 Like many philosophers who worked in the wake of Galileo and of Descartes, it seems that Newton never extensively analyzed Aristotelian ideas about nature. He would have encountered such ideas in the curriculum at Trinity College, but there is not much evidence that he took them seriously. Instead, he focused on the “modern” thinkers that enterprising young students were told to read outside of the standard  curriculum.[10]  And in England in Newton’s day, the greatest modern philosopher of nature was thought to be Descartes (Heilbron 1982: 30). There is substantial evidence that Newton took Descartes’s ideas very seriously, and expended considerable energy thinking them through and eventually coming to criticize them. Some of that evidence comes from a manuscript that was first transcribed and published in 1962 by the great historians of science, Marie Boas Hall and A. Rupert Hall. The untitled manuscript, now known as “De Gravitatione” after its first line, has been the subject of extensive discussions over the past fifty years because it indicates the depth of Newton’s interest in Cartesian ideas in metaphysics and natural philosophy. Despite its importance to contemporary understandings of Newton’s relation to Cartesianism, and much else besides, De Gravitatione is not without its problems. First and foremost, the manuscript lacks a date, and there is no scholarly consensus regarding its precise  provenance.[11]  Second, the manuscript was never finished, so it is difficult to assess its relationship with Newton’s mature thinking in philosophy. Finally, the manuscript was not published during Newton’s lifetime, so there are questions about whether it represents his considered views. Despite these facts, the text contains a treasure trove of arguments concerning Cartesian ideas. For instance, it dispels the easily formed impression that Newton sought, in the Principia, to undermine a Leibnizian conception of space and time, as his defender, Samuel Clarke, would attempt to do years later in the correspondence of 1715–16 (discussed below). Although Leibniz did eventually express what became the canonical early modern formulation of “relationalism” concerning space and time—the view, roughly, that space is nothing but the order of relations among physical objects, and time nothing over and above the succession of events involving those objects—and although Newton and Clarke were highly skeptical of such a view, it is misleading to read the Principia through the lens provided by the later controversy with the Leibnizians. Newton’s extensive attempt in De Gravitatione to refute Descartes’s conception of space and time in particular indicates that the Scholium should be read as providing a replacement for the Cartesian  conception.[12]  That is, Newton had a Cartesian, and not a Leibnizian, opponent primarily in mind when he wrote his famous articulation of “absolutism” concerning space and time. Unlike questions about Newton’s methods and his apparent deviation from the norms established by mechanist philosophers like Descartes and Boyle, Newton’s conception of space and time, along with his view of the divine being, did not immediately engender a philosophical debate. It was Leibniz more than any other philosopher who eventually succeeded in fomenting a philosophical debate in which the “Newtonian” conception of space, time and the divine would play a central role (see below). But Leibniz’s philosophical views were relatively unknown when Newton first formed his conception--to the young Newton writing the Principia, Leibniz was another mathematician and not yet a contributor to natural philosophy. Instead, it was Descartes’s view of space, the world, and God, which he pondered in his youth and eventually came to reject.