This chapter introduces Newton’s intellectual biography before the publication of the Principia, and provides a new account of his methods as a natural philosopher. From the 1660s onwards, Newton – in line with his mentor Isaac Barrow and with other mixed mathematicians discussed in I.1 – sought a phenomenological science of properties, actively disdaining conjecture concerning the underlying causes of phenomena. The famous ‘De gravitatione’ manuscript is shown to stem from hydrostatical lectures delivered in 1671; contrary to most of the literature, it contains no elaborate metaphysics of divine omnipresence. Newton’s interest in revealed theology developed when he had to perform disputations in 1677; he did not become an antitrinitarian until the late-1680s, and there is no evidence that his theological views influenced the Principia. For all its mathematical sophistication, that work was very much the product of a methodology not much different from that which mixed mathematicians had been advocating for the previous century. In particular, Newton’s ideas at this time bear a strong conceptual resemblance to those developed by other English mixed mathematicians, such as John Wallis. The very first ‘Newtonians’ recognised the anti-metaphysical thrust of his ideas.