Probably not too many physicists and philosophers of science would disagree with Wolfgang Rindler's judgement that with the development of SR Einstein took the step that would "destroy the classical concept of time."¹ But what is or was the classical concept of time, and how did Einstein's critique render it untenable? In order to answer those questions, we need to recur to the fountainhead of the classical concept of time: Isaac Newton and his Philosophiae naturalis principia mathematica.