The Relativity of the Newtonian Dynamics.

It is a commonplace observation in respect of Newtonian dynamics that although the fundamental laws assume at the outset an absolute frame of reference, yet they are not sufficient to determine uniquely what that frame of reference must be; or in other words, although to every moving point a velocity is assigned, yet the laws of dynamics as stated by Newton are not sufficient to determine a velocity which, more than any other arbitrary velocity, can be said to be the velocity of any particular point. Put more definitely, it is known that if any set of axes in space can be specified relative to which the laws of dynamics are satisfied by a system of bodies, then any other set of axes which moves continually with a constant velocity of translation and with no rotation relatively to the former set, is also a valid framework for the dynamics of the same system of bodies.

It is important to distinguish this dynamical relativity from any philosophic dogma as to the a priori impossibility of the mind conceiving of an absolute position or motion in space. For such a proposition would be of much wider content than that stated above.