  In his Essay on Dynamics, Leibniz shows how from any two of  his conservation laws the third law may be derived. This might  suggest that Leibniz sees all three as being on a par with one  another. In fact, however, he insists that the conservation of  vis viva is more fundamental than the conservation  of relative velocity or common progress. His reasons for privileging  mv2 in this way are far from clear, but he must  have recognized them to be necessarily metaphysical. Although the  measurement of mv2 is relative to a choice of  reference frame, Leibniz probably thought that it had a better claim  to tracking an intrinsic property of bodies in light of the  considerations he raises in his Brief Demonstration. For  Leibniz, vis viva is a force attributable to particular  bodies in virtue of which they are able to perform work on other  bodies – or as in the case of a pendulum – on themselves; he  thus held the conservation of vis viva to be the most  fundamental, overarching conservation law for the physical world. 