  In a short piece fully and tellingly entitled A Brief  Demonstration of a Notable Error of Descartes and Others Concerning a Natural Law, According to which God is Said Always to Conserve the  Same Quantity of Motion; a Law which They also Misuse in  Mechanics, Leibniz publicly attacked Descartes’s conservation  principle and thereby the foundations of Cartesian physics (GM  VI.117–119/L 296–302). The central argument of the Brief  Demonstration is ingenious and elegant, but only deceptively  straightforward, and Leibniz continued to develop and expand upon its central theme for many years after its initial public presentation in  1686.[15] 