  Continuing to restrict ourselves to kinematics, Leibniz appears to  embrace something even stronger than Galilean invariance. He suggests that not only is constant linear motion observationally  underdetermined, but furthermore that “If we consider change in position alone, or that which is merely mathematical in  motion,” then all motion is observationally  underdetermined (A VI.iv.2017/Lodge 2003, 278). That is to say, he  seems to accept that not even accelerations – changes in  direction or speed – can be detected by empirical observation.  Thus, for example, he writes: