This great man, conceiving very distinctly that matter cannot move itself and that the natural motor force of all bodies is none other than the general will of the Author of nature, and that hence the communication of the motion of bodies at their collision can come only from this same will, let himself believe that we could provide the rules of the various communication of motions only through the proportion found between the different sizes of the bodies struck, since it is not possible to penetrate the designs and will of God.