only  in elastic collisions. At the macro-level, when a lump of soft clay  strikes another lump of soft clay, their momentum is conserved but  kinetic energy is lost. As noted above, rather than abandon the  universality of his third law, Leibniz suggests instead that energy  is conserved but redistributed to the minute parts of which the clay  is composed. In this way, he tells us “that which is absorbed  by the minute parts is not absolutely lost for the universe, although it is lost for the total force of the concurrent bodies” (GM  VI.231/Langley 670). 