Newton was born early in the 1640s, one of the most turbulent decades in English history, a time when the bloody civil war fought between King Charles I and the English Parliament ravaged the nation. The conflict was eventually won by the Parliamentary forces, led by the great general Oliver Cromwell, and in 1649 they made the shocking decision to execute Charles and do away with the monarchy entirely. Cromwell, who took the title Lord Protector, ruled the island nation as a military dictator for the next decade, and the zealous Puritans, the strict Protestants who had provided Parliament's chief source of support in the civil war, dominated Cromwell's government. The Puritans, as their name suggests, originally desired to purify the Church of England, or Anglican Church. However, once in political power they fell victim to excessive ambition: seeing vice and vanity everywhere, they went about imposing their austere code on the entire country. Thus Cromwell's government soon banned all non-Puritan forms of Christianity, closed down all theaters and other entertainment venues, frowned upon all music (save for hymns), halted commerce on Sundays, and administered harsh penalties for all crimes. England was purified with a vengeance.

The Puritan dictatorship lasted until 1660, when Cromwell died, ushering in a brief period of disorder. Parliament brought this chaos to an end by inviting Charles I's exiled son back to sit upon his father's throne. On May 25, 1660, he landed in England and was crowned as Charles II. He and his new administration disestablished Puritanism and returned the Anglican Church to its more moderate form: the period known as the Restoration began. But the religious and political tensions continued, and would soon manifest themselves in further struggle. Charles II reigned until 1685, and was succeeded by his brother, James II, a Roman Catholic. Since the Protestant Reformation, Catholics had been an oppressed minority in England, and when James began to restore their rights, the Protestant nobility and Parliament feared that he planned to impose Catholicism upon the nation. In 1688, the year after Newton published his Principia, James was toppled in a bloodless revolt known as the Glorious Revolution. The English nobles invited a new ruler to come to Britain: they offered the throne to William of Orange, a committed Dutch Protestant married to James's daughter Mary; he crossed the English Channel at the head of an army--though no fighting became necessary--and was acclaimed as King William III, while the luckless James fled to France. Protestantism, and the Anglican Church, had secured its power.

Newton played no direct role in any of these upheavals, but they impacted his career nonetheless. He was a committed Protestant, who always supported the Anglican Church and demonstrated an animosity toward Catholicism; these views allowed him to gain much status after the triumph of William and Mary, as he received royal favor and eventually a royal appointment at the mint. But his era influenced not only the course of his life, but the course of his thinking: for it was during the Puritan age that Newton formed his personal religious philosophy, and a Puritan sensibility--with its emphasis on the inerrancy of scripture, the role of the Bible as the sole source of religious truth, and the imminence of the apocalypse--infused all of his theological writings.

Although Newton did not play an active role in any religious or political revolutions, he did play a crucial role in a revolution in thought: the Scientific Revolution. The great minds of the 16th and early 17th centuries opened new vistas, breaking away from the traditional medieval view of man and the cosmos and making remarkable discoveries. Nicholas Copernicus, Tycho Brahe, Johannes Kepler, and Galileo Galilei had changed the face of astronomy and physics, while William Harvey and Andreas Vesalius had begun the mapping of the human body. In Newton's own time, Englishmen like his rival Robert Hooke, the astronomer Edmund Halley, and the great chemist Robert Boyle were further contributing to the expansion of scientific knowledge. On the European continent, Gottfried von Leibniz revolutionized mathematics, while the Danish astronomer Christian Huygens explored the heavens, and a Frenchman, René Descartes, created a system of physics in which the universe was filled with tiny particles, whose motion and interaction drove the moon and planets. But Descartes--indeed, all of Newton's scientific contemporaries--would eventually take a back seat to Newton, whose Principia, which uncovered the fundamental law of the universe, can be considered the greatest achievement in an age of scientific triumphs.