 The eighteenth-century tendency to discuss Newton’s philosophy, rather than his science, may have an odd ring to modern ears. In this case, however, the evolution of the English language tracks a substantive intellectual development. As a matter of historical fact, the category of the scientist—along with that word in English—is a nineteenth-century invention. Specifically, at a meeting of the British Association for the Advancement of Science in June of 1833, the Cambridge philosopher William Whewell coined the word “scientist”. Whewell said that just as the practitioners of art are called “artists”, the practitioners of science ought to be called “scientists”, indicating that they should no longer be called  philosophers.[1]  Indeed, before the early nineteenth century, people like Newton were called “philosophers”, or more specifically, “natural philosophers”. During the seventeenth century, and well into the eighteenth (at least until 1750, if not later), figures like Newton worked within the century’s old tradition of natural  philosophy.[2]  The modern disciplines of physics, chemistry, biology and so on, had not yet been formed. (The words ‘physics’ in English, ’physique’ in French, and ‘physica’ in Latin were often used, but had a very broad meaning, like “natural philosophy.”) Philosophers who studied nature investigated such things as planetary motions, the nature of matter, and the possibility of a vacuum, but they also discussed many aspects of human beings, including the psyche, and how nature reflects its divine creator (Hatfield 1996). As the title of Newton’s magnum opus, Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), suggests, he intended his work to be in dialogue with Descartes’s Principia Philosophiae (Principles of Philosophy, 1644). Descartes’s Principles is a complex text that includes discussions of everything from the laws of nature to the nature of God’s causal influence on the world. Descartes had famously promised that his physics required nothing more than the principles of geometry and pure mathematics (Principles, Part Two, §64). Although Descartes was a great mathematician, the author of a major work in geometry in 1637, Newton thought nonetheless that he had not lived up to this promise, so he would assuredly introduce mathematical principles for natural philosophy. Just as Descartes had sought to replace Aristotelian or “Scholastic” methods and doctrines in natural philosophy, Newton sought to replace Descartes’s. It is therefore more historically accurate and more illuminating to interpret Newton within the historical stream of natural  philosophy.[3]