 We see from this period that Galileo’s law of free fall arises out of this struggle to find the proper categories for his new science of matter and motion. Galileo accepted, probably as early as the 1594 draft of Le Meccaniche, that natural motions might be accelerated. Particularly in the cases of the pendulum, the inclined plane, free fall, and projectile motion, Galileo must have observed that the speeds of bodies increase as they move downwards and, perhaps, do so naturally. But that accelerated motion is properly measured against time is an idea he realized only later, chiefly through his failure to find any satisfactory dependence on place and specific gravity. Also at this time, he began to think about percussive force. For many years, he thought that the correct science of these phenomena should describe how bodies change according to where they are on their paths. Specifically, it seemed that height is crucial. Percussive force is directly related to height and the motion of the pendulum seems to involve equilibrium with respect to the height of the bob (and time also, but isochrony did not lead directly to a recognition of time’s importance).