In 1696, fully recovered from his nervous breakdown, or "Black Year," Newton finally achieved the governmental position he had so ardently desired, as he was named warden of the Mint (the agency responsible for coining money in England). He moved to London now, and lived with his niece, Catherine Barton, who was the mistress of Lord Halifax, a high-ranking government official. In 1699, Halifax promoted Newton from warden to master of the Mint, a position that the scientist would hold for the remaining twenty-eight years of his life. While his promotion may have been due, in part, to his niece's influence on Halifax, Newton's chemical and metallurgical knowledge must have proved useful in the minting of new coinage--and his tenure as master of the Mint had been reasonably successful by all accounts.

Meanwhile, with Hooke's death, Newton was finally (1703) elected to the presidency of the Royal Society. His period of discovery, in a sense, had given way to a period of political power, as he became, in one contemporary's term, the "Perpetual Dictator" of the Society. The early decades of the 18th century saw the Newtonian worldview sweep England, and Newton himself enjoyed wider acclaim than any scientist before or since. Queen Anne, daughter of William and Mary, knighted him in 1705, thus granting him the aristocratic rank he had always desired. Foreign visitors crowded in to see him, artists jostled to paint his portrait, and crowds gathered to watch his carriage roll through the streets of London. This ever-increasing fame resulted partially from the gradual acceptance of the brilliance of Principia; but Newton himself also actively managed and embellished his image. He dealt with his rivals briskly: when John Flamsteed, the stiff-necked Royal Astronomer, questioned Newton's authority and tried to undermine him, Newton made sure that Flamsteed's position was reduced and his writings censored. With Hooke's death, most of the older generation of English scientists had passed away, and the Society soon consisted of Newton's friends (men like Halley) and his young disciples, who were encouraged to dedicate their work to the "divine Newton" and generally compete for his favor. Previously a loose confederation of intellectuals, the Society was brought to heel and became a tightly disciplined organization, blessed with a sound financial situation and governed by the "autocrat of science," England's great genius, Isaac Newton.

Meanwhile, Newton's ambition and fierce attachment to his own discoveries continued to lead to conflict with other scientists. Newton did not understand the concept of sharing credit for discoveries; the notion of science as a cooperative venture was completely foreign to him. After Hooke's death, Newton was quick to acquire a new rival: his antagonist was now Leibniz, the brilliant German mathematician, who still stands with Newton as one of the great geniuses of the age.

In 1704, Newton finally published the results of his early work on light, in a volume entitled Opticks. In an appendix to this book Newton discussed his work, dating from the 1660s, with calculus, or "fluxions," as he termed it. Yet the discussion was not as groundbreaking as Newton would have liked: Leibniz had also developed a system of calculus in the 1670s, one that differed from Newton's own. Indeed, the two men had known of each other's pursuits, and had amiably exchanged letters; in the Principia Newton had acknowledged that Leibniz had developed, independently, a "method of the same kind . . . which hardly differed from mine." But in the early 1700s, a rivalry developed over whose discovery had come first. A friend of Newton, writing in 1699, hinted that Leibniz had stolen his calculus from Newton's fluxions. In response, Leibniz penned an anonymous review of the Opticks in 1705, in which he all but accused Newton of plagiarizing his research. Newton's acolytes fired back furiously, and in 1712 the Royal Society solemnly appointed a committee to investigate the matter. But Newton controlled the Royal Society: he appointed the committee and oversaw its research; and so their conclusion, unsurprisingly, asserted his priority in discovery. Leibniz, lacking the apparatus of a Society to press his case, could do nothing but continue to denigrate Newton's achievements privately, in letters to friends. The third edition of the Principia, published in 1706, now contained no references to the German rival. (It is worth noting, however, that more objective scholars have corroborated the Society's findings: Newton's work seems to have preceded Leibniz's by almost a decade.) In England, at least, Newton had achieved victory, and mathematicians adopted his method of notation, rather than that Leibniz had proposed. But in the long run, the German mathematician's system of calculus proved more convenient, and on the European continent it prevailed over the "fluxions"--a triumph that Leibniz would have doubtless appreciated, after seeing himself out-politicked, like others before him, by the relentless Newton.