Profiles of the major figures of the Scientific Revolution—Copernicus, Tycho Brahe, Kepler, Galileo, Descartes, Bacon, Boyle, Hooke, Huygens, Newton, and Leibniz.

Key Figures of the Scientific Revolution: The Minds That Rebuilt Nature

The Scientific Revolution did not arrive from nowhere, and it did not arrive in the mind of a single thinker. It was the cumulative achievement of a cast of distinct personalities scattered across sixteenth- and seventeenth-century Europe — a Polish canon, a Danish astronomer with a gold nose, a German mystic-mathematician, an Italian who liked a good argument, an English lord chancellor, a French soldier-philosopher, and an English professor who may or may not have watched an apple fall. Their biographies, arguments, friendships, and feuds together produced one of the most consequential transformations in human history: the replacement of the Aristotelian-Ptolemaic cosmos with a universe governed by impersonal, mathematically describable laws. This page offers a comprehensive overview of those figures. It is the gateway to the more detailed pages on Nicolaus Copernicus, Johannes Kepler, Galileo Galilei, Isaac Newton, and the methodological duo of Francis Bacon and René Descartes. For the broader context in which these figures worked, see the page on the Scientific Revolution itself, and for the empirical content of their discoveries, the section on major discoveries of the era.

A Note on “Who Counts”

A list of “key figures” is necessarily selective. The scholars treated in depth here are the ones whose names are inseparable from the central narrative: the heliocentric revolution, the new astronomy, the new physics, and the new philosophy of nature. Many other figures are mentioned in passing — Tycho Brahe the observer, Robert Boyle the chemist, Robert Hooke the polymath, Christiaan Huygens the Dutch mathematician, and Gottfried Wilhelm Leibniz the universal genius — because they appear at crucial moments in the stories of the principals. A complete list would be far longer and would include Paracelsus, Vesalius, Harvey, Gilbert, Gassendi, Pascal, Mariotte, and many others. What unites the figures on this page is that each of them, in his own way, helped to articulate a new picture of nature. They were not all scientists in the modern sense. Copernicus was a churchman; Galileo was a courtier; Newton was an alchemist; Bacon was a politician; Descartes was a soldier. The Scientific Revolution, in other words, was not the work of professionals in a discipline called “science.” It was the work of educated Europeans with access to a shared classical inheritance, the printing press, and the patronage of courts, churches, and universities, who collectively decided that the book of nature should be rewritten.

Nicolaus Copernicus (1473–1543)

The revolution began quietly in northern Poland. Nicolaus Copernicus was born in 1473 in the Royal Prussia region of the Kingdom of Poland, the son of a merchant and a niece of the bishop of Warmia. He was educated at the University of Kraków and then at the universities of Bologna and Padua, where he studied canon law and medicine but also lingered long enough to read Ptolemy. By 1503 he held a doctorate in canon law and had been elected a canon of the cathedral of Frombork — a comfortable ecclesiastical post that he would keep for the rest of his life. Copernicus’s famous innovation, the heliocentric theory, is treated in detail on the Copernicus page. Briefly: sometime around 1510 he circulated a short manuscript, the Commentariolus, claiming that the apparent motions of the Sun, Moon, and planets could be explained more economically if the Earth were assumed both to rotate on its axis and to revolve, together with the other planets, around a central Sun. The full argument appeared only at the end of his life, in De Revolutionibus Orbium Coelestium (1543), published with a famous anonymous preface by the Lutheran theologian Andreas Osiander that presented the new model as a mere calculating device rather than a physical claim about the cosmos. Copernicus is said to have received a copy of the printed book on his deathbed in May 1543. Copernicus was the figure who started the chain reaction, but he was not its most dynamic proponent. He was a cautious, mathematically conservative thinker. His system still used circular orbits and epicycles, and his insistence on uniform circular motion was, if anything, an obstacle to accurate prediction. For the full structure and consequences of his book, see What Did Copernicus Write in De Revolutionibus? and How Did Copernicus Change Astronomy?. The social and theological reasons his theory was so controversial are explored in Why Was Copernicus’s Theory Controversial?.

Tycho Brahe (1546–1601)

The man whose observations made the next step possible was not, strictly speaking, a Copernican. Tyge Ottesen Brahe — known as Tycho — was a Danish nobleman who, having lost part of his nose in a sword duel as a student, wore a metal prosthesis for the rest of his life. With the patronage of King Frederick II of Denmark, he built two observatories on the island of Hven: Uraniborg and Stjerneborg. There, between roughly 1576 and 1580, he and his assistants compiled the most accurate naked-eye star catalog and the most accurate record of planetary positions that had ever existed — accurate to about one arcminute, which is the angular size of a U.S. quarter coin seen from a hundred meters away. Tycho was a brilliant observer but a stubborn theorist. He rejected both Ptolemy and Copernicus and proposed a “geo-heliocentric” compromise: the Earth sits at the center of the universe, the Sun and Moon revolve around it, and the other planets revolve around the Sun. This Tychonic system preserved the physics of a stationary Earth while incorporating the strengths of Copernicus’s ordering of the planets. The system remained popular among Catholic astronomers in the early seventeenth century, in part because it was less obviously incompatible with scripture. Tycho’s importance is mostly indirect. Disinherited by the new Danish king, he moved to Prague in 1597 and took on a young German assistant, Johannes Kepler, to whom he entrusted his life’s observations. After Tycho’s death in 1601, Kepler used the data to derive the elliptical orbits that Copernicus’s circular-mindedness had been unable to find.

Johannes Kepler (1571–1630)

If Copernicus began the revolution and Tycho supplied the data, Johannes Kepler supplied the mathematics. Kepler was born in 1571 in Weil der Stadt, in present-day Baden-Württemberg, and educated at the University of Tübingen, where he defended Copernicus in a public disputation. The rest of his life was a long, painful struggle with mathematics, mysticism, patronage, personal loss, and the sheer difficulty of forcing Tycho’s data into a Copernican mold. Kepler’s three laws of planetary motion are described on the Kepler page and in detail at What Are Kepler’s Three Laws of Planetary Motion?. In short, the laws state that the planets move in ellipses with the Sun at one focus; that a line from a planet to the Sun sweeps out equal areas in equal times; and that the squares of the planets’ orbital periods are proportional to the cubes of their semi-major axes. The first two appeared in the Astronomia Nova (1609), the third in the Harmonices Mundi (1619). Together they did something no one had done before: they replaced the geometry of the heavens with a precise kinematics, providing the empirical challenge that Newton’s gravitational theory would eventually meet. The way those laws clinched the heliocentric case is discussed in How Did Kepler’s Laws Support Heliocentrism?. Kepler was also the author of the Mysterium Cosmographicum (1596), which proposed that the five regular solids could be used to explain the number and spacing of the planets — a striking but ultimately fanciful program. He wrote the Rudolphine Tables (1627), which remained the standard planetary tables for a century. He wrote a science-fiction story, the Somnium (1634, posthumous), in which a trip to the Moon allowed him to imagine what the Earth would look like from outside. He was a thoroughgoing Copernican, a Protestant in a Catholic land, and an astrologer who often expressed embarrassment at being paid for casting horoscopes. He died in 1630 in Regensburg, having spent the last years of his life trying to collect small sums owed to him by the Imperial treasury.

Galileo Galilei (1564–1642)

Of all the figures of the Scientific Revolution, none is more famous in the popular imagination than Galileo, and none is more poorly understood. The standard image — the brave scientist defying the Church — is partly true and partly misleading. Galileo was, in fact, a devout Catholic; he was also, in fact, prosecuted by the Inquisition. The story is told on the Galileo page. Galileo was born in Pisa in 1564, the son of a musician and music theorist. He studied medicine at the University of Pisa but switched to mathematics and natural philosophy, eventually holding the chair of mathematics at Padua from 1592 to 1610. These Paduan years were his most productive. He worked out the law of falling bodies, laid the foundations of the science of mechanics, and built a thermoscope. Then, in the summer of 1609, he heard of a Dutch device that made distant objects appear closer, and he built his own refracting telescope — eventually improving it to about thirty times magnification. What he saw with it changed astronomy forever. His telescopic discoveries are described in What Did Galileo Discover With His Telescope?. The Moon was not the smooth, perfect sphere of Aristotelian cosmology; it had mountains and craters. Jupiter had four moons of its own, which Galileo called the “Medicean stars” in honor of his Medici patrons. Venus showed phases, exactly as Copernicus had predicted and the Ptolemaic system could not easily explain. The Milky Way resolved into a swarm of faint stars. The Sun had spots, blemishes on what should have been a flawless heavenly body. In March 1610 Galileo published these results in the Sidereus Nuncius, the “Starry Messenger,” an instant bestseller. Galileo’s contributions to physics proper — the law of falling bodies, the parabolic trajectory, the inclined plane experiments, the principle of inertia — are discussed in How Did Galileo Contribute to Physics?. The combination of careful observation, controlled experiment, and mathematical analysis that Galileo practiced is often taken as the prototype of “modern” science, though in fact he owed as much to Archimedes and the medieval calculatores as to any predecessor. The other half of the Galileo story is his conflict with the Church, which culminated in the trial of 1633. Pope Urban VIII had been an admirer and even a patron. In 1623 Galileo dedicated his Assayer to the new pope, and the pope reportedly told Galileo that he should write about Copernicanism as a hypothesis. But in 1632 Galileo published his Dialogue Concerning the Two Chief World Systems, in which the character of the Pope — the simpleton Simplicio — was made to defend the Ptolemaic view. Urban felt personally mocked. Galileo was tried, found “vehemently suspect of heresy,” forced to abjure, and confined to house arrest for the rest of his life. The events are recounted in Why Was Galileo Put on Trial?. In his final years, blind and ailing, Galileo produced his masterwork of physics, the Two New Sciences (1638), which set out the foundations of the science of strength of materials and the kinematics of uniformly accelerated motion. He died in January 1642, the year Newton was born.

Francis Bacon (1561–1626)

The English contribution to the Scientific Revolution was, in the early seventeenth century, more methodological than mathematical. Francis Bacon — Viscount St Alban, Lord Chancellor of England, brief author of King Lear and Henry VIII before Shakespeare took them over — argued that the proper aim of natural philosophy was not the contemplation of eternal truths but the relief of the human condition. His program of inductive inquiry is treated on the Bacon and Descartes page and in more detail at What Was Francis Bacon’s Scientific Method?. Bacon’s method, set out in the Novum Organum (1620) and earlier in The Advancement of Learning (1605), begins with a critique of Aristotelian syllogism, which he considered sterile. The proper method, he argued, proceeds by patient observation, careful tabulation, and gradual ascent from particulars to axioms. He distinguished four kinds of “idols” — of the tribe, the cave, the marketplace, and the theatre — that warp human reasoning. He envisioned a collaborative research institution in his unfinished utopia, New Atlantis (1627), which he called Salomon’s House. It was a blueprint for the Royal Society, founded in 1660. Bacon is often remembered as the prophet of empiricism, but the label is too narrow. He was also a parliamentarian, a jurist, an essayist, and a politician who fell from power after accepting bribes (he was, technically, the first Lord Chancellor to be convicted of corruption). His method was never, in his own lifetime, systematically applied. But the rhetoric of experiment, of the long haul of data-collection, of skepticism toward inherited authority, became part of the air the new natural philosophers breathed.

René Descartes (1596–1650)

Across the Channel, René Descartes was pursuing a very different program. Where Bacon began with sense experience and tried to reason up from it, Descartes began with the mind and tried to deduce everything from self-evident first principles. Born in La Haye en Touraine in 1596, educated at the Jesuit college of La Flèche, and a soldier in the Dutch and German armies in his twenties, Descartes settled in the United Provinces in 1628 and produced a flood of works that would redirect the philosophy of nature: the Discourse on Method (1637), with its famous “cogito, ergo sum”; the Meditations on First Philosophy (1641); and the Principles of Philosophy (1644). His full contributions are surveyed in How Did René Descartes Contribute to the Scientific Revolution?. Descartes’ central move was the division of reality into two substances: res cogitans, thinking substance, the domain of minds; and res extensa, extended substance, the domain of bodies. The second of these, extended substance, was what physics studied. Descartes reduced the physical world to matter in motion, governed by the laws of impact and conservation of motion, with God supplying the cosmic energy at the beginning. His vortex theory of the solar system held that the planets were carried around the Sun by huge whirlpools of subtle matter — an alternative to Newtonian gravitation that remained influential in France for much of the eighteenth century. Descartes was also a brilliant mathematician. In the Geometry, originally published as an appendix to the Discourse on Method, he developed the method of analytic geometry, plotting equations on coordinate planes. Almost every subsequent figure in the Scientific Revolution, from Newton to Leibniz, worked within a conceptual space Descartes had first mapped. He spent the last years of his life in the service of Queen Christina of Sweden, who is said to have insisted that he give her philosophy lessons at five in the morning in a cold castle library. He died of pneumonia in Stockholm in February 1650.

The Mechanical Philosophy: Boyle, Hooke, Huygens

Between Descartes and Newton, the seventeenth century saw the rise of a self-conscious “mechanical philosophy,” which held that all natural phenomena should be explained in terms of matter, motion, and impact. Three figures stand out. Robert Boyle (1627–1691) was an Anglo-Irish aristocrat and a founding member of the Royal Society. He is best known for Boyle’s Law, the inverse relationship between the pressure and volume of a gas at constant temperature, published in 1662. He was a vigorous champion of the mechanical philosophy and a chemical atomist, arguing that matter was composed of corpuscles of various sizes and shapes whose combinations and motions explained the phenomena of chemistry. His The Sceptical Chymist (1661) attacked the ancient four elements and helped clear the ground for modern chemistry. Robert Hooke (1635–1703) was a brilliant polymath and the first Curator of Experiments at the Royal Society. He worked on mechanics, microscopy, geology, architecture, and astronomy. His Micrographia (1665) introduced the world to the intricate structure of insects, plants, and a slice of cork — the book in which the word “cell” was first used to describe the basic units of living tissue. Hooke also engaged Newton in a long and bitter priority dispute over the inverse-square law of gravitation and over the wave theory of light. Newton, who had a powerful memory for enemies, repaid Hooke in kind. Christiaan Huygens (1629–1695) was a Dutch mathematician, physicist, and astronomer. He was the first to develop the mathematical theory of the pendulum clock (1656), greatly improving timekeeping. He derived the laws of elastic collision (1669), proposed the wave theory of light in his Traité de la lumière (1690), and with his brother Constantijn built powerful telescopes with which he discovered Titan, the largest moon of Saturn, and described the true shape of Saturn’s rings. Huygens was widely regarded as the foremost natural philosopher of his generation, and his death in 1695 was the end of an era.

Isaac Newton (1642–1727)

And then there is Newton. Born in Woolsthorpe, Lincolnshire, on Christmas Day 1642 (old style) — the year Galileo died — Newton came into the world as a premature infant said to be small enough to fit into a quart pot. He survived childhood, attended the King’s School in Grantham, and was admitted to Trinity College, Cambridge, in 1661. The story of his life and work is told on the Newton page. The years 1665 to 1667 were the “plague years,” during which Cambridge was dispersed and Newton returned to the family farm. There, by his own later account, he made the first runs of three great discoveries: the calculus, the composition of white light, and the law of gravitation. He returned to Cambridge, was elected Lucasian Professor of Mathematics in 1669, and for the next two decades corresponded with a widening circle of natural philosophers — Robert Hooke, Edmund Halley, Christopher Wren, and others — about the shape of planetary orbits, the motion of the moon, and the cause of tides. In 1684 Halley visited Newton at Cambridge to ask what curve a planet would trace if attracted to the Sun by a force varying inversely with the square of its distance. Newton replied at once that it would be an ellipse. The story is the opening scene of one of the most consequential books in this history. The book is the Philosophiae Naturalis Principia Mathematica (1687), usually called the Principia or simply “the Principia.” Its contents are surveyed at What Is in Newton’s Principia Mathematica?. In three books, the work laid out the mathematical framework of classical mechanics, derived the three laws of motion, demonstrated Kepler’s empirical laws as consequences of universal gravitation, explained the tides and the motion of the Moon, and extended the analysis to comets and to the figure of the Earth. The famous “Rules of Reasoning in Philosophy” — empirical, conservative, simple — were a working codification of the new mechanical philosophy. The reception of the Principia made Newton the most famous natural philosopher in Europe, and he became President of the Royal Society in 1703, a position he held until his death. The way Newton arrived at universal gravitation — the apple, the correspondence, the unification of celestial and terrestrial mechanics — is the subject of How Did Newton Discover Gravity?. His work on light and color, the prism experiments, the Opticks (1704), and the dispute with Hooke over the nature of light are described in What Did Newton Contribute to Optics?. Newton’s later years were a complex mixture. He was Warden, and then Master, of the Royal Mint; he presided over the recoinage of English silver with extraordinary energy; he was knighted in 1705. He engaged in a long and bitter priority dispute with Leibniz over the invention of the calculus, a dispute that damaged the reputations of both men and, in the English-speaking world, delayed the adoption of Leibniz’s superior notation. He wrote extensively on alchemy and biblical chronology, subjects he kept carefully private. He died in Kensington on 20 March 1727 and was buried in Westminster Abbey. His epitaph, by Alexander Pope, was: “Nature and Nature’s laws lay hid in night: / God said, Let Newton be! and all was light.”

Gottfried Wilhelm Leibniz (1646–1716)

A separate page could be written about Leibniz — mathematician, logician, diplomat, historian, and philosopher — but a few words belong here. Born in Leipzig in 1646, Leibniz entered the University of Leipzig at fourteen, earned a doctorate at twenty, and spent the rest of his life in a dizzying round of courts and projects. He served the Elector of Mainz, the House of Hanover, and briefly the Tsars in St Petersburg. He co-founded the Berlin Academy of Sciences. Independently of Newton, Leibniz developed the differential and integral calculus, published first, in 1684, and used a notation (dx, dy, the integral sign) that was so much more flexible than Newton’s fluxions that it became standard across the Continent. He proposed the principle of sufficient reason, the law of continuity, and the doctrine of monads — the claim that the universe is composed of simple, indivisible, perception-bearing units. He argued, against Newton’s absolute space and time, that space and time are relations among objects. He invented a calculating machine that could multiply and divide, designed a windmill, proposed a system of international languages, and wrote voluminously on almost every subject. He died unhappily in Hanover in 1716, his funeral attended by exactly one colleague.

One of the most underappreciated features of the Scientific Revolution is that the figures involved were not, at the start, a self-conscious professional class. They were churchmen, courtiers, professors, physicians, and gentlemen. Copernicus was a canon; Galileo was a court mathematician to the Medici; Descartes was a private gentleman; Newton was a university professor but with a side career at the Mint. The “scientist” as a professional identity did not exist. The word itself, scientist, was coined only in 1833, by William Whewell. The Royal Society of London, founded in 1660, and the Académie Royale des Sciences, founded in Paris in 1666, were the first bodies explicitly devoted to experimental natural philosophy. They were small, often quarrelsome, and politically vulnerable. Their members came from the landed, mercantile, and professional classes; they met in lecture halls, coffeehouses, and private houses. They published in the new periodical press, the Philosophical Transactions (1665) and the Journal des sçavans (1665) being the first. The instruments they used — air pumps, telescopes, microscopes, thermometers, barometers, vacuum chambers — were increasingly supplied by London instrument-makers like Hooke’s associate Christopher Cock. The religious framing of natural philosophy also changed. Newton and Boyle, in particular, were deeply devout, and they presented the new science as a way of reading the “Book of Nature” alongside the Book of Scripture. The argument from design — that the regularity of nature testified to the wisdom of the Creator — was a powerful tool for making experimental philosophy respectable. By the end of the seventeenth century, the mechanical philosophy had not displaced religion; it had become a support for a particular kind of natural theology. For the broader social and religious consequences of these developments, see the section on the impact of the Scientific Revolution on society and, in particular, the page on religion and the Church.

The Revolution in Method

A theme that runs through all of the figures treated here is the slow emergence of a shared sense of how natural philosophy ought to be done. By the early eighteenth century, the consensus looked something like this: collect observations, prefer measurement and experiment, formulate hypotheses mathematically, test them against further observation, prefer simple explanations, and remain skeptical of inherited authority. None of the principals followed all of these rules all of the time, but the cumulative effect of their practice was to change what counted as a good argument in natural philosophy. The deeper philosophical background to this methodological shift is explored in the section on the Scientific Revolution’s origins and causes and in its section on the philosophy of science. There was no single moment at which the revolution was “complete.” It is more useful to think of a long arc, beginning with the cautious Polish canon and ending with the publication of the Principia. Within that arc, the figures on this page were the principal actors. Their discoveries are surveyed in the section on major discoveries of the era, and the controversy surrounding the heliocentric theory in particular is treated in the heliocentrism and astronomy section.

Reading the Figures Together

The advantage of treating the figures one at a time is that each becomes vivid. The advantage of treating them together is that one sees the pattern. Copernicus began a conversation about the structure of the cosmos. Tycho provided the data with which the conversation could be settled. Kepler mathematized the result. Galileo observed the new cosmos and began to construct the new physics. Bacon articulated the method; Descartes articulated the metaphysics. Boyle, Hooke, and Huygens elaborated the program. Newton closed the circle by showing that the same laws governed the heavens and the Earth. Leibniz, last of the giants, took the new tools into every corner of thought and argued about the consequences with Newton himself. The figures argued with each other, sometimes with bitterness. Galileo did not read Kepler carefully. Descartes ignored the English experimentalists. Newton quarreled with Hooke, with Flamsteed, and with Leibniz. Their quarrels were not a distraction from the science; they were a part of it. The Scientific Revolution was, among other things, a long argument among brilliant men about how to think about nature, and the argument produced the world we have inherited.

Key Figures of the Scientific Revolution: Minds That Rebuilt Nature