  On the other hand, Leibniz’s embrace of the principle of the equality of cause and effect helped inspire his development of a series of  ambitious positions that would collectively serve as the moorings of  his mature physics. The failure of Descartes’s conservation law  encouraged Leibniz to attach new significance to an alternative  conservation principle that he had learned from Huygens by 1669 at  the   latest.[9]  Leibniz came to see that if force is taken to be equivalent to the  quantity of vis viva – rather than the quantity of  motion as Descartes had implied – then, in cases such as those  highlighted by the Brief Demonstration, no violation of the  principle of equality of cause and effect need be tolerated. In  subsequent works, including his Dynamica de Potentia et Legibus  Naturae corporea (1689), Essay of Dynamics on the Laws of  Motion … (1690), and Specimen Dynamicum (1695), Leibniz attempts to build on this  discovery by suggesting further implications not only for the  conservation of force, but also for the laws of motion and even the  fundamental nature of physical bodies. One can see in his devastating critique of the Cartesian conservation law the seeds  of much of what is distinctive in his own mature physics.