  On the one hand, the argument of the Brief Demonstration forced Leibniz to rethink the foundations of his early theory of motion. For the charge of violating the principle of the equality of cause and effect that he leveled against Cartesians spoke as well against the laws of the TMA and the HPN. The paradoxical result of the ideal laws of the TMA – that a tiny body moving with a given speed might impart the same speed to a relatively enormous body – appeared, at least intuitively, as an example of a potentially even greater increase in local force than anything allowed by Descartes’s rules of impact. Conversely, according to the phenomenal laws of the HPN, since the combination by impact of two conatuses can fall short, but never exceed, the strict sum of the conatuses of the two individual bodies, the total conatus present in the world must naturally decline over time – another violation of the equality principle. In short, in the argument of the Brief Demonstration, Leibniz found a devastating criticism not only of Cartesian physics, but also of Early Leibnizian physics. 