Leibniz rejected the Cartesian formulation. When examining rising and falling bodies, he recognized that their behavior reveals a different quantity, derived from Galileo’s law of fall, which is the product of mass and velocity squared (mv²). Leibniz thought this implied Descartes’s quantity to be false and that only mv², not mv, is conserved. Leibniz called this new quantity “living force” (vis viva); we call it kinetic energy now. Force is real, he argued, and it is more than a quantity (mv of Decartes)— it is the basic quality of nature and its activity can be observed in nature. Leibniz expanded physics to a dynamics.