We have known since Galileo and Newton, that the motion of a body involves an inherent struggle between inertia and force. According to the old view, the inertial tendency of persistence, the “guidance”, which gives a body its natural inertial motion, is based on a formal geometric structure of the spacetime (uniform motion in a straight line) which resides once and for all in spacetime independently of any natural processes. This assumption Einstein rejects; because whatever exerts as powe