The Scientific Revolution and the Enlightenment

The relationship between the Scientific Revolution and the Enlightenment is one of the most consequential in the history of modern thought, and one of the most frequently mis-stated. The conventional account says that the seventeenth century produced the new science, and the eighteenth century, taking the new science as model, extended its methods to politics, society, and human nature. There is something right about this. There is also a great deal missing. The Scientific Revolution was, in its own time, deeply contested and strange — populated by magicians, alchemists, court physicians, and heretics as well as by the well-behaved natural philosophers of the textbook. The Enlightenment’s Newton is the Newton who helped the philosophes argue about God and society. The real Newton spent more time on biblical chronology than on calculus.

The success of seventeenth-century natural philosophy — the mathematical description of planetary motion, the unification of celestial and terrestrial physics, the development of experimental method — did not merely add to human knowledge. It changed what human beings thought they could know, and it suggested that the methods that had transformed the study of nature could be applied to the study of society, government, and human nature itself. The thinkers of the Enlightenment were deeply engaged with the new science. Some were practicing scientists; others were popularizers, critics, and philosophical interpreters. Together, they constructed a vision of human reason as a tool for understanding and improving the world — a vision that has shaped the modern age.

The Scientific Revolution: A Brief Overview

The Scientific Revolution is conventionally dated from the publication of Nicolaus Copernicus’s De revolutionibus orbium coelestium (1543) to the publication of Isaac Newton’s Philosophiæ Naturalis Principia Mathematica (1687), though the influence of the revolution continued to be felt throughout the eighteenth century and beyond. The dates are conventional. They are also somewhat arbitrary. There was no moment when the “revolution” happened; there was a long, contested process of change in the methods, content, and institutional organization of natural philosophy that set the stage for everything that came after.

The Copernican Revolution

The traditional medieval view of the cosmos, derived from Aristotle and Ptolemy, placed the Earth at the center of a finite, hierarchically ordered universe. The heavens were perfect, unchanging, and moved by spiritual intelligences; the Earth was the realm of change, decay, and corruption. This view, although modified by medieval and Renaissance astronomers, remained broadly intact until the sixteenth century. It is worth noting that the Aristotelian cosmos was not, on the whole, a parochial or even particularly religious picture. It was a sophisticated natural philosophy that had been worked out by the Greeks, refined by medieval Islamic astronomers, and integrated into Christian theology largely as a matter of convenience. To displace it was to displace, eventually, the whole of medieval natural philosophy — which is what happened.

Copernicus proposed a heliocentric model in which the Earth was a planet, and the planets circled the Sun. The model was not new in itself — Aristarchus had proposed it in antiquity — but Copernicus’s mathematical treatment was detailed, systematic, and difficult to dismiss on technical grounds. De revolutionibus was published in 1543, with a famous preface (probably not by Copernicus himself) claiming that the heliocentric model was a mere calculating device, not a description of physical reality. The claim did not save the book from the censure it eventually received. Copernicus’s work was followed by a series of refinements: Tycho Brahe’s meticulous observations, Johannes Kepler’s laws of planetary motion, and Galileo’s telescopic discoveries, all of which strengthened the heliocentric case.

The deeper significance of the Copernican Revolution was not the displacement of the Earth from the center of the universe, but the demonstration that the inherited cosmological picture could be wrong. The Aristotelian cosmos had been the most thoroughly integrated and authoritative element of the medieval worldview. Once it was replaced, every other element of the inherited system became open to reconsideration. This is the structural reason the Scientific Revolution mattered: it established, as a matter of common practice, that the consensus of the ancients could be wrong, and that human reason could demonstrate the fact.

Galileo and the New Physics

Galileo Galilei (1564–1642) was the great publicist of the new science. His telescopic observations — of the moons of Jupiter (the four “Medicean stars,” named after Galileo’s patron, which is a reminder that even the most famous discoveries of the Scientific Revolution were wrapped up in court politics), the phases of Venus, the craters of the Moon, the sunspots — provided direct evidence for the Copernican view. His Dialogue Concerning the Two Chief World Systems (1632) presented the debate in clear, accessible form and provoked the famous condemnation by the Roman Inquisition. Galileo, who had been a good Catholic all his life, was forced to recant his Copernican views, was sentenced to house arrest, and was, according to a story probably invented in the nineteenth century, heard to mutter “and yet it moves.” The Dialogue was put on the Index, where it remained until 1835.

Galileo’s work on motion — the laws of falling bodies, the principle of inertia, the parabolic trajectory of projectiles — laid the foundations of the new physics. Together with Descartes’s mechanistic philosophy, this work paved the way for Newton’s grand synthesis. The Two New Sciences (1638), published in Leiden because no Italian publisher would touch it, is the founding document of modern mechanics. It is also, in its dialogue form, a work of literature.

The New Method

The Scientific Revolution was as much about method as about content. Francis Bacon’s Novum Organum (1620) outlined an inductive method based on careful observation and the gradual accumulation of natural facts. René Descartes’s Discourse on Method (1637) outlined a deductive method that began with clear and distinct ideas and proceeded by rigorous logical deduction. The mechanical philosophy of Descartes and others rejected occult qualities, sympathies, and Aristotelian teleology in favor of explanation by matter in motion.

These methodological innovations were as important as the substantive discoveries. They suggested that natural philosophy could be reorganized as a collective, cumulative enterprise, and they provided a model for what disciplined human reason could achieve. The Enlightenment would later attempt to apply these methods to the human, social, and political worlds. Whether the methods in fact transferred is, in retrospect, a more complicated question. The social sciences of the nineteenth century were less scientific than their founders hoped, and the predictive ambitions of the early Enlightenment have, in most respects, not been met. The aspiration is what mattered most, and the aspiration is still alive.

The Newtonian Synthesis

Isaac Newton’s Principia (1687) and Opticks (1704) provided a comprehensive mathematical account of motion, gravitation, and light. The law of universal gravitation unified celestial and terrestrial mechanics under a single set of equations. The Opticks combined careful experiment with a tentative, Baconian approach to natural philosophy. The Principia was, by general agreement, the greatest work of natural philosophy ever published. It is also, in its actual contents, a more difficult book than its reputation suggests; the Principia is written in a deliberately archaic geometry, with calculus hidden in the back as the “method of fluxions,” and even competent mathematicians of the eighteenth century were sometimes reduced to arguing about what Newton had actually proved.

Newton became the great symbol of the new science. In France, Voltaire popularized his work and his image, and the French philosophes treated him as a secular prophet. The success of Newton’s enterprise was widely understood as a vindication of reason, and it inspired the conviction that the methods of natural science could be extended to the study of human affairs. It is worth pausing on the fact that the Newton of the philosophes is a simplified Newton, and that the more interesting Newton — the alchemist, the theological obsessive, the manager of the Royal Mint who prosecuted counterfeiters with great zeal — is a Newton the Enlightenment preferred not to think about.

The Philosophes and Science

The French philosophes were deeply engaged with the new science. They translated, popularized, and extended the work of Newton and his successors, and they used the success of natural science as a model for the reform of society. The relation is sometimes described as if the philosophes were spreading Newton’s ideas. The reverse is closer to true: the philosophes used Newton for their own purposes, and the Newton who came into existence in eighteenth-century France was, in many respects, a French invention.

The Newtonian Moment

The French reception of Newton is one of the great stories of eighteenth-century intellectual life. Voltaire’s Letters on the English Nation (1733) introduced a wide French audience to Newton’s work, and his Elements of Newton’s Philosophy (1738), written with the help of his partner Émilie du Châtelet, provided a more systematic presentation. The two were a formidable pair. Voltaire was the famous one, with the prose and the platform. Du Châtelet was the serious one, with the mathematics and the patience. The Elements is more a popularization than a work of original science, but it is a very good popularization.

Du Châtelet (1706–1749) was one of the most important scientists of the eighteenth century. Her translation of Newton’s Principia into French, published posthumously in 1759, is still the standard French translation. She also wrote her own philosophical work, including the Foundations of Physics (1740), which attempted to integrate Newtonian mechanics with Leibnizian metaphysics; it is, in the judgment of more recent historians of science, more original than it was once taken to be. Du Châtelet died in 1749, at the age of forty-two, after the birth of her daughter; the Principia translation was published ten years later, in 1759, with a dedication to her own daughter. The image of du Châtelet at Cirey, sitting in her library working through Newton in French, with Voltaire either helping or interrupting, is one of the underappreciated images of the Enlightenment.

The Encyclopedia Project

The Encyclopédie of Diderot and d’Alembert, published between 1751 and 1772, was a comprehensive summary of contemporary knowledge, and it treated science as one of its central concerns. D’Alembert’s Preliminary Discourse (1751) provided a sophisticated philosophical analysis of the structure of scientific knowledge, distinguishing among the sciences of nature, mathematics, and the arts. The article on “Aiguille” (the needle, as in magnetic compass) was, characteristically, a careful description of the instrument; the article on “Âme” (soul) was, equally characteristically, a manifesto for a materialist account of mind. The encyclopedia, in short, was politically charged in places where most readers would not have noticed.

The Encyclopédie was a collective enterprise, drawing on the work of the most advanced scientists, engineers, and technicians of the day — d’Alembert on mathematics, the Chevalier de Jaucourt on natural history, Louis de Jaucourt on everything else (he contributed over 70,000 articles, a fact that almost no one can believe until they look it up). It was also a politically charged project, repeatedly suppressed and censored by the French authorities, and it became a symbol of the Enlightenment commitment to the free circulation of knowledge. The privilège was revoked in 1759, and from then on the work was produced under perpetual threat of suppression, with printing in Paris, distribution in Lyon, and (often) printing in Neufchâtel as well. The publication history is, by itself, a history of the politics of knowledge in the eighteenth century.

The Science of Man

Enlightenment thinkers were not content with the natural sciences. Inspired by the success of Newton, they sought to develop a “science of man” — a systematic, empirical study of human nature, society, and history.

This project produced a remarkable range of works. Montesquieu’s Spirit of the Laws (1748) compared political systems in a quasi-scientific way. Hume’s Treatise of Human Nature (1739–1740) attempted to apply experimental method to the study of human cognition and morality. Adam Smith’s Theory of Moral Sentiments (1759) and Wealth of Nations (1776) developed systematic accounts of moral and economic behavior. Condillac’s Treatise on Sensations (1754) and Helvétius’s On Mind (1758) developed materialist and sensationalist psychologies.

The “science of man” was enormously productive, but it was also contested. Critics pointed out that human beings differed from physical objects, and that the methods of natural science could not simply be transferred to the study of society. The great German philosopher Immanuel Kant attempted to define the proper limits of this kind of inquiry in his Idea for a Universal History with a Cosmopolitan Aim (1784) and other works. Vico, in the Scienza nuova (1725), had argued, in a different idiom, that the human world is in some sense made by human beings, and therefore intelligible to them in a way that the natural world is not. The debate continues, in different form, in the philosophy of social science today.

The Institutional Dimensions of the Scientific Revolution

The Scientific Revolution was not only an intellectual event but also an institutional one. The new science required new kinds of institutions to support it: laboratories, observatories, scientific societies, and eventually universities reorganized around the new knowledge. The institutions often outlast the ideas that brought them into being, and the modern research university, the modern scientific journal, and the modern research institute are all descendants of the eighteenth-century institutional settlement.

The Royal Society and the Academies

The Royal Society of London, founded in 1660, was the model for a new kind of scientific institution. It was a voluntary association of “natural philosophers” who met regularly to hear papers, conduct experiments, and correspond with fellow members. It published the Philosophical Transactions, the first scientific journal, and it served as a model for similar institutions across Europe. The Society had, in its early decades, something of the quality of a club: meetings were conducted partly in English and partly in Latin, and there was a long debate, only partly resolved, about whether the Society’s job was to do science or simply to talk about it.

The French Academy of Sciences, founded in 1666, was a state-supported institution with a salaried body of members. The Berlin Academy, the Saint Petersburg Academy, and other Continental institutions followed similar models. The Académie française, although devoted to language and literature, contributed to the institutional infrastructure of Enlightenment intellectual life.

Universities, Salons, and Publics

The new science spread through a network of institutions that included not only the academies but also the universities, the salons, the coffeehouses, the Masonic lodges, and the periodical press. Each of these spaces provided an arena in which scientific ideas could be discussed, tested, and disseminated.

The salons, in particular, were important venues for the integration of science into Enlightenment culture. The most famous, including those of Madame Geoffrin (whose salon in the Place des Victoires met on Mondays for the philosophers, Wednesdays for the artists — a careful segregation of the intellectuals from the painters), Madame d’Épinay, and the Baron d’Holbach, brought together philosophers, scientists, writers, and aristocrats in regular gatherings that combined conversation, experiment, and entertainment. The salon of Madame du Châtelet and Voltaire at Cirey was, in a sense, the prototype of all the rest: a private intellectual space in which serious work was done but in which the work was disguised as social life.

Encyclopedias and Public Knowledge

The eighteenth century saw a flood of encyclopedic projects. The Cyclopaedia of Ephraim Chambers (1728), the Encyclopédie of Diderot and d’Alembert (1751–1772), the Encyclopaedia Britannica (1768–1771), and many smaller works attempted to organize and disseminate the new knowledge. These projects were technically challenging, commercially significant, and politically charged, and they helped create a public for science that extended well beyond the universities and academies. The Encyclopédie’s subscription list of about 4,000 was enormous for the period; the Britannica’s was smaller, but its eventual commercial success was greater. Notice that the very idea of an encyclopedia, accessible to a paying public, is an Enlightenment invention. The medieval encyclopedia had existed, but the selling of comprehensive knowledge to a mass market is a new thing in the eighteenth century.

Science and Religion

The relationship between the new science and traditional religion was one of the central problems of the Enlightenment. The Scientific Revolution had made it possible to believe that the natural world operated according to discoverable laws, but it was less clear what this meant for the existence of God, the reality of miracles, and the authority of scripture. The relation is more interesting than the simple story of “conflict” suggests. Most Enlightenment thinkers were not anti-religious; most religious thinkers were not anti-science. The hard cases, where there is genuine conflict, are the famous ones (Galileo, the publication of the Encyclopédie); the ordinary cases, in which scientists went to church and bishops read Newton, are less dramatic but more representative.

The Mechanistic Universe and the Argument from Design

The mechanistic philosophy of Descartes and his successors treated the natural world as a vast machine, governed by the laws of motion and collision. This picture raised a famous question: who designed the machine? The argument from design — that the apparent order and complexity of the universe pointed to a divine designer — was developed in detail by Robert Boyle, John Ray, and William Paley, and it became one of the most influential arguments for the existence of God in the eighteenth and nineteenth centuries. Paley’s Natural Theology (1802) is the classic statement: someone crossing a heath who found a watch would infer a watchmaker; the universe is at least as intricate as a watch, and so we may infer a universe-maker.

This version of natural theology was compatible with deism, the view that God created the universe and its laws but did not intervene in history. Many Enlightenment thinkers, including Voltaire, Franklin, and Jefferson, were deists of this kind. The argument, of course, was never as conclusive as it looked. The watchmaker analogy begs the question; the actual mechanics of design (the “design” in nature is, in many cases, contingent rather than engineered) is more complex than Paley admitted; and the move from a designed universe to a designer-God who deserves the devotion of human beings requires an additional step that the argument does not in fact take.

Skepticism and the Critique of Natural Theology

The mechanistic universe also raised the possibility that it might have come into being without a designer. The ancient atomism of Democritus and Epicurus, revived in the seventeenth century by Pierre Gassendi and others, suggested that a complex world could be the result of purely material processes.

Hume’s Dialogues Concerning Natural Religion (1779) subjected the argument from design to a withering critical examination, concluding that arguments from observed order to a divine cause were much weaker than they appeared. The work of the Baron d’Holbach, in the System of Nature (1770), and of La Mettrie, in Man a Machine (1747), pushed further toward a fully materialist and atheist account of nature. Hume’s Dialogues were, of course, published posthumously; the publisher (William Strahan) was terrified of the consequences; the manuscript was entrusted to Adam Smith, who held it for years and finally arranged for it to appear in 1779, three years after Hume’s death.

Science and Religious Toleration

The new science also had implications for religious toleration. By demonstrating that the Bible could be interpreted in different ways, and that the natural world could be understood without the help of theological categories, the new science contributed to the emergence of a more pluralistic and skeptical attitude toward religious authority.

The story of Galileo and the Church became a symbol for many Enlightenment thinkers of the dangers of religious interference with science. The case was used by Voltaire, by Diderot, and by the authors of the Encyclopédie to argue for the autonomy of scientific inquiry. The case was, on the historical evidence, more complicated than the Enlightenment version makes it. Galileo was a courtly Catholic with a complicated relationship with the Roman authorities; the Index condemnation of the Dialogue was the work of a particular faction, which lost to another faction; and the famous “and yet it moves” was almost certainly a later invention. What the story represents, however — the principled resistance of a free inquiry to a conservative religious authority — was real, and is what made it politically useful.

Science and Politics

The political implications of the new science were also significant. Enlightenment thinkers frequently drew analogies between the new science and the proper organization of political life. The analogies were often more rhetorical than substantive; the assumption that the political world could be studied in the same way as the natural world has not, in fact, paid off. But the image of the political world as a kind of machine to be set in order by a competent engineer has been a powerful political image, and it remains in use.

The Natural Order and Natural Law

The idea that the natural world operated according to discoverable laws was closely connected to the idea of natural law in politics. The natural-law tradition, going back to the Stoics and the medieval jurists, held that there were moral principles accessible to human reason that bound all human beings. Enlightenment thinkers combined this older tradition with the new natural philosophy to argue that the laws of politics and morality could be studied in a similarly systematic way.

The political philosophy of John Locke is a paradigm case. Locke’s account of natural rights and his theory of government were based on a conception of human nature that owed as much to the new philosophy of nature as it did to the older natural-law tradition. Locke’s theory of property, in the Second Treatise, is built on a quasi-scientific account of the labor that creates value; his theory of consent is built on a quasi-scientific account of the social contract as a real (or, in the modern reading, as a hypothetical) historical event. The mixture is characteristic of the period.

The Republic of Letters and International Science

The new science was an international enterprise. Newton corresponded with Leibniz (in one of the great priority disputes of the early eighteenth century, Leibniz accused Newton of having stolen the calculus; Newton responded by setting up a committee of the Royal Society to investigate; the committee concluded, unanimously, that Newton had priority — an outcome that, given the committee was loaded with Newton’s allies, surprised no one except Leibniz). Voltaire corresponded with Frederick the Great. Franklin corresponded with members of the Académie des sciences. This international network of correspondence and exchange helped create a sense of common intellectual purpose that transcended national and religious boundaries.

It also helped generate a set of practical institutions — learned societies, scientific journals, international projects — that served as a model for the cosmopolitan ideals of the Enlightenment. Kant’s essay Perpetual Peace (1795) imagined a future world order in which the republican nations of the world would be bound together by trade, law, and the free exchange of knowledge. The United Nations and the European Union are, in their bureaucratic logic, descendants of this vision, even when they are the descendants that the founders would have disowned.

Science, Industry, and Useful Knowledge

The new science was closely connected to the development of useful knowledge. Bacon had argued that the purpose of natural philosophy was the relief of the human condition, and the Enlightenment carried on this program. The Encyclopédie included extensive articles on agriculture, manufacturing, mining, and other practical arts. The Scottish Enlightenment was particularly concerned with what Smith called the “progress of opulence” — the gradual improvement of material life through the application of science and industry.

The relationship between science and industry was not without tensions. Many Enlightenment thinkers were wary of the social effects of industrialization, and Rousseau in particular worried that the arts and sciences had produced luxury and inequality rather than human happiness. But the overall trend was toward an increasing integration of scientific knowledge with the productive arts, and this integration would eventually transform the modern world. The Industrial Revolution, which began in the 1770s and gathered force through the eighteenth century, was, in its origins, a revolution in the application of Enlightenment science to industrial production. Whether that is to be celebrated or mourned is, of course, a different question.

Science and Modern Education

The Scientific Revolution had a profound impact on the organization of education. The old universities had been structured around the medieval trivium and quadrivium, with theology as the queen of the sciences. The new science, along with the new philosophy, called for a different arrangement.

The Reform of the Universities

The reform of the universities was a major preoccupation of Enlightenment reformers. The Scottish universities of Edinburgh and Glasgow, reformed in the eighteenth century, became models of the new academic order, combining rigorous instruction in the sciences with the new experimental philosophy. The German universities, especially Halle, Göttingen, and Königsberg, were also reorganized around the new knowledge. The famous research university of the nineteenth century — the Humboldtian model of teaching and research combined — was a direct descendant of the eighteenth-century German reforms.

The new universities emphasized the study of mathematics, natural philosophy, and the modern languages, and they included subjects — political economy, modern history, natural law — that had been largely absent from the old curricula. The result was a system of higher learning better suited to the practical and intellectual needs of the modern world. Whether the modern world is, in fact, what the reformers wanted is, in the twenty-first century, a question being argued out across the humanities.

The Popularization of Science

The Enlightenment was also a period of extraordinary scientific popularization. Books of popular science, public lectures, demonstration experiments, and periodical articles brought the new knowledge to a wider audience than ever before. Voltaire, Fontenelle, and later writers such as Joseph Priestley and Erasmus Darwin were among the most popular scientific writers of the period. Fontenelle’s Entretiens sur la pluralité des mondes (1686) — dialogues between a philosopher and a marquise about astronomy, written for a general audience and translated into every European language — was, in its own way, a founding text of the genre.

The popularization of science was closely connected to the broader project of Enlightenment. To make science accessible was to make reason accessible, and to make reason accessible was to prepare the way for the reform of institutions and the improvement of the human condition. The premise, of course, is that access to reason leads to improvement. That premise is one of the things the twentieth century taught the heirs of the Enlightenment to be skeptical about. It is also one of the things that the heirs of the Enlightenment cannot give up, because the alternative is to give up the Enlightenment, and they have not found a successor they can live with.

The Legacy of the Scientific Revolution and the Enlightenment

The legacy of the Scientific Revolution and the Enlightenment is the world we live in. The methods of modern science, the institutions of scientific research, the moral vocabulary of human rights, the political institutions of liberal democracy — all of these are descendants of the eighteenth-century fusion of natural science and Enlightenment philosophy.

This legacy is not without complications. The confidence of the eighteenth century in the universality of human reason has been challenged by the romantic, postcolonial, and postmodern critics of the Enlightenment. The environmental costs of industrialization, the political disasters of the twentieth century, and the persistence of deep inequalities have made it harder to maintain a simple faith in progress. Whether the Enlightenment’s confidence was ever the right confidence is now a serious question, and one that serious scholars take seriously.

But the achievements of the eighteenth century cannot be dismissed. The fact that human beings have been able to understand the natural world, to develop effective medical treatments, to communicate across vast distances, to design institutions that protect individual liberty, and to organize international cooperation on scientific questions is, in significant part, a result of the long scientific and intellectual revolution that began in the sixteenth century and reached its political climax in the eighteenth. The Enlightenment is not the only thing that produced these achievements, and the connection between, say, the steam engine and Rousseau’s Social Contract is not straightforward. But the institutional and intellectual conditions under which the achievements became possible are recognizably Enlightenment conditions.

The contemporary world, with its climate change, its emerging technologies, and its global challenges, has only increased the importance of this inheritance. To be heirs of the Scientific Revolution and the Enlightenment is to inherit both the great achievements of the modern world and the great responsibilities of continuing the work of building a rational, just, and sustainable human community. Whether the work can be completed with the inherited tools is, of course, a question. The fact that the question can be put, and the tools used to put it, is itself a sign of the inheritance.

The Scientific Revolution and the Enlightenment: How Science Shaped Modernity