Let there be Newton

December 24, 1999

While some pundits doubt whether the 17th-century revolution in science took place, advances in knowledge were undeniably made. Robert Fox surveys an epoch of change, from Galileo's vision of a heliocentric universe to Newton's law of gravitation and his immortalisation by the poet Alexander Pope.

or the historian Herbert Butterfield, writing half a century ago, the scientific revolution of the 17th century outshone "everything since the rise of Christianity"; by comparison the Renaissance and the Reformation were "mere episodes". Since Butterfield wrote, scholarly opinion has undergone a seachange. We now recognise a greater degree of continuity between the new departures in science that Butterfield regarded as so important, and older, Aristotelian or magical ways of thinking about the natural world. In this rethinking, the very term "revolution" has taken a battering. Steven Shapin's recent assertion that "there was no such thing as the scientific revolution" expresses a scepticism that has become widespread. But, equally, the book in which Shapin made this deliberately paradoxical assertion did nothing to undermine the events that the term "scientific revolution" conventionally evokes.

Whatever balance we strike between continuity and discontinuity with the past, it is beyond question that the sum of knowledge about the natural world increased at an unprecedented rate between 1600 and 1700 and that methods for acquiring and ordering that knowledge were transformed. Discussions of method, in fact, were at the heart of what occurred. In this, Francis Bacon's work was exemplary. By the early years of the 17th century, Bacon had articulated not only an excoriating dismissal of what he saw as the authoritarian, book-bound learning of the scholastic tradition but also a new method whose combination of sense experience and inductive reasoning would lay bare the truths about nature, truths that could then be wielded in pursuit of his ideal of material improvement.

Bacon's time as an influential figure came only after his death in 1626. But even during his lifetime dissatisfaction with traditional practices for the acquisition and marshalling of natural knowledge was gathering pace across Europe. In Italy, Galileo's conflict with the Catholic church was already set on the disastrous course that had begun with his observations with the first telescope in 1609. Galileo's observations raised profound difficulties for Aristotelian cosmology, and he spared his opponents in the church no discomfiture in what quickly became open warfare.

Works of an earlier age, inspired by J. W. Draper's History of the Conflict between Religion and Science (1875) and A. D. White's A History of the Warfare of Science with Theology in Christendom (1895), commonly saw the confrontation as a mark of the enduring incompatibility of scientific and religious modes of thought. But more recent studies make this "conflict" thesis hard to sustain. They reveal Galileo as arrogant and unready for the compromise that a number of enlightened scholars urged upon him. As those scholars saw clearly, the fact that the geocentric Aristotelian universe, with its clear distinction between the region of change and decay below the sphere of the moon and that of enduring perfection beyond it, was in tatters did not imply that Copernicus's heliocentric alternative had to be adopted. But the way of informed but closed debate within the confines of the church was never Galileo's way, and his insistence that the church should publicly accept or deny the truth of the Copernican system led inexorably to his trial and enforced recantation before the Holy Office in 1633.

Galileo's fate, compounded by the years of house arrest until his death in 1642, ensured his enthronement as the martyr of science. More immediately, it helped to accelerate acceptance of his views, with ramifications beyond technical astronomy into the realm of perceptions of the human race's position in the universe.

In the geocentric universe, human beings occupied the most degraded place in creation, a central region of change and corruption appropriate to their fallen state. With that sense of humiliation, however, went a sense that, for good or ill, they mattered. Heliocentricity in itself did not wholly undermine such a belief, but as the idea that our solar system might be just one of an unimaginable number of such systems caught hold, the sense of being a mere speck in a possibly infinite universe disturbed many. Some found consolation in wonder at a God who cared for us despite our insignificance. Others fell prey to the profound disquiet of the French philosopher Blaise Pascal before the "eternal silence" of infinite space and the collapse of what Alexandre Koyre has analysed as the "closed world" of the Middle Ages and Renaissance.

A universe devoid of moral significance, in which human destiny appeared to count for so little, lent itself easily to the new mechanical metaphor for the workings of nature that established itself about the middle of the century. Foremost among the early conceptions of the world as a machine were those of Pierre Gassendi and Rene Descartes, writing in the 1630s and 1640s.

Gassendi drew eclectically on the past, particularly the ancient doctrines of Epicurus and Lucretius, who saw matter as composed of indivisible atoms moving about in a void. For Descartes, everything was made up of three types of matter, distinguished from one another by the fineness of their constituent particles. The motion of these particles and the impacts between them accounted for all the processes of the physical world. Magnetism, on the Cartesian model, was explained by the emanation from a magnet of screw-threaded particles, invisible but conceived by analogy with bullets from a gun; the human body became an assemblage of pulleys and levers in which the finest matter - the body's "animal spirits" - yielded the phenomena of life; and the heavens were depicted as a plenum filled with whirlpools of Cartesian matter that carried the stars and planets in their courses like twigs on the surface of water.

The significance of Gassendi and Descartes as mechanical philosophers lay far less in the particular doctrines they advanced than in their belief that mechanisms of some kind lay behind all the workings of nature. In the mainstream of natural philosophy in the mid- and later 17th century the belief assumed the status of a dominant (though not exclusive) orthodoxy. Agreement on the way in which the size, shape and motion of atoms or other particles engendered observable phenomena was elusive, but the prevailing optimism of the age, allied to remarkable advances in experimental technique in the mid-century, sustained an expectation that it was only a matter of time before certainty would be achieved. In this expectation, the transformation of the microscope from the simple magnifying lens that it had been earlier in the century to the form it had assumed by 1660, with its draw tubes, eye lens, field lens and biconvex objective lens, played a prominent role. Its refinement laid bare a new realm of nature, fostering hopes that the structure of matter might one day become accessible.

Not everyone, it must be said, shared these hopes. But few were immune to the general excitement that advances in instrumentation aroused. Who could remain unmoved by the plates of Robert Hooke's Micrographia (1664)? The intricacy of the body of a flea, the exquisitely structured eye of a fly and the details of a butterfly's wing all left readers marvelling at the beneficence of God, the master craftsman.

By the last quarter of the 17th century, the "book of nature" (to invoke a metaphor favoured by Galileo) was being read with unprecedented acuity. Improved instruments had extended the power of the senses; new ones (the thermometer and the barometer, for example) opened new realms of inquiry; and, in natural history, the lands in America, Africa and Asia, whose exploration had proceeded apace since the 16th century, were providing ever more subjects for study. No less important were new social settings for the pursuit and exchange of natural knowledge, notably the scientific societies and academies of which the Royal Society in London and the Academie Royale des Sciences in Paris, both founded in the 1660s, were particularly eminent examples. Here, in settings whose formality and permanence set them apart from the more ephemeral societies and circles of the Renaissance and the early 17th century, members observed and evaluated the work of their peers and, no less importantly, gained entry to a wider Republic of Letters that a rising tide of international correspondence (such as that of the first secretary of the Royal Society, Henry Oldenberg) and learned journals (such as the Royal Society's Philosophical Transactions) helped to define.

It is a mark of the success and visibility of the new methods and models that they were always the butt of satire. In Thomas Shadwell's The Virtuoso (1676), Sir Nicholas Gimcrack was portrayed as an object of ridicule who had frittered away Pounds 2,000 on microscopes that he used for frivolous inquiries, and half a century later Jonathan Swift, in Gulliver's Travels, similarly depicted an academy dedicated to the fatuous pursuit of the minutiae of nature. But these were pin-pricks. The intellectual high ground belonged unequivocally to the practitioners of what contemporaries began to term the "new philosophy". What bound these practitioners, however, is not easy to define. Some proclaimed their modernity by collecting curious artefacts or specimens of the animal or mineral kingdom. Others favoured a Baconian programme of fact-gathering about the practices of artisans. And others again pursued the experimental or mathematical inquiries that we should now recognise most easily as science in its modern sense.

It was in this disparate community, united by a rejection of the dogmatism and rigid systematisation of the old learning but divided on many points of methodology and objectives, that Isaac Newton began his philosophical career in the 1660s. He was in his early twenties at the time, barely graduated from Cambridge. Newton's first and arguably greatest contribution was the discovery of the law of universal gravitation. In the mathematical nature of this discovery he was drawing on a tradition in natural philosophy that takes us back to Galileo, who saw mathematics as the language of the book of nature that he devoted his life to reading, and Galileo's contemporary and fellow Copernican Johannes Kepler.

It was Kepler who demonstrated that the epicycles and other geometrical constructions that complicated both Ptolemy's geocentric system and Copernicus's heliocentric alternative could be done away with by supposing that the planets move in elliptical and not circular orbits round the sun. The challenge for Newton, almost half a century later and with the old crystalline spheres of the medieval world-view a distant memory, was to elucidate a law of attraction between sun and planets that would yield elliptical orbits.

Newton's work in celestial dynamics had its finest expression in the Philosophiae Naturalis Principia Mathematica (1687), a work whose argument rested on the manipulation of such mathematical abstractions as forces acting at a distance between point masses, all in idealised circumstances that had little to do with everyday sense experience. A book of such mathematical rigour spoke obscurely at best to the general reader, and while Newton's other great book, Opticks (1704), was more accessible, it was necessarily through a tradition of semi-popular lecturing and writing that even the highly educated made contact with Newtonian doctrine and accorded Newton the status of a man of genius.

Newton insisted that, as a natural philosopher, he belonged in a tradition with ancient roots, including some, in alchemy and ancient mysticism, that embarrassed certain of his admirers. Although some of the giants on whose shoulders he said he stood were the 17th-century pioneers of the mechanical philosophy, he was no mere elaborator of received opinion. He rejected Descartes's mechanisms and even Boyle's somewhat less fanciful ones as extravagant, preferring to work towards a model founded on attractive forces that acted not only between celestial objects but also between particles of matter and explained phenomena as diverse as chemical reactions, fermentation and the refraction and diffraction of light. It was, in fact, the capaciousness of Newton's world-view that set him apart. In uniting his always cautious reflexions on mechanical explanations with the abstract mathematical analysis of the Principia and a respect for experimental evidence of the kind he described in Opticks, he offered a synthesis of the main strands that had emerged in the scientific revolution.

But Newton did far more than bring the debates and practices that had transformed 17th-century perceptions of nature into a single coherent scheme. As Newton always insisted, his world-view was replete with loose ends as well as certain truths. The open questions were, in fact, a stimulus rather than a fault, and neither they nor Newton's difficult and depressive temperament prevented him from becoming a towering influence on the 18th century. Alexander Pope, a quintessential man of the Enlightenment, expressed his personal awe at Newton's genius in a famous couplet: "Nature and Nature's laws lay hid in night;/ God said, Let Newton be! and all was light." In doing so, he was giving poetic expression to a sentiment from which only the most entrenched critics of the scientific spirit of the 18th century would have dissented.l Robert Fox is professor of the history of science at the University of Oxford. He is the author of numerous works on European science and technology since the 17th century.

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