He was in another sense an anomalous mixture: a man apparently absorbed in mathematical and mystical theory, and yet possessed of practical ability and common sense. In 1687 he was chosen by the University of Cambridge to go with others and protest to James II the King’s attempt to have the University admit a Benedictine monk to a degree without taking the usual oaths impossible to a Catholic. The mission failed to dissuade the King, but the University must have approved Newton’s conduct of it, for he was chosen member for Cambridge in the Parliament of 1689. He served till the dissolution in 1690, and was re-elected in 1701, but he took no memorable part in politics.
His career was interrupted in 1692 by two years of physical and mental illness. He addressed to Pepys and Locke letters complaining of sleeplessness and melancholia, expressing fears of persecution, and mourning that he had lost “the former consistency of his mind.” 47 On September 16, 1693, he wrote to Locke:
Being of opinion that you endeavored to embroil me with women and by other means, I was so much affected that when one told me you were sickly and would not live, I answered, ‘twere better if you were dead. I desire you to forgive me for this uncharitableness. For I am now satisfied that what you have done is just, and I beg your pardon for having hard thoughts of you for it, and for representing that you struck at the root of morality in a principle you laid down in your book of ideas, and designed to pursue in another book, and that I took you for a Hobbist. I beg your pardon also for saying or thinking that there was a design to sell me an office, or to embroil me.
I am your most humble
and unfortunate servant,
Is. NEWTON 48
Pepys, in a letter of September 26, 1693, mentioned “a discomposure in . . . head or mind” evidenced by a message he had received from Newton. Huygens left at his death (1695) a manuscript in which he noted, under date of May 29, 1694, that “M. Colin, a Scotchman, informed me that eighteen months ago the illustrious geometer, Isaac Newton, had become insane,” but had “so far recovered his health that he began to understand the Principia.” Huygens sent the report to Leibniz in a letter of June 8, 1694: “The good Mr. Newton has had an attack of phrenitis which lasted eighteen months, and of which they say his friends have cured him by means of remedies and keeping him shut up.” 49 Some have supposed that this nervous breakdown led Newton from science to the Apocalypse, but we cannot say. It was said that “he never again concentrated after the old fashion, or did any fresh work”; 50 yet he solved almost at once, in 1696, a mathematical problem proposed by Johann Bernoulli “to the acutest mathematicians in the world”; and he did likewise with a problem set by Leibniz in 1716. 51 His answer to Bernoulli was sent anonymously through the Royal Society, but Bernoulli at once guessed the author to be Newton, recognizing, he said, “tanquam ex ungue leonem”—the lion from his toenail. In 1700 he discovered the theory of the sextant; he let it remain unknown except by a letter to Halley, and it had to be reinvented in 1730. And he seems to have filled creditably the difficult positions to which he was presently appointed by the state.
Locke, Pepys, and other friends had for some time negotiated to secure for Newton a governmental position that would get him away from the confinement of his room and laboratory at Cambridge. In 1695 they persuaded Lord Halifax to offer him the post of warden of the Mint. The appointment was no sinecure, and no act of charity; the government wished to use Newton’s knowledge of chemistry and metallurgy in minting a new coinage. In 1695 he moved to London, where he lived with his niece Catherine Barton, the mistress of Halifax. 52 Voltaire felt that the charm of this niece led Halifax, as chancellor of the exchequer, to make Newton master of the Mint in 1699; 53 but this bit of gossip hardly explains why Newton continued to hold that office through his remaining twenty-eight years, and to the general satisfaction.
His old age should have been happy. He was honored as the greatest of living scientists; not till our own time did any man of science enjoy such wide acclaim. He was elected president of the Royal Society in 1703, and annually thereafter till his death. In 1705 he was knighted by Queen Anne. When he rode in his carriage through the London streets people gazed with awe upon his pink face, majestic and benevolent under a mass of white hair; and they could not always see that he had expanded out of proportion to his modest height. He enjoyed a good salary, £ 1,200 a year, and invested his savings so wisely that he left £ 32,000 when he died, 54 though he had been generous in gifts and charity. He surmounted successfully the South Sea Company fiasco. However, he was moody, sometimes irritable, suspicious, secretive, always timid but proud. 55 He loved privacy, and did not make friends readily. In 1700 he proposed to a rich widow; nothing came of it, and he never married. Highstrung and morbidly sensitive, he bore criticism painfully, resented it sharply, and fought back stoutly in controversy. He was conscious of his own work and ability, but he lived modestly until his salary and his savings enabled him to have six servants and enjoy a high place in London society.
In his seventy-ninth year he began to repay his debt to nature. Diseases that respect no genius afflicted him—stone in the bladder and urinary incontinence; at the age of eighty-three he suffered from gout, and at eighty-four from hemorrhoids. On March 19, 1727, the pains from the stone were so severe that he lost consciousness. He never regained it, but died the next day, in his eighty-fifth year. He was buried in Westminster Abbey after a funeral led by statesmen, nobles, and philosophers, in a pall borne by dukes and earls. Poets swathed him in elegies, and Pope composed a famous epitaph:
Nature and Nature’s laws lay hid in night;
God said, Let Newton be! and all was light.
Voltaire even in old age was moved when he told how, in his English exile, he had seen a mathematician buried with the honors of a king. 56
Newton’s fame grew to almost absurd heights. Leibniz judged his rival’s contributions to mathematics to be equal in value to all previous work in that science. 57 Hume considered Newton “the greatest and rarest genius that ever rose for the adornment and instruction of the species,” 58 and Voltaire modestly agreed. 59 Lagrange called the Principia “the greatest production of the human mind,” and Laplace assured it for all time “a pre-eminence above all other productions of the human intellect”; Newton, he added, was the most fortunate of men, for there is only one universe, and one ultimate principle in it, and Newton discovered that principle. 60 Such judgments are precarious, for “truth,” even in science, wilts like a flower.
If we rank the greatness of a man by the least subjective test, the spread and duration of his influence, Newton can be compared only with the founders of world religions and pivotal philosophies. For a time his influence upon English mathematics was harmful, for his “fluxions” and their notation proved less convenient than the calculus and notation with which Leibniz prevailed on the Continent. For a century his corpuscular theory of light seems to have impeded the progress of optics, though some students now find much help in Newton’s view. 61 In mechanics his work has proved endlessly creative. “All that has been accomplished in mechanics since his day,” wrote Ernst Mach, “has been a deductive, formal, and mathematical development . . . on the basis of Newton’s laws.”62
Theologians at first feared the influence of the Principia on religion; but Bentley’s Boyle lectures (1692), encouraged by Newton, turned the new world-view to the support of faith by stressing the apparent unity, order, and grandeur of the universe as evidences of the wisdom, power, and majesty of God. However, the same Newtonian system was accepted by the deists as strengthening their replacement of the Christian theology with a simple acceptance of one God, or even their identification of God with Nature and her laws. Probably the final influence of Newton on religion was injurious; despite his protests, and his million words of theological writings, freethinkers supposed that he had conceived a self-subsistent world, and had brought deity into it as a comforting afterthought. In France especially, Newton’s cosmology, though presented deistically by Voltaire, encouraged the mechanistic atheism of many philosophes.
Between the decline of the Cartesian cosmogony in France (c. 1740) and the rise of relativity theories and quantum mechanics in the twentieth century, Newton’s “System of the World” met no serious challenge, and seemed to be verified by every advance or discovery in physics or astronomy. So far as an outsider can understand such arcana, the principal dissents of contemporary physicists from Newton’s mechanics are:
1. Newton took space and distance, time and motion, as absolute—i.e., not varying in quantity according to anything outside themselves. 63 Einstein considered them relative—varying with the position and motion of the observer in space and time.
2. Newton’s first law of motion apparently assumed that a body might “continue in a state of rest, or of uniform motion in a straight line.” But “rest” is always relative, like the rest of a traveler in a speeding plane; all things move, and never in a straight line, for every line of motion or action is deflected by surrounding bodies (as Newton realized).
3. Newton thought of mass as a constant; some contemporary physicists think of it as varying with the relative velocity of observer and object.
4. “Force” is now looked upon as a convenient but not necessary concept in science, which aims to content itself with describing sequences, relations, and results. We do not and need not (we are told) know what “it” is that passes from a moving object to an object that it strikes; we need only record the sequences, and assume (never with absolute certainty) that these will be in the future what they have appeared to be in the past. Gravitation, in this view, is not a force but a system of relationships among events in space and time.
It is a consolation to learn that these and other emendations of Newton’s mechanics are of importance only in fields (such as electromagnetic phenomena) where particles seem to move with a speed approaching the velocity of light; elsewhere the divergence between the old physics and the new may be safely ignored. Philosophers, cured of certainty by history, may still retain a humble skepticism about contemporary ideas, including their own; they will sense a fluent relativity in relativity formulas; and they will remind all delvers in atoms and stars of Newton’s own final estimate of his epochal achievement:
I do not know what I may appear to the world; but to myself I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, while the great ocean of truth lay all undiscovered before me. 64