This chapter explains what Isaac Newton means with the phrase “absolute, true, and mathematical time” in order to discuss some of the philosophic issues that it gives rise to. It describes Newton's thought in light of a number of scientific, technological, and metaphysical issues that arose in seventeenth‐century natural philosophy. The first section discusses some of the relevant context from the history of Galilean, mathematical natural philosophy, especially as exhibited by the work of Christiaan Huygens. The second section offers a (...) close reading of what Newton says about time in the Principia's Scholium to the definitions. It argues that Newton allows us to conceptually distinguish between “true” and “absolute” time from the vantage point of Newton's dynamics. The third section, in the context of a brief account of Descartes' views on time, discusses the material that Newton added to the second edition of the Principia in the General Scholium. (shrink)