The Age of the Baroque and Enlightenment 1600-1800: Philosophy

Arts and Humanities Through the Eras. Editor: Edward I Bleiberg, et al. Volume 5. Detroit: Gale, 2005.

Baroque Philosophical Roots

Protestant Vs. Catholic Science

During the twentieth century historians often debated the question of the relationship between religion and the rise of science. Following the lead of the sociologist Max Weber, who had argued that there was a positive connection between Protestantism and the rise of capitalism in Europe, one group of historians made the case that Protestant culture was far more encouraging of scientific research than was Catholic culture. The problem with their case was that while England and Holland—the two examples most often cited in support of the argument—were Protestant, these were also states where the power of the state church was seriously constrained by the government. In Protestant states where the church and government shared the same cultural and religious agenda, such as the German Protestant states of the Central European Holy Roman Empire, scientific research was as absent as it was in Catholic states. An inability on the part of the state church to repress scientific research appears to have been more important than any positive encouragement given to science by Protestant churchmen.

The Crime of Galileo

The story of Galileo has often been used to suggest that Catholicism was more hostile to science than Protestantism was. Galileo Galilei (1564-1642), known as the great Italian “natural philosopher,” was a scientist who was forced by the Roman Inquisition to recant his arguments in support of the Copernican thesis that the earth revolves around the sun. Yet as Catholic apologists for the Inquisition have pointed out, Galileo was arguing for more than just the Copernican thesis, the notion that the sun rather than the earth was the center of the universe. His work presented a challenge to the church because he was promoting the notion that scientific pursuits should be free from moral and religious scrutiny. No seventeenth-century Christian church was, in fact, willing to grant that science should have such independence. Galileo’s case for the autonomy of science, though, has long made him the starting point for any discussion of philosophy in the age of the Baroque. Galileo followed a string of Renaissance humanists who saw the “book of Nature” as an alternative to the teachings of medieval scholasticism. Tommaso Campanella (1568-1639), one of Galileo’s contemporaries, went so far as to contrast the arid emptiness of traditional medieval scholasticism with its Aristotelian science, with nature as the true “living book of God.” Galileo, though, was the first scientist to lend the weight of his achievements and observation to his argument. Although he was already well known for his discoveries of the physical properties of motion, Galileo had begun in 1609 to channel his considerable research talents into proving that the Copernican thesis was correct. After lifelong study, Nicolaus Copernicus published his heliocentric theory in 1543, the same year in which he died. Like most Renaissance astronomers, his work was not based upon scientific observation or experimentation, but on his knowledge of texts, combined with his own subtle theorizing. Although his theory had circulated relatively freely in the sixteenth century, it did not become controversial until Galileo decided to confirm its observations with the use of a telescope. Galileo had read about this new invention, and he figured out how to build one himself. Then he wrote The Starry Messenger (1610) based upon the observations he made with it. Churchmen were fascinated with Galileo’s new instrument; however, they did not follow him in his conclusion that the evidence it revealed refuted the Ptolemaic thesis that the sun revolved around the earth. In 1616, Galileo was called before the Inquisition and told to stop teaching that the Copernican thesis was true. He agreed, but then continued to try to convince churchmen and other intellectuals of the error of their ways. In 1623 he published another book, The Assayer, ostensibly a report of his observations on comets, but in fact an attack on the Ptolemaic thesis. Finally in 1632 he published his masterpiece, Dialogue on the Two World Systems, in which—in the context of a hypothetical debate between three learned men—he ridiculed the Ptolemaic thesis. It was the arguments in this Dialogue that the Inquisition forced Galileo to recant one year later.

Galileo’s Philosophy of Science

Galileo was the first thinker to insist that at the heart of the opposition between science and traditional scholastic Aristotelianism was a distinction between numbers and words. As Galileo observed in the Assayer, Philosophy (science) is written in “mathematical language and its characters are triangles, circles and other geometrical figures.” Galileo rejected the insistence by Scholastics that science involved the constant reinterpretation of every newly discovered attribute of the physical world according to the explanations first offered by the ancient Greeks. For him, it had to be accepted that these new things could not be explained by the old teachings. In the Assayer he related the story of one of his Aristotelian colleagues who refused to look through his telescope for fear of seeing things he could not reconcile with his ideas, Galileo’s point being that it was only through such ignorance that old beliefs might be maintained. Yet Galileo did not propose to replace the old speculations with new ones. For him, science was not about what might be speculated and then justified; it was about what could be seen and then demonstrated. Like Francis Bacon, Galileo argued for an inductive method of investigation that built from observation to theory and then through experiment to validation of theory. But in a way that was different from Bacon, Galileo’s method required that those rationalizations be expressed in mathematics. If a scientific theory is true, he reasoned, it can be demonstrated mathematically; if it cannot be demonstrated mathematically, it is not true. It is from this perspective that Galileo sought to free science from the oversight of religious authorities. Science, he argued, was about the physical world and, as such, its proofs had nothing to do with religion. In a letter addressed to the Grand Duchess Christina of Tuscany, Galileo argued that it is wrong to use the Bible as a guide to the natural world. In seeking to condemn the Copernican thesis, he complained, his enemies cited passages in the Bible where it states that the sun moves, and the earth stands still. But it is wrong to take the Bible literally, he argued, because the words of the Bible have layers of meaning, and the literal, obvious layer is there essentially to keep the common people, who are “rude and unlearned” happy. According to Galileo, the Bible and Nature, “proceed alike from the Divine Word, the former as the dictate of the Holy Spirit, the latter as the obedient executrix of God’s commands.” God’s commands are the physical laws of the universe. Science, which could be defined as the effort to discover those laws, was thus only another form of Christian worship. Galileo argued, then, that the Copernican thesis was no challenge to the Bible’s authority because it reflected a truer understanding of God’s laws than did the traditional geocentric, or “earth-centered” theory. Its embrace signaled true Christian piety. But churchmen remained unmoved by Galileo’s arguments. Defenders of the Catholic Church have long pointed out that, at the time Galileo was writing, there was no definitive proof of the validity of the Copernican thesis, and that the experiments that Galileo thought granted such proof have since been proven faulty. The issue in Galileo’s censure, though, was not the quality of his science. The issue was whether or not an agency claiming moral authority, such as the Catholic Church, had the right to declare scientific investigation immoral. Galileo argued that it did not, but because he was a devout Catholic, he eventually acquiesced and submitted to the church’s condemnation of his argument. Those who followed him, however, saw him as a martyr for the truth.

Francis Bacon and the Rise of Experimental Science in England

Galileo’s fate actually compared favorably with that of the other individual responsible for making the case for science to early seventeenth-century audiences. After a life in its own way as illustrious as Galileo’s, Francis Bacon (1561-1626) found himself equally humiliated and condemned. Under James I of England, Bacon had a political career that saw him rise to the office of Lord Chancellor of England with a seat in the English House of Lords, only to lose it all after a conviction for taking bribes. Exiled from any association with the royal court in 1621, Bacon spent the last five years of his life studying science and philosophy and initiating vast writing projects he never completed. Bacon’s assault on scholastic Aristotelianism came from a different direction than that of Galileo. Both Bacon and Galileo followed the Italian philosopher Bernardino Telesio (1508-1588) in emphasizing that knowledge of nature, and therefore science, comes via sensory acquisition. Yet, while the five senses provided comparatively surer guides to the truth than the methods of intellectual conjecture preferred by the Scholastics, the senses are still prone to error. For Galileo, mathematical demonstration was the only fail-proof guide to the truth. For Bacon it was experimental demonstration. Bacon rejected an idea that would become the basis for the cognitive theories of his later countryman John Locke—the idea that the human mind is a “tabula rasa,” a blank page waiting to be filled with knowledge via sensory experience—and postulated that the human mind was prone toward four sorts of problems in its reception of data. Bacon labeled these sorts of problems “idols” to suggest, following the ancient Epicurean meaning of that term, factors that promote deception.

As Bacon put it, these idols created “enchanted” or “crooked” mirrors that change and pervert reality. The first of these, “Idols of the Tribe,” arose from features of human nature that clouded measured assessment of data, such as faulty or impaired senses or an instinct toward lumping versus one toward splitting. “Idols of the Cave” were the prejudices of individuals that obscured reasoned evaluation, such as a preference for one idea over another. “Idols of the Marketplace” had to do with the obstacles language places in the way of understanding. Here Bacon had in mind the fact that many of the qualitative terms that human beings use to describe phenomena in the physical world are, in fact, inadequate, incomplete, or overly general. Bacon cautioned against terms such as “moist” and “dry”—which were frequently used by natural philosophers of the period—for they lacked a precise character and therefore could not further scientific investigation. Bacon labeled the last sort of idols “Idols of the Theater” to denote the constructed, fictionalized character of intellectual theories. The pursuit of evidence to support theories, he argued, corrupted the evaluation of the results of experiments. Bacon advanced these arguments in his Novum Organum (New Organon; 1620), a work that has sometimes been called a “manifesto for the Scientific Revolution.” It set out his new method of inductive investigation as a way to minimize the impact of the idols he identified. As Bacon saw it, the old deductive method used by Aristotelian scholasticism throughout the Middle Ages and the Renaissance jumped from the identification of particulars to the formation of general principles, and only then built up the theories that linked the particular to the general. It completed all these steps without any empirical validation. The absence of independent verification meant that the idols he had identified literally shaped what was accepted as true. His new method insisted upon a slow ascent from particulars through theories that were independently validated through observation to general principles. Key to his method is the idea that knowledge is derived via trial and error; experiments that fail to produce or generate an independent theory, he argued, should be discarded. Theories that could not be proven false had to be accepted as true.

Bacon’s Idea of Progress

For most of the twentieth century, historians emphasized the degree to which Bacon’s inductive method had little to do with how scientists actually think. William Harvey, a contemporary of Bacon and the discoverer of the circulation of the blood, once quipped that Bacon pursued scientific research “like a Lord Chancellor,” meaning that like a government official Bacon sought to mandate scientific discoveries as opposed to accepting the leaps of imagination and deduction that so often lie behind scientific breakthroughs. Historians have built on this criticism, pointing out that a researcher following Bacon’s method would discover him/herself in an endless loop of validating only minutely different experiments, and more importantly that Bacon’s neglect of mathematics was a fatal flaw from which his method could not recover. More recent studies have sought to rehabilitate Bacon as a scientific forerunner, pointing out the inspiration, if not insight, he provided to many of the men who did participate in the Scientific Revolution. There is now also some appreciation of Bacon’s role in the creation of the empirical methods favored by social scientists, especially his arguments that experiments should be designed to disprove rather than prove a theory. While Bacon’s role in the actual production of science is the subject of debate and revision, his legacy as the first great advocate of science has always been acknowledged. It was Bacon who first made the case that knowledge is power and that the acquisition of knowledge enables states to become great. Significantly, what Bacon had in mind when he used the term “knowledge” was not “meta-physics,” that is, ideas that explain the hidden or unseen sources of life and the universe. It was instead “physics,” by which he had in mind a modern notion of nature and the technologies that can be used to exploit it. Bacon has also been correctly identified as the father of the “idea of progress,” the idea that life on earth can be made better through advancements in technology.

The Great Instauration

The literary character of Bacon’s writings allowed them to serve the scientific cause far more effectively than any piece of scientific research he did. In 1620 Bacon announced his plans to write a “Great Instauration,” a six-part proposal for the effective establishment of civilization on a scientific footing. Bacon only completed the first two parts of his proposal: The Advancement of Learning (1623) and the New Organon (1620). After Bacon’s untimely death in 1626, two of his other works were published together: the Sylva Sylvarum and the New Atlantis (1627). In the two parts of the Great Instauration he completed, Bacon presented his argument via a series of aphorisms, that is, pithy, witty, three-or four-sentence observations. The Sylva Sylvarum contained 100 “experiments,” actually conjectural explanations of various natural phenomena such as the cause of hiccups. The New Atlantis, perhaps the first piece of science fiction ever published, offered a utopian vision of a perfect society where, under the protective gaze of a wise ruler, a research institute called Solomon House continuously churned out inventions to make the lives of its citizens better. These four works were the most widely read of Bacon’s works. None of them provided any scientific information of merit, yet the absence of scientific content is what allowed them to be appropriated by generations of intellectuals seeking justification for programs of cultural reform. Thus in the 1660s the founders of the Royal Academy of Science in England saw themselves as realizing the ideas Bacon put forth in his New Atlantis, while in the eighteenth century, the editors of the French Enlightenment Encyclopédie signaled their identification with Bacon’s Great Instauration by placing his name on the first page of the first volume of their great work.

The Scientific Revolution and Philosophical Rationalism

Isaac Newton and the Confirmation of the Case for Science

Isaac Newton (1642-1727) was the first universally recognized scientific genius. In his Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), better known as the Principia (1687), he provided the mathematical demonstration necessary to prove his theory of gravity, and in doing so also lent irrefutable support to the Copernican thesis that the earth revolved around the sun. Beyond the Principia, Newton was also the discoverer (along with Gottfried Wilhelm Leibniz) of differential calculus, as well as the physical properties of light. He also invented the reflecting telescope. It was Newton who opened up the universe to scientific investigation by insisting that the physical laws that operate on Earth must also operate everywhere else, and that to discover what works on Earth is to discover what works in the universe. In making and announcing these discoveries Newton supplied the final push that turned European civilization toward the acceptance of science, not religion, as the basis of truth and knowledge. The contest between science and religion had been fiercely fought to a stalemate in the decades before Newton, with the defenders of religion, safe behind university walls, content to simply ignore the scientific challenge. The problem hindering the scientific assault was that advocates of science could not agree upon their own argument. The Copernican thesis was the cutting edge of the case being made for science, yet there was no consensus among the advocates of science that it was correct. Many of the arguments that Galileo advanced in favor of the thesis had been deeply flawed, and it is telling that Bacon chose to ignore the thesis in making his case for science. At the heart of the problem was an inability to explain scientifically the phenomenon that the accumulation of the data had revealed: the fact that the planets revolved around the sun in an elliptical rather than purely circular orbit. Newton’s theory of gravity solved these problems by advancing the notion that the sun’s pull on a planet was strongest when the planet was closest to it, and weakest when the planet was furthest away. His corollary development of the idea of centrifugal force—that at all times the pull of the sun on a planet was balanced by the pull of all other planets—definitively explained the phenomenon for which scientists had long been searching for an explanation. Newton’s theory forced even churchmen to accept the veracity of the Copernican thesis. As Alexander Pope observed in a famous couplet from his “Epitaph intended for Sir Isaac Newton,” “Nature and nature’s laws lay hid in night; God said “Let Newton be!” and all was light.” Contemporary Europeans embraced Newton—much as later twentieth-century Americans would celebrate Albert Einstein—as proof of the notion that through reasoned analysis it was possible to know nature, and, through nature, God. In his Lettres philosophiques (Philosophical Letters; 1734) Voltaire wrote with the aim of convincing Continental Europeans to follow the British cultural lead. Four of the twenty-four letters in the volume were devoted to explaining the work of Newton. Newton was a devout Christian who, it has been observed, wrote several million words of theology. Newton was also so deeply enamored of alchemy that the British economist John Maynard Keynes, who collected many of Newton’s alchemical works, once characterized Newton as “the last of the magicians.” Yet Voltaire correctly perceived that in the battle between science and religion, Newton was the ultimate weapon to defend science, and Voltaire passed on this awareness of the importance of Newton’s discoveries to other Enlightenment thinkers. While the editors of the French Enlightenment Encyclopédie may have pointed out their indebtedness to Francis Bacon for their inspiration, Newton’s new mechanistic universe was the justification for their work. His idea of a world held together by mathematical regularity, and by the opposing and counterbalancing forces of gravity and centrifugal force played a role in much of Enlightenment thought; this scientific model became, in other words, one of the dominant metaphors of the age, and its influence found its way into political theory, social criticism, and even the aesthetic writing of the period.

Optics and the Search for a Geometric God

It was not coincidental that Galileo built his case for the Copernican thesis on the evidence he derived from his telescopic observations, or that when Bacon wanted to convey the idea of the cognitive blinders that inhibit human comprehension he adopted the metaphor of distorting mirrors. The seventeenth century was captivated by optics and all technology that derived from the use of glass lenses, much in the same way that the modern world is obsessed with the possibilities that computers offer. Glass lenses, like modern computer chips, are made from silicon. In both instances it is not silicon itself, but the way it has been mathematically configured that creates its utility for humans. The important role that mathematics played in grinding the lenses that were used in telescopes and microscopes inspired numerous attempts at the time to unearth a “geometric God.” Seventeenth-century scientists still took as their departure point the premise that a supreme being had created the universe, and thus intellectuals thought that the geometric theorems that their technologies relied upon might be investigated to reveal the “secret” harmonies, proportions, and mathematical relationships God had used in His Creation. In this way geometry also became an important path of study for seventeenth-century philosophers, for, like scientists, they were convinced that it might reveal something about the attributes of the mind of God.

Rationalism and Mathematics

The chief exponents of the school of seventeenth-century philosophy known as rationalism were all in some way involved in the application of mathematical principles to technological problems. Both René Descartes (1596-1650) and Baruch Spinoza (1632-1677), the first two proponents of rationalism, had, in fact, made their living through lens grinding at one point or another in their careers. Rationalists like Descartes and Spinoza took as their starting point the notion that philosophy might follow a path to truth similar to that of mathematics, which derived its powerful theorems from axioms. In this way, rationalist philosophers became concerned with developing a way of working out the many logical implications of axiomatic statements concerning the nature of existence. To explain their method, one must first have a clear idea of how axioms and theorems function in mathematics. In geometry, for example, it is an axiom that a triangle is a two-dimensional figure or polygon composed by the intersection of three straight lines. All the theorems that have to do with different types of triangles follow from this axiom. In this sense, it can be said that these theorems are innate—that is, inherent in the axiom—and that it is the task of the mathematician to explicate them by logical deduction. Rationalists approached the study of God from this same perspective. Their goal was to demonstrate that God was the ultimate axiom from which all other axioms are logically derived. As a philosophical perspective, rationalism’s origins were ancient, and could be traced back to the ancient Greek mathematician Pythagoras, who noted the mathematical correspondences that occur in nature and concluded as a result that “all is number.” What was new in its reappearance in the seventeenth century was its application to the Christian intellectual tradition. To that point Christian thought took as a given that knowledge of God was revealed through the Bible or through visions and miracles. But rationalism rejected such revelation as a source of divine knowledge, and taught instead that true knowledge of God was innate within humans and could be deduced by the application of its rigorous intellectual method. Because they rejected the traditional role that divine revelation had long played in religious teaching, though, many rationalists were attacked as free thinkers and atheists.

René Descartes

The work of René Descartes has often been cited as the beginning of modern philosophy. At the time that Descartes began writing, skepticism had a pervasive influence over philosophical debate in Europe. Skepticism rejected the possibility of philosophical certainty. Its proponents argued that human beings were incapable of knowing truth and that they could only instead affirm through faith their own beliefs. Descartes sought to demonstrate that by following his rationalistic method, truth could be ascertained and known. His case for philosophical certainty was the starting point for every discussion of the topic during the Baroque and Enlightenment eras. Descartes was a first-rate mathematician, though his impact is mostly forgotten today. He pioneered the methods followed in analytic geometry, which has to do with the utilization of algebraic procedures to resolve geometric problems and vice-versa. It was Descartes also who introduced the practice still followed in algebra of assigning the letters a, b, c, etc., to known quantities, and the letters x, y, z, etc., to unknown quantities. Descartes’ religious sensibilities are the subject of some debate, and the stance taken in this debate dictates one’s interpretation of his work. One school of biographers has long emphasized the depths of Descartes’ Catholic faith, while another has charged that his display of religiosity was merely intended to ward off possible criticism. Untangling Descartes’ religious convictions remains a perilous enterprise. By upbringing, he was a Catholic, and he went to great lengths in his work to show that he was not of a similar mind to Galileo. When he learned that the Roman Church had condemned Galileo’s works, he even withdrew a manuscript from his publisher in which he had supported the Copernican thesis. Still other evidence of his insincerity must be admitted. Although a Catholic, for instance, Descartes chose to spend a large portion of his adult life living in Protestant Holland, where he was free to pursue his philosophical work without being forced to practice his religion. Yet Descartes presented his philosophy all the same as a scientific case for the existence of God. Those who see his faith as real appreciated his work as a heart-felt if unsuccessful effort to use mathematics to confirm religion. Those who see his faith as insincere have treated his work as a camouflaged expression of atheism. Whatever the position taken on his religious sensibilities, all commentators agree that Descartes was sincere in his belief that mathematics and the rationalism it might foster provided an antidote to philosophical skepticism, the teaching that ultimate truths could not be established. In his Discourse on Method (1637), Descartes mapped out his objections to existing philosophical approaches. In his Meditations on the First Philosophy: In Which the Existence of God and the Distinction Between Mind and Body are Demonstrated (1641), by far his most influential work, he built his case against philosophical skepticism. In this work Descartes presents his most famous argument against doubt in the immortal words “cogito ergo sum” or “I think, therefore I am.” For Descartes, when he used the word “cogito” (“I think”), he had in mind a “clear and distinct” idea whose truth was self-evident in the way the truth of a mathematical axiom is self-evident. Importantly, one ramification of Descartes’ notion was that it drew an absolute dichotomy between mind and body. Mind had to do exclusively with cognition, with thought. Body had nothing at all to do with thought. Thus, the mind could learn nothing of truth from the body, that is, through sensory perception and experience. The mind could only draw upon itself, upon the ideas that were innate within it. As a result the proof that Descartes fashioned for the existence of God stressed that since the human mind possessed an idea of perfection that idea must come from someone else. That someone else must be perfect, and since only God is perfect, He must have placed the idea of perfection in the human mind as proof of His existence.


Descartes’ ideas resonated among the intellectuals of his era, who were searching to find a way to prove God’s existence through a seemingly scientific and ironclad rationalistic approach. While many intellectuals agreed with his starting point, some took exception to the path he suggested. Of those, the most important figure to articulate an alternative path to Descartes’ rationalism was the Dutch Jewish thinker Baruch or Benedict Spinoza (1632-1677). Spinoza’s case against Descartes derived from two observations. First, Spinoza insisted that Descartes had not pushed his ideas to their logical conclusions, and that second, humankind’s spiritual freedom might be attained only if the logical conclusions of Descartes’ system were embraced. Descartes, it must be remembered, often backed away from public presentations of arguments that might result in his censure from orthodox forces. By contrast, Spinoza’s fate provides a powerful example of the consequences of making plain the theological implications that were inherent in a rationalist philosophical approach. As a young man Spinoza had been condemned and expelled from the Jewish community of Amsterdam. At this point he changed his name from Baruch to Benedict. Although a small group of thinkers recognized his achievements at the time of his death, for the most part Spinoza was reviled within the broader European intellectual community as an atheist. Modern commentators have emphasized that the characterization of Spinoza as an atheist is unfair. He had a strong faith in the Judeo-Christian deity; he just conceptualized that deity in a way that was distasteful to contemporary Jews and Christians. Key to Spinoza’s argument for the reality of God was his pantheism, an idea he developed in his Ethics, a work completed in 1675 but not published until after his death in 1677. Spinoza modeled the Ethics on the ancient Elements of Geometry of Euclid, and in it, he sought to demonstrate that all that exists in the universe is God. While Descartes had postulated a dichotomy between mind and body, Spinoza rejected that dichotomy and argued instead that mind and body are parallel expressions of the same thing. The human mind, in other words, has within it an impression of the tree that is physically before its eyes. The tree itself exists as an “extension,” a term that Descartes used to describe the physical and mathematical concreteness of things, but it exists all the same as a concept in the mind. In this sense mind and body are parts of the very same substance of which all existence is composed, and Spinoza identified that substance as God. In this way everything in the world is thus composed and contained within the deity.

The Controversy Over Spinoza

The tragedy for Spinoza was that this argument could be interpreted in various contradictory ways. It could be taken, for instance, as an affirmation of an immanent deity who might be worshipped through his attributes, or it could be interpreted as a rationale for an atheistic materialism. Since God exists in all things, in other words, Spinoza could be seen as reducing God’s importance to a superfluous detail. It was this latter interpretation of his work that dominated among the many contemporaries that attacked his ideas in the later seventeenth century. It has always been something of a puzzle as to why Spinoza was expelled from the Jewish community of Amsterdam so early in his life, but it remains plausible that perhaps this thinker’s early precocious arguments against a providential God and the immortality of the soul may have had something to do with his excommunication. For Spinoza, beliefs in God’s providence and the human soul’s immortality were only ideas designed to make the deity appealing to humans. They stood in the way of the appreciation of God’s human-dwarfing immensity, and it was only by appreciating this enormity that Spinoza believed humankind might find a path to spiritual freedom. In this regard his ideas concerning the human passions followed a similar logic. The passions made human beings and their affairs seem more important than they actually were when judged against the infinitude of God. Freeing oneself from the human passions was thus for Spinoza the only way to see God, and seeing God was the only way to ultimate freedom.

Gottfried Wilhelm Leibniz

The last contributor of new ideas to the rationalist school of philosophy was Leibniz (1646-1716). The son of a professor, Leibniz earned a law degree by the age of twenty. Somewhat later he began a career in the employ of German princes, primarily the dukes of Hanover, serving among other things as a librarian, a diplomat, an engineer, and an educational reformer. Along the way Leibniz gained fame for his mathematical genius. Historians grant the honor of the discovery of differential calculus to Isaac Newton, but recognize that Leibniz made the discovery independent of the former. Leibniz also sought to reconcile rationalism with German Protestantism. Descartes had postulated an opposition between mind and body. Leibniz dismissed this opposition by rejecting the notion that the body had some reality beyond the mind. He also argued that time and space, the substance in which the body was captured for Descartes, was illusory. Leibniz reversed the philosophical inclination to define being as static or passive existence. For him, to be was to do, doing being equated with thinking. He could thus treat mind and body as the active and passive, immaterial and material parts of a whole. The idea that matter was composed of atoms was just then beginning to take hold in scientific discourse. Since he rejected the idea that matter has any existence outside the mind, Leibniz developed as an alternative to the idea of the atom, the idea of the monad. The idea of monads can be discerned evolving in Leibniz’s work, reaching fruition in his Monadologia (Monadology; 1714), published two years before his death. Monads were the irreducible, indivisible, and metaphysical “things” that made up the world. As Leibniz characterized them, monads were complete concepts; they were self-contained and autonomous. Leibniz was extrapolating from mathematical reasoning here. What he had in mind was a sentence such as “A is equal to A,” a statement that would obviously remain true whatever the moment, whatever the situation. As Leibniz envisioned it, the set of valid predicates for each of these monads were some part immaterial, some part material in a hierarchical progression that stretched from the least active monads, such as those that took on the appearance of stone in the real world, to the most active, such as those that as a collectivity generated the appearance of the most sentient humans. The creator of all these monads was God, who remained the apex of the geometric pyramid favored by the rationalists, but who was now understood to be the monad for whom all other monads were predicates. Because he rejected the reality of material existence, Leibniz rejected the idea of causality, the idea that one thing in the material world caused another. Rather, he insisted that the predicates that exist for a given subject exist as a network of explanation from which it is possible to deduce the connection between events. For example, if one of the predicates for John is that he drives a car, and another of the predicates is that he is a careless driver, it is possible to deduce what Leibniz identified as the “sufficient reason” why John has a car accident. Applying this notion of sufficient reason to the world in which he lived, Leibniz argued that there was a rational explanation for all that occurred. It is in this sense that it is possible to extract from Leibniz’s ideas the notion that we live in “the best of all possible worlds,” the idea for which the French playwright Voltaire lampooned Leibniz in the figure of Doctor Pangloss, a central character in his satire Candide.

Nicholas Malebranche

Malebranche (1638-1715) was slightly senior in age to Leibniz, and his writings had their intellectual impact earlier than those of Leibniz. Like Leibniz, he was concerned with reconciling rationalism with Christianity, though in his case the Christianity in question was French Catholicism. He is often left out of discussions on Baroque philosophy because his contemporaries recognized him more as a disciple of Descartes than as the originator of new ideas. Yet in his role as a defender and reformer of the teachings of his master, he was perhaps the most influential of the rationalists after Descartes. Spinoza and Leibniz both used Descartes as the departure point for the development of their own systems of thought. Neither of these systems ever replaced that of Descartes as the definitive notion of rationalism. Malebranche rethought Descartes’ ideas in light of the criticisms that had been directed at them in the last part of the seventeenth century. In the eighteenth century, when rival philosophers talked about rationalism, what they inevitably had in mind was Descartes as amended by Malebranche. Male-branche’s life and career followed a pattern that recurred often in early-modern French intellectual life. Born with a deformed spine and a sickly constitution, he preferred a life of seclusion and scholarship early on. In 1664 he was ordained a priest, though he never took on any pastoral duties. In the same year, after failed efforts to become a historian, then a biblical scholar, he discovered the writings of Descartes. Descartes’ words caused his heart to “palpitate,” and he spent the rest of his life studying and explaining Descartes’ thoughts. Malebranche’s major work on Descartes, De la Recherche de la Verite (The Search After Truth) appeared in three volumes published in 1674 and 1675. In this work he advanced two ideas that shaped the understanding of Cartesianism. First was the notion of “vision in God,” the idea that all mental images or ideas exist only in God, and that at his discretion God allows man to see these things. Descartes had argued that ideas were innate within the human mind without working out how those ideas got there or how they were accessed on a moment-to-moment basis. For Descartes, it was sufficient to argue that God implanted ideas in the human mind at the moment of creation. Malebranche went beyond this and, fusing the ideas of Descartes with those of Saint Augustine, presented an image of an omnipresent God who continuously interacts with the human mind. Seemingly anticipating the assault on rationalist assumptions that was soon to come from empiricists, Malebranche rejected the argument that ideas came into the mind directly through the senses. The senses can reveal pain and pleasure. They cannot reveal what is causing pain or pleasure. Knowledge of what is outside the mind can only enter the mind through the representations placed there by God. What is perceived when one looks at a tree is not the tree as it really is, but the representation of the tree placed there by God. The second idea associated with Malebranche is “occasionalism,” the argument that God is the ultimate cause of every action. To get a sense of what Malebranche was striving to express here, think of a soccer game where in the closing minutes a player gives the ball a kick that sends the ball through the goal for a winning score. As Malebranche would explain it, the player in question would be the occasional or incidental cause of the winning kick. The real source of the kick was God, who used the player as an instrument of his will.


Pierre Bayle

Not every seventeenth-century intellectual engaged in scientific research embraced rationalism. Some rejected it as presuming to use mathematics to do something mathematics could not do, that is, validate the existence of God. Of these, the most important was Blaise Pascal (1623-1662), the French genius whose Jansenist convictions prompted him to affirm that God is only knowable through the insights he offers as gifts of grace to individual humans. Those trained in the traditional concerns of humanism, with its emphasis on creating a philosophy that might inspire virtue, similarly failed to concede the high road to the rationalists. Many thinkers who could be placed in this category adopted a skeptical posture that questioned the value of any knowledge of human affairs derived from scientific methods of reasoning. Of these, the most influential was Pierre Bayle (1647-1706). Bayle was born and raised as a French Huguenot, those that followed the teachings of John Calvin. For a brief period he converted to Catholicism, although his re-conversion to Calvinism necessitated his flight from France. Ultimately, he settled as a free man in Rotterdam, but he did so with the knowledge that the French government had imprisoned his brothers as punishment for his writings. They would eventually die in jail. Even in Rotterdam, clerical authorities attacked Bayle for the apparent atheism articulated in his writings. The trials and tribulations Bayle experienced because of his religious views made him a bitter opponent of any and all dogmas—proclamations of truth—whether they be religious, scientific, or otherwise. As Voltaire later characterized him with some hyperbole, Bayle had the finest mind for the “art of reasoning”—that is, critical analysis—of any intellectual “who ever wrote.” Bayle slowly examined any claim of truth and worked through its arguments to show the doubts about it every rational person had to recognize. One example of Bayle’s method was his discussion of “identity.” Since Descartes had based his proof of existence on consciousness, early-modern thinkers debated whether identity was continuous—whether a person has the same consciousness today that he or she had five days ago or five years ago. To a “learned theologian” who affirmed that consciousness is retained, Bayle posed the questions: “How do you know that, this morning, God did not let your soul fall back into nothing?” and “How do you know that God did not create another soul with the same modifications?” As Bayle concluded, “That new soul is the one you have now. Convince me to the contrary.” Bayle’s influence over philosophy stemmed from his Dictionnaire historique et critique (Historical and Critical Dictionary; 1702), a vast compendium of more than nine million words that was an international best-seller throughout much of eighteenth century. The articles in the dictionary were fairly straightforward. It was in his footnotes, though, that Bayle got into trouble. These were filled with the same relentless skepticism and questioning spirit that took no assumptions for granted that were found in all of Bayle’s writings. While he insisted that he was a believing Christian, he nevertheless compiled a significant body of works that were questioned, even in his own lifetime, as a challenge to his own religion. Recent scholarship may have become more supportive of the idea that Bayle’s confessions of faith were sincere, yet eighteenth-century philosophers who followed him were convinced of his questioning spirit and his use of human reason to undermine Christian teachings. Bayle’s work was particularly important for its impact on rationalistic arguments. His writings successfully assaulted the rationalists’ assumptions that mathematical reasoning could bring certainty to questions about human existence. In this way his work cleared the ground for the coming of empiricism, a school of philosophy that championed human observation and the insights it might offer.


By the second half of the seventeenth century, philosophical thinking in Europe had come to an impasse. Outside of clerical circles the traditional methods of university scholasticism had almost no appeal. Humanism, too, with its emphasis on ancient textual and literary study, was incapable of making sense of the ongoing discoveries that were occurring in science and beyond Europe’s boundaries in the journeys of exploration. Much of the new knowledge that was being amassed at the time, too, derived from new technologies like the telescope that extended the power of the human senses. For all these reasons, rationalism, with its rejection of the possibility of learning new things through the senses, left many people, but especially scientists, cold. In the works of Bayle can be seen some of the tensions of the age, and some scholars have long pointed to his work as a prime example of a resurgence of skepticism in the era. At the same time, the rapid rise of empiricism, a movement that, in fact, grew from Bayle’s very questioning cast of mind, cautions against an interpretation that points to a widespread resurgence of skepticism. It would be wrong to present the second half of the seventeenth century as waiting in anticipation of empiricism. Since modern philosophers continue to live in an intellectual universe where empiricist assumptions predominate and because they can look back and see this universe being born in the second half of the seventeenth century, it is useful to appreciate how empiricism fit with the European cultural sensibilities that were emerging in the seventeenth century in ways that no philosophical tradition has before, or since, been able to match. The key assumption of empiricism is the idea that knowledge comes through sensory experience. In contrast to rationalism’s affirmation of innate ideas, empiricism insists that a reality exists outside and beyond the human mind, and that it is through the senses that humans gain an understanding of this reality. Like rationalism, empiricism’s roots can be traced back to ancient Greek thought, specifically to the ideas of the Greek philosopher Epicurus (361-270 B.C.E.). Two of his conclusions were especially important to the later history of European empiricism. First, Epicurus recognized that the universe was made up of matter. From Democritus (460-370 B.C.E.) he derived a conception of the universe as a void or vacuum populated by atoms, which both figures understood to be irreducible, microscopic bits of matter. These atoms combined to create the macroscopic entities perceivable in the world. Epicurus added to Democritus the ideas that atoms have weight and thus naturally move in a downward direction, and that when atoms come together to form macroscopic entities, they coalesce in recognizable patterns that grant those entities discernible qualities such as the sweetness of honey or the whiteness of snow. It is worth stressing that the materialism implicit in Epicurus’ notion of the universe also proved attractive to later seventeenth-century European thinkers. But Epicurus rejected the existence of a spiritual world. As noted before, many commentators recognize Francis Bacon’s ideas as the source from which early-modern European scientists drew inspiration. This argument is true in the sense that Bacon’s ideas provided a rationalization of scientific investigation upon which both scientists and the public could agree. On the epistemological level, however—that is, the level of the theory of knowledge—it was Epicurus who provided scientists with direction. His materialism, though, was an obstacle to the reconciliation of his ideas with Christianity. Many of the charges of atheism leveled at early-modern scientists and philosophers can be traced back to their use of the ideas of Epicurus. The second idea of importance from Epicurus is that human understanding comes via the senses. The patterns in which atoms configured themselves grant them qualities discernible only through the five senses. Epicurus affirmed that the senses never lied. Any confusion concerning sensory input takes place in the human mind. Thus the way to knowledge is through using the senses to correct the mind.

Gassendi and Boyle

For most of the twentieth century scholars recognized John Locke as the initiator of the empiricist movement. Over the past few decades, however, the significance of the ideas of Pierre Gassendi (1592-1655) and Robert Boyle (1627-1691) as shapers of Locke’s thought has been increasingly appreciated. Gassendi suffered from physical infirmities like his contemporary Malebranche, and like Malebranche opted to enter the priesthood, though he never ministered a parish. Gassendi was the first person to record the orbital progression of a planet (Mercury), and thus provide evidence in support of Johannes Kepler’s laws of planetary motion. He was also the first scientist to identify and name the Aurora Borealis. It is perhaps revealing of the degree to which mathematics had taken over the debate concerning astronomy that in 1645, when Gassendi was honored for his achievements, he received a chair in mathematics at the College Royal of France. Gassendi was recognized as a scientist in his own day. History has remembered him, however, first and foremost as the individual who reintroduced Western civilization to the thought of Epicurus. Gassendi was one of the men invited to write comments on the first edition of Descartes’ Meditations. Gassendi took exception to Descartes’ appropriation of the methods of geometry and their application to the human quest for truth. For him, Descartes’ “cogito ergo sum” proved nothing. Rejecting Descartes’ claim that the pathway to truth traveled through the layers of the mind, Gassendi turned to the writings of Epicurus for proof that truth was something humans could only approximate. According to Gassendi, truth was reached through an inherently opposing process by which the senses acted against the mind to misinterpret the knowledge to which they were exposed. Gassendi believed in a “voluntarist” versus an “intellectualist” God, in other words, a God who does not just make laws but who actively shapes and reshapes those laws as he sees fit. From this perspective, Gassendi attacked Descartes’ argument that mathematical forms such as triangles are eternal. As Gassendi understood it, if triangles were eternal, they would then stand as something external to God and his creation, a possibility Gassendi totally rejected. Triangles, therefore, must be part of the world God created. And as Gassendi cautioned, “Don’t tell me if God destroyed it or established it otherwise, it would no longer be a Triangle.” From this direction, Gassendi saw the atoms of Epicurus as serving God’s command, and he sought to Christianize Epicurus, that is, to insert the Christian God as the animus or spirit in the materialistic universe that Epicurus had originally articulated. Thus whatever laws dictated the ways in which atoms came together, those laws had to be regarded as works in progress by God, who could and did, rework them over time according to his will. Gassendi’s ideas were eagerly embraced in England by Robert Boyle, best remembered as the discoverer of the law that bears his name that summarizes the relationship between pressure and the volume of gases. A point of contention among seventeenth-century scientists was whether the universe consisted of a vacuum—a void—or a plenum—a filled space. Seeking to avoid a stand on the issue, Boyle labeled the irreducible bits of matter that make up the world “corpuscles,” not atoms. But his corpuscles, like Gassendi’s atoms, were God’s building blocks. And while few people read Boyle for his corpuscular theory, the fact that Boyle explained his innumerable experiments based upon his corpuscular theory helped to diffuse his ideas among a broad readership.

John Locke

Among the young men who helped Boyle with his many experiments was an aspiring medical student named John Locke (1632-1704). Although his skills as a medic were what brought Locke to the attention of his eventual patron, Lord Shaftesbury, Locke spent very little of his adult life practicing medicine. Eventually, his medical research provided him with qualifications for entering into the Royal Academy of Science, but Locke spent most of his time engaged in politics. Shaftesbury was a leader of the Whig party, which for most of the 1680s stood in opposition to King Charles II and his brother, who eventually took the throne as James II. Having failed in his effort to have the English Parliament exclude James from the succession to the English throne, Shaftesbury escaped England for exile in Holland in 1682, where he died less than a year later. As a close associate of Shaftesbury, Locke also felt it prudent to follow him into exile, and he remained in Holland until the Glorious Revolution of 1688 forced James from the throne. During the 1680s, while he was on the run from agents of the English crown, Locke composed An Essay Concerning Human Understanding(1690), the source text from which modern philosophical empiricism developed. In the Epistle or “Letter” that Locke provided as a prologue to this work, Locke treated his philosophy as deriving from the “scientific” ideas of figures like Boyle and Newton, the “master builders” he argued that had left “lasting monuments” for “posterity.” His ideas were also shaped by the nature of the political-philosophical discourse that had occurred in England to this time. Although Thomas Hobbes’s Leviathan (1651) remained fresh in the memory of English readers in Locke’s day, this later philosopher came to far more optimistic conclusions than his predecessor had concerning the nature of humankind in a primitive state. His view of human psychology discarded the essential distrust and pessimism that had characterized Hobbes’s earlier work. Locke portrayed his own work as an “under-laborer,” inferior to the great achievements of Boyle and Newton. He was content, he wrote, to help “clear the ground” of some of the “rubbish that lies in the way of knowledge.” In making this statement Locke expressed a sensibility that remains alive in the modern social sciences: the idea that the methods of investigation and analysis developed in the study of nature can be less loftily but still usefully applied to the task of clearing up some of the confusion or “rubbish” concerning humans and their behavior.

Scope of Locke’s Essay

The Essay Concerning Human Understanding is divided into four books. In the first book, Locke runs through the arguments for the existence of innate ideas in order to disprove them; he calls attention to the fact that children are not born knowing the rules of logic. The second book of the Essay is the most important, for it is here that Locke presents the empiricist model of human cognition still embraced today. Locke argues that all knowledge comes through ideas, ideas being defined as the “objects” about which humans think. Introducing a metaphor still much in use, Locke pictured the human mind as a “blank page” that is filled through experience. There are two sorts of experience: “sensory,” involving the acquisition of knowledge from the outside world, and “reflective,” involving the manipulation within the mind of ideas already present. Likewise, there are two sorts of ideas: simple ideas having to do with the outside world that can only be received through the senses, and complex ideas that are the products of the mind’s treatment and refinement of simple ideas. While humans cannot know the “essence” of things, they can come to an approximate understanding of them. Through the senses, humans can gain an idea of the primary qualities of things—their shapes, their sizes—and also the secondary qualities of things—their smell, their taste, etc. Through reflection humans can then build complex notions about things humans can then test against further sensory experiences.

Berkeley and the Christianization of Empiricism

Although his ideas were sometimes perceived as an attack on the traditional Orthodox notion of the pervasiveness of Original Sin, Locke himself was a devout Christian who passed away while being read to from the Bible. Theologians attacked his Essay, but much of the venom of their criticism arose, not so much from Locke’s work, but from the way in which his ideas were being used. In 1696, John Toland (1670-1722) published his Christianity Not Mysterious. Toland based many of his observations on the empiricist arguments in Locke’s Essay, and used its reasoning to demonstrate that there was no validity at all in traditional revealed religion. Locke himself attempted to disown such a reading, but Edward Stillingfleet, the bishop of Worchester, argued after reading the Essay that it was a fair extrapolation. In a series of letters published between 1696 and 1702, Locke and Stillingfleet engaged in a polemic over whether the Essay undermined Christian faith. The point of contention was the distinction Locke insisted existed between knowledge, for which the criterion of truth had to be certainty, and faith, which by definition for Locke could only be accepted as probable. The demarcation of knowledge as something that could be only understood as true or untrue was the innovation for which Locke was being challenged. Locke was separating the understanding of the natural world and its societies from the understanding of God. As a result, he argued that the understanding of the world could be arrived at only by following empiricist procedures, while the understanding of God could never be arrived at with certainty following empiricist procedures. It was exactly upon this last point that George Berkeley (1685-1753), Anglican bishop of Cloyne in Ireland, also challenged Locke. Following Gassendi’s reading of Epicurus, Locke had granted the material world a charter of independence from the spiritual world. The material world, Locke argued, could only be approached from a materialist perspective, an argument Berkeley rejected. Instead Berkeley denied the existence of a material world altogether, and denied the existence of any concrete realities outside the mind that human beings might attain some level of certainty in understanding. Whatever was out there existed solely as ideas and nothing more as they were brought within the compass of human understanding. Berkeley modified Descartes’ “Cogito ergo sum” (“I think, therefore I am”) to read, “Esse est percipi” (“to be is to perceive”), his point being that the one certainty humans can have is that the act of being empirical—the act of receiving information through the senses—is the validation of their conscious existence. Berkeley was a man of considerable intellectual powers. He had sufficient command of mathematics, in fact, to expose errors in Newton’s calculus. It is thus significant that he turned away from science and back toward religion. His career both before and after his appointment as bishop of Cloyne can be characterized by his concern to stop what he took to be the erosion of collective belief. He identified philosophical materialism as the source of that erosion, and sought to make the case against its integrity. Berkeley’s empiricism thus represented a break with the empiricism of his predecessors in that instead of attempting to free the scientific study of the physical universe from the oversight of theologians, he sought to demonstrate that whatever insights scientists gleaned about the physical universe were gifts from God. They were, in other words, signs of God’s benevolence similar to the gifts the divinity had also given humankind through his revelation. In his youthful writings Berkeley had emphasized that insights about the physical universe came through the senses; now in his latter works, he articulated a Neo-Platonic position that allowed for some ideas to be innate in the human mind. Berkeley’s efforts at Christianizing empiricism thus ended with a negation of the empiricist elements in his philosophy.

Condillac and Sensationism

British empiricism had a powerful impact on intellectual thought everywhere in eighteenth-century Europe, but only one thinker on the continent made an original contribution to the empiricist school of thought. In 1688, William Molyneux, secretary to the Royal Irish Academy, sent a philosophical problem to John Locke that Molyneux hoped Locke would try his hand in solving. Suppose, Molyneux’s problem began, a man born blind was trained to recognize a sphere and a cube by touch. Suppose then that this individual was granted sight. Would the individual then be able to identify a sphere and a cube by sight correctly without touching them? Locke concluded that the answer was “No.” Later, when he took up the same problem, Berkeley reached the same conclusion. Both men saw this problem as turning on the issue of depth perception, and concluded, albeit with different justifications, that the circle and square that would confront the untrained eye would not immediately be recognized as a sphere and cube. Depth perception was not innate. The French empiricist Étienne Bonnot de Condillac (1714-1780), writing after Locke and Berkeley, suggested that Molyneux’s problem was not about depth perception, but about the connections between the senses and the mind, and that Locke and Berkeley did not go far enough in their conclusions. To Condillac’s mind, the question of depth perception took for granted that the mind was aware that there is a world outside the body where there are some things that are closer and some things that are further away. How did the mind, Condillac pondered, first come to realize that a world existed outside itself? Like Malebranche and Gassendi, Condillac was a sickly child who turned to scholarship and then to the priesthood. Condillac lived a much more varied life than either of these men, however. As a young man, he was part of an intellectual circle that included Jean-Jacques Rousseau and Denis Diderot. And for ten years of his life he served as the private tutor of the duke of Parma, the grandson of Louis XV (r. 1715-1774). Condillac’s brand of empiricism has been labeled “sensationism.” Sensationism moved beyond other forms of empiricism in insisting that all attributes of consciousness are the products of the senses. Whereas Locke’s idea of empiricism maintained that ideas were derived from experiences, it took for granted that the mental processes through which experiences were turned into ideas were themselves innate. Condillac argued, by contrast, that mental processes were themselves the results of experience. In his Treatise on Sensations (1754) Condillac went Molyneux one better and asked his readers to imagine what would happen if an inanimate statue came to consciousness, acquiring the five senses either in isolation or in various sequences. As Condillac saw it, the consciousness of the statue—that is, what it would know itself to be—would be a function of the combination of senses available to it. Condillac saw the human mind as passive and immobile. All it could do was react to the sensations, the impulses of data that flowed into it from the senses. Gradually, it learned to manipulate the data, to compare and contrast the latter, to arrange the latter in patterns, these acts signaling the acquisition of the mental processes earlier empiricists took as innate. As for the question of how the human mind first realized that a world existed outside itself, according to Condillac that discovery was a product of the sense of touch. Only after a human has touched an external object is it brought home to the mind that something exists that is not an extension of it.

Hume and the Secularization of Empiricism

Meanwhile, back in Britain, Condillac’s contemporary David Hume (1711-1776) was pushing empiricism in yet another direction. Like Locke, Hume was a thinker whose ideas have continued to influence the discussion of a number of topics. In the twentieth century Hume was celebrated by the philosophical naturalists, thinkers who argued that while science does not supply all the answers, its methods of investigation remain the best starting point for deriving answers. They recognized Hume as their distant forebear, an identification for which there is some justification. Hume saw himself as applying the “experimental method of reasoning” demonstrated by Newton to the “science of human nature.” At the same time he has been seen as an important force that kept alive philosophical skepticism. Just as Hume reinforced the dichotomy Locke postulated between knowledge of the material world and belief in God, so Hume used Bayle’s skepticism as a scalpel to slice away at the arguments through which the discussion of the physical universe had long been kept within a Christian intellectual framework. Whether Hume saw skepticism as an end in itself or merely as a tool to clear the way for his scientific philosophy remains an open question. Hume, though, more than any other figure in the empiricist movement, led the charge to secularize, that is, strip away the religious dimension from Europe’s philosophical discourse. While he took up this mission in almost all his writings, the subject of all his thinking can be gleaned in his Treatise on Human Nature (1739-1740). Hume complained about the lack of public approval his treatise generated, remembering it later as having “fell dead-born from the press.” So he spent the rest of his career re-packaging the ideas in the Treatise, and nowhere did he do so more effectively than in his Enquiry Concerning Human Understanding (1748). Hume recognized the twofold distinction that Locke had argued existed between sensory inputs and the mental representations they triggered. Hume labeled the former “impressions,” the latter “ideas.” Hume’s first insight is that ideas are only “copies” of impressions. His second insight is what has been called his “liveliness” thesis: the notion that what separates ideas from impressions is the vividness of the copies. To use a modern analogy, if an image is photocopied, and then the photocopy is photocopied, each successive image will have less and less of the detail of the original. The difficulty with understanding Hume often resulted from his attacking and dismissing the “useless” ideas that he was trying to replace with his own theories. His attacks on traditional received wisdom, in other words, can be so vitriolic and entertaining that they sometimes cloud over what he had to say that was new. Using his two insights, Hume argued that all knowledge should be scrutinized to determine its factual versus its fictional character. The question concerning every idea that must be asked is “from what impression did it derive.” If the source of the impression cannot be determined, Hume contends, it has no empirical validity. Hume skewered ideas concerning faith, miracles, and the supernatural because they possessed no empirical validation. Having dismissed the possibility of any spiritual basis for morality, Hume sought to establish an Epicurean notion of human ethical conduct: the pursuit of pleasure versus the avoidance of pain should be, he argued, the yardstick against which all human actions are judged. In this way, he helped to set the stage for philosophical utilitarianism in the nineteenth century.

The Enlightenment

The Big Picture

The Enlightenment was a broad and international movement in eighteenth-century Europe that aimed at placing science and knowledge derived through scientific methods of investigation at the heart of culture and civilization. It took its name from the idea that it represented: a process of bringing “the light of reason” to areas of darkness in human understanding. “Dare to know” was the banner call of the movement proclaimed by the German philosopher Immanuel Kant (1724-1804). Contemporaries understood this call as an invitation to hunt down and root out every instance of ignorance that continued to stand in the way of human progress. In many instances, certainly in most Catholic lands, religion in general and the state church in particular were identified as the prime sources of such ignorance. As such, the Enlightenment often took on a definite anti-religious cast in these regions. In terms of real people and real events this means that the Enlightenment can be seen as the sum of a series of organized efforts on the part of secular intellectuals to institute their ideas, usually as alternatives to those of the church. The Enlightenment was historically important in large part because these efforts proved to be successful over the long term. Enlightenment ideas, and the secular intellectuals who promoted these ideas, triumphed over existing social and cultural notions, most of which had long been dominated by traditional Christian orthodoxy. And while the idea that there was a positive value to cultural reforms based on science has not gone unchallenged in the modern era, those notions, born in the Enlightenment, have continued to be dominant in the West until contemporary times.

For Good or for Evil

Such a description of the Enlightenment, though, presents only the few points on which there is broad agreement among scholars. Everything else about the culture and philosophy of the movement has continued to remain disputed. In recent decades, the most agitated of these debates has been over the question of the social and cultural costs of the Enlightenment. Inspired primarily by the writings of the French thinker Michel Foucault (1926-1984), some scholars have argued that the Enlightenment simply substituted one sort of darkness with another. Science, they argue, became a justification for racism, sexism, and an entire host of other kinds of exploitation, just like religion had before it. Such criticism has not gone unchallenged, and others have countered that scientific investigation has, in fact, been a force for progress. While these figures readily admit that bad science has often been a dehumanizing force in the West, they have pointed out that its relentless pursuit of correct knowledge has been an overall positive force in the European tradition. Another debate, a debate that grew up in the Enlightenment itself, has also touched upon the moral consequences and costs of the movement itself. Critics approaching this problem from a religious perspective have pointed to the Enlightenment as the source for the rise of “secular humanism” and a moral relativism that it inspired. Champions of Enlightenment values, on the other hand, have pointed to Western society’s traditionally repressive and intolerant nature before the eighteenth century. In this view, the Enlightenment has been seen as a force that helped to bring to an end centuries of religious hypocrisy in which only lip service had been paid to moral values. The Enlightenment may have fostered a moral relativism, they conclude, but it also allowed societies to recognize that humans are by nature different, and that they can be made to seem the same only through coercion.

Public Opinion

In recent years scholars have pushed their investigations of the origins of the Enlightenment backwards into the seventeenth century. They have begun to speak of the ideas of intellectuals like John Locke as the first wave of enlightened thought. The motivation behind this tendency is a desire to associate the Enlightenment with the development of empiricism. This desire has been prompted in large part by another trend of scholarship on the Enlightenment itself: a tendency to interpret that movement as an international phenomenon that followed very distinct paths in Europe’s individual states. In this regard, the French Enlightenment has now been revealed to have been very different from its German and English cousins. But if the Enlightenment was different everywhere, then what can be said about it as a general historical phenomenon? When the Enlightenment is viewed as an outgrowth of empiricism, its common features become more obvious, although there is no direct and simple equation between empiricism and the later development of Enlightenment. While it is true that many Enlightenment thinkers were empiricists, and that empiricism was the philosophical foundation for most of the new intellectual disciplines that emerged during the Enlightenment, it is also true that the thoughts of many of the movement’s thinkers deny easy categorization as “empirical.” One of the links between these figures, though, was their willingness to affirm the existence of something that modern scholars call “public opinion,” and their tendency to appeal to this new social arena of judgment for justification for the various sorts of reforms they advocated. Everywhere in eighteenth-century Europe, social reformers framed their ideas by reference to public welfare or the common good, even as they branded those that opposed their ideas as “special interests” that were corrupt, intolerant, and fanatical. This common development is the best starting point for a discussion of the Enlightenment as a general phenomenon.

The Reading Revolution

Behind the birth of “public opinion” was another cultural and social revolution that must be understood, a “reading revolution” that created new groups of readers and writers. In medieval Europe the “Republic of Letters”—the body of those that had used the written word to circulate their ideas—had an undeniably clerical cast. In the Renaissance, more and more lay people had acquired the ability to read and write, and they had begun communicating their ideas through the printed page. By the eighteenth century the vast majority of readers and writers were now lay people rather than clerics. This steady expansion in the number of society’s readers inspired new genres of reading material, even as it also created new modes by which information and news spread in society. The eighteenth-century reading public was now vast, but also complex and differentiated along lines of social class, education, and taste. To entertain and inform these various groups of readers, older types of printed communications, like the news broadsheet or the polemical pamphlet, now underwent a steady evolution, while at the same time new forms of reading matter, like the newspaper and the journal, developed. To supply the articles, stories, and thought pieces that went into these publications, a new occupation—that of the professional writer or “man of letters”—emerged. From individuals who made their living writing and publishing their own local newspaper, to internationally famous writers whose books were immediately translated into other languages, these individuals all made their living by saying in print what this new group of readers wanted to hear.

The Coffeehouse

In the largest sense, these new groups of readers constituted the public opinion to which Enlightenment thinkers appealed, but much eighteenth-century writing was geared, not to all readers generally, but to a new category of bourgeois readers, in particular. This class became a common fixture of the economic landscape in most European countries around 1700. By this date, rising economic prosperity had forged a new middle class that often lived off the interest that their investments provided. With plenty of free time on their hands, members of this group spent their days in a new type of commercial establishment, the café or coffeehouse. There they sipped cups of the new beverages, coffee and tea, which were sweetened by sugar, the new wonder condiment, and smoked pipes filled with “sot weed” or tobacco. These new venues had begun to appear in London in the years around 1650, and within two generations they had spread to most European cities. In English, they were often called “penny universities,” because for a mere penny men could be admitted into a society where others shared their concerns. For this modest cost of admission, men were able to read from an assortment of books, newspapers, and journals coffee-houses made available to their patrons. The idea of leisure time reading is key here because it helps explain the second social development that amplified the impact of Enlightenment thought. In the eighteenth century talking became a pastime in many of the ways it remains today. Enlightenment-era thinkers were conscious of themselves as having come up with not just new ideas, but new ways of communicating those ideas. The “art” of conversation—conversation that connoted the exchange of information via polite discourse—was the subject of essays and discussions. The concern was to find ways to move beyond the social hierarchy that had constrained oral communication in the past. The ideal was to create situations where individuals, no matter their social rank, could exchange ideas as intellectual equals. In the twenty-first century both radio and television offer a myriad of talk shows aimed at informing the public of news and ideas while also providing their listeners with a particular “spin” on news and ideas. The origins of this incessant commentary stretch back to the eighteenth-century Enlightenment world of the coffee-house. In that world the art of conversation was practiced, and leisure reading provided a steady inspiration for the enrichment of discussion. In this way, the goal of much of the writing that appeared in the Enlightenment was to elicit conversation. The letter of one frustrated exile from the Paris salons to a friend voiced a sentiment shared by all those who were participating in the new world of the Enlightenment: “Reading alone, with no one to talk to, to discuss things with or be witty with, to listen to or to listen to me, is impossible.” Enlightenment thinkers framed what they had to say in ways they hoped would get people talking, and the measure of success of a piece of writing was its power as a conversation starter. Many of the men whose ideas inspired the coffeehouse chatter of the eighteenth century may not have spent much time themselves in the new cafés, but their eminence as “great” writers derived in large part because their works became the subject of the new kinds of debate that the Enlightenment helped to sanction. And while “public opinion” did not reside solely in the coffeehouse, it still constituted an important element of the audiences that Enlightenment thinkers hoped to influence.

The Enlightenment in France

The Role of Paris

Paris was the home of the Enlightenment, and most discussions of the Enlightenment are actually discussions of its unfolding there. The French Enlightenment was characterized by the emergence of a group of thinkers, the philosophes, whose writings sought to give the Enlightenment everywhere both a rationale and an agenda. These philosophes met regularly in the afternoons at the homes of well-heeled patrons, where they would discuss events and ideas over elegant meals. These salons were the envy of European intellectual circles. The defining achievement of the French Enlightenment was the publication of the Encyclopédie, a multi-volume compendium of all useful knowledge that was to kick-start European civilization in the direction of progress. The philosophes were “men of letters,” which, as Voltaire explained, meant that they were not scholars but explorers of all knowledge. This idea helps explain why so few of the philosophes offered original contributions to philosophy. Their ambition was not to come up with anything new in the way of ideas, but to put what was known to work in ways helpful to humankind. The archetype of the philosophe was Voltaire, who with some success tried his hand at almost every genre of writing. Philosophically, Voltaire had little to say, but he did perform an important service for the Enlightenment through his efforts to introduce Continental intellectuals to English institutions and ideas. Exiled from Paris, Voltaire spent the years between 1726 and 1729 in London where he studied the writings of John Locke and attended the funeral of Isaac Newton. Later, Voltaire published a series of essays in the forms of letters, the Letters on the English, or, as it is also called, the Philosophical Letters (1734). These made the case that governments and societies on the Continent should imitate English examples. Still later, Voltaire wrote a study of the ideas of Newton and together with his mistress, Madame de Chatelet, he published a French translation of Newton’s Principia. Because of his penchant for insulting powerful people, Voltaire actually spent very little of his adult life in Paris, and thus he partook little of the city’s salon life. There were several different levels of these weekly dinner parties, almost all directed by women. But at the height of the Enlightenment during the 1760s four salons sat atop the social and intellectual pyramid in the city: two run by men and two by women. On Mondays, Madame Geoffrin invited artists to her home to dine, while on Wednesdays she entertained writers. Tuesdays belonged to the philosophe Claude Adrien Helvetius (1715-1771). Thursdays and Sundays were the occasions for the salons held by another philosophe, the Baron D’Holbach (1723-1789), while Fridays were the days set aside for dinner at Madame Neckar’s. Very few great intellectual moments may have taken place at these salons, but they did much to glamorize and romanticize the lives of intellectuals.

The Encyclopédie

The men who wrote the Encyclopédie often congregated at Madame Geoffrin’s house. This great project to summarize all science and wisdom in a single set of volumes was perhaps the greatest intellectual achievement of the French Enlightenment. Encyclopedic compendiums were certainly not new in the eighteenth century. Pierre Bayle’s massive critical dictionary from around 1700, with its nine million words of text, had been just one of the many works that inspired the great French project that began in 1751. Originally, this new Encyclopédie had begun merely as a work to translate the Cyclopedia, or an Universal Dictionary of Arts and Sciences (1728) by Ephraim Chambers. Eventually, the two editors of the French project, though, discarded the idea of a mere translation and began a massive work of compilation. What made the Encyclopédie a clear standout among the many such compendia published in the seventeenth and eighteenth centuries was that it was not written by experts, but by the philosophes. Eventually, the finished product totaled 28 volumes, as well as several supplements. Although such a large work did not present a single point of view, the editors Denis Diderot and Jean d’Alembert often chose like-minded intellectuals, and thus the tone of much of the writing was often distinctly anti-clerical and anti-religious, even as the text advocated reforms along the lines such Enlighteners favored. The text, too, was not aimed at a specialist, but a generalist reader, and thus it had a great impact in fashioning taste in later eighteenth-century Europe. The ultimate message of the project, though, was that which Francis Bacon had first expressed: human life could be made better through knowledge. By 1789, some 25,000 sets were in circulation across Europe, and the Encyclopédie had become one of the Enlightenment’s great publishing success stories.

Jean-Jacques Rousseau

Of the many individuals who wrote during the French Enlightenment, one man stands out for the originality and force of his ideas. The work of Jean-Jacques Rousseau (1712-1778) defies compartmentalization. There is some debate among scholars in fact over the question of whether he should be considered an exponent of the Enlightenment or a harbinger of the Romantic Age that followed it. Rousseau himself was a deeply enigmatic figure, one that seemed to march to a different drumbeat set by demons. The one thing known about his early life is that he was born in Geneva. The rest of the information about his youth has to culled from his autobiographical Confessions (1782-1789), written just before he died, which paints a Romantic picture of a young roustabout introduced to life, learning, and love by an older woman.

What is known for certain is that in 1742 Rousseau arrived in Paris hoping to make a name for himself as a musical theorist. He quickly became a friend of Denis Diderot and the circle of men writing the Encyclopédie; Rousseau wrote most of the articles in that work having to do with music. The first flashes of Rousseau’s brilliance came in his debate with Jean-Philippe Rameau, the most powerful authority on music in France. The official topic of the debate was the relative merits of French versus Italian opera; below the surface the subject was really the superiority of rationality to emotion. In the context of this debate Rousseau put forward the idea that artistic creativity should take precedence over the forms in which it is expressed. In 1750 Rousseau won first prize in an essay contest sponsored by the Academy of Dijon for his Discourse on the Sciences and the Arts, in which he made the case that civilization has a corrupting influence on humankind. In 1755 Rousseau submitted another essay to the competition sponsored by the same academy, and his Discourse on the Origins of Inequality also won first prize. More importantly, it established him as a philosopher of merit. Taking up where the earlier essay had left off, this second Discourse argued for the existence of two types of inequality: natural inequality, which has to do with the fact that one man is stronger or smarter than another, and artificial inequality, which was the inequality imposed between individuals by society. As Rousseau explained it, man in the state of nature was solitary but happy. The need to procreate turned the solitary individual toward village life and prompted the evolution toward civilization. Each step forward in the evolution of society, however, alienated the solitary individual from himself, the crucial step being the invention of private property, which triggered the development of law and government to protect the claims of owners, a development that ensured the continuation of artificial inequality over generations. “Man is born free, but everywhere he is in chains” is actually the opening line to The Social Contract (1762), the book Rousseau wrote to prescribe the way out of the situation described in The Discourse on the Origins of Inequality. As he outlined there, society must make explicit the pact or social contract that is implicit in communal living to find a way to salvation. Each society, each community has to be looked upon in the same way that an individual is examined—as the articulator of a specific will. To the extent to which the members of a society can shape and share that will, then those members will come to know liberty because they will have control over their own destinies.

The Enlightenment Elsewhere in Europe


The English and Scottish Enlightenments might be looked upon as complementary halves of a whole. English thinkers supplied very little philosophical importance to the Enlightenment, being mostly concerned with the development and application of technological and scientific ideas. Scottish thinkers, by contrast, made some of the most original and lasting contributions to philosophy in the eighteenth century. Unlike France, where the philosophes developed Paris into a center of literary ferment and glittering social life, the Enlightenment in England had no center, produced very little literature of note, and spawned a very different social venue for the exchange of ideas. Through their written works, the French Enlighteners hoped to encourage their country’s government to adopt social reforms. In England, by contrast, Enlightenment thought concentrated on what could be done in the private sector to bring about progress. In France the Enlightenment was in the hands of “men of letters.” In England it was businessmen, industrialists and agricultural entrepreneurs who saw themselves as leading the charge toward the future. Significantly, English thinkers were always in the hunt for new things, “new things” being understood to mean innovations whose value could be measured by their impact on the profit margin, and the commercial cast of much eighteenth-century English political and social writing is undeniable when compared against the French philosophes. The one gathering that might pass as a salon in England was the Literary Club that the painter Joshua Reynolds organized in the 1760s in London around his friend Samuel Johnson. Otherwise, those interested in discussing progress and the future came together in scientific associations and literary and philosophical societies. These met on a weekly basis, with a lecture or demonstration serving as the starting point for conversation. The best known of the English associations was the Lunar Society of Birmingham, founded by the industrialist Matthew Boulton (1728-1809), famous then for the success of his tool and die factory but better known in history for supplying the capital that allowed James Watt to develop the steam engine. The Lunar Society met only on nights when the moon was full, so that there would be sufficient light for members to make their way home.


In France and England, the Enlightenment did not have much connection with the universities. In both states the universities remained the territory of the clergy, the group of thinkers most antithetical to Enlightenment thought. This was not the case in Scotland where, with the notable exception of David Hume (1711-1776) who was suspected of being an atheist, most of the leading thinkers of the Scottish Enlightenment held positions in the university. Glasgow was the university most open to Enlightenment thought. Adam Smith (1723-1790), the great eighteenth-century economic theorist, held a chair in Moral Philosophy there. Smith’s tenure was followed by Thomas Reid (1710-1796), founder of the “Common Sense” school of Scottish philosophy, which challenged the skepticism of Hume. They argued that what humans need to know is obvious to them as common sense. Another Enlightenment figure that taught at Glasgow was the chemist Joseph Black (1728-1799), famous for first identifying the properties of carbon dioxide. During the 1780s, Edinburgh began to replace Glasgow as a center of Enlightenment thinking, especially after the founding of the Royal Society of Edinburgh in 1783. Much like the scientific societies in England, the Royal Society provided a venue in which visiting speakers could lecture and discuss their ideas with members. In this way, the society brought the culture of the Enlightenment in Scotland into alignment with that in England.

The Enlightenment in Germany

In both France and Britain the Enlightenment took place outside of government circles. In Germanic lands, by contrast, the Aufklärung, as the Enlightenment was known, became a reform movement that was, in fact, sponsored and directed by rulers. The reformist ideas of the French philosophes were not taken all that seriously by the government at Versailles, but in royal palaces in Berlin and Vienna, the capitals respectively of the kingdoms of Prussia and Austria, these ideas became the basis for the first serious efforts at social reform. In Berlin the Enlightenment occasioned a great outpouring of writings on culture and religion by German intellectuals. Immanuel Kant (1724-1804), whose impact on philosophy was not equaled by any of his contemporaries, was a product of the Prussian Enlightenment. Still the Enlightenment in the Holy Roman Empire was made most vividly evident to ordinary Germans through the efforts of territorial rulers to modernize their societies through the application of ideas that emerged in France. The idea that the Enlightenment should be implemented from the top downward was the first and most important French idea embraced by the Germans. Voltaire had argued for it, and wrote a history of Louis XIV entitled Le siécle de Louis XIV (The Century of Louis XIV; 1751) to demonstrate the glory that might be acquired by a ruler who took the initiative to reform his realm. The notion first attracted an audience in Potsdam, where the summer palace of Frederick the Great, king of Prussia, was located. Frederick tried to expose the Prussian ruling class to the new ideas that were developing in France. In 1744, he revived the Berlin Academy of Science, which had been established by Gottfried Wilhelm Leibniz in 1700, but which had fallen into neglect. At the suggestion of Voltaire, Frederick invited the French mathematician Pierre-Louis Moreau de Maupertuis (1698-1759) to serve as president of the Academy, and when Maupertuis stepped down, Frederick unsuccessfully sought to have Jean d’Alembert, one of the two original editors of the Encyclopédie, take the position. During Frederick’s reign the publications of the Academy were all in French, but as an institution it still opened doors for German intellectuals. The most striking example of its fulfillment of this function came in 1763 when the Jewish intellectual Moses Mendelssohn won an Academy-sponsored essay contest on the nature of metaphysics. Frederick the Great was the first and greatest example of what historians have labeled an “enlightened despot,” meaning a ruler who exercised absolute control over his state but who used this authority with a mind to improving the lives of his subjects. Perhaps the best illustrations of these instincts were Frederick’s decree establishing religious toleration in his lands and his reforms of the Prussian judicial system. The second great eighteenth-century ruler to sponsor similar reforms was Joseph II of Austria (1741-1790), the eldest son of the empress Maria Theresa. He ruled with his mother from 1765 to 1780, and by himself from 1780 to 1790. Unlike Frederick the Great, Joseph imported French ideas, but he did not bother to bring French philosophes to his court. His most important reforms involved the state’s relationships with the Catholic Church. He closed many monasteries and turned their revenues toward the founding of hospitals and other social welfare institutions. He sought to reform education also, on the one hand freeing the University of Vienna from clerical control, and on the other establishing a system of state-maintained seminaries for the training of priests. He granted freedom of worship to Protestants and Jews, and attempted to free the serfs. Although his ambitions for Austria were great, his enlightened reforms led to revolts across Austria and Hungary, and Joseph died a broken man.

Immanuel Kant

The greatest philosopher of the German Enlightenment was undoubtedly Immanuel Kant (1724-1804), a thinker whose ideas have long puzzled and perplexed his readers but who made a major contribution to the emergence of psychology as a discipline in the modern world. As a philosopher living in the early-modern era, Kant treated many issues that are now the preserve of psychologists. The topics that early-modern philosophers often treated—particularly their return over and over again to the subject of human epistemology and cognition—have now been explained scientifically, that is by cognitive research that has been validated by a stream of experiments. Early-modern philosophers lacked the ability to perform such tests, but even more importantly, they lacked the mindset that would seek to adjudicate a dispute by reference to quantitative data. They thought of explaining thinking only in terms of the logical analysis of thought. Or, to put the point in the terms that Kant would put it, they attempted to use a tool—in this case, the human mind—to explain the functioning of that tool. What made the work of Kant so important for the future was his insistence that instead of allowing the constraints to the operation of human consciousness to serve as obstacles to an understanding of such consciousness, it is better to identify those constraints and to seek to determine how they shape human consciousness. In this way Kant reconciled the major differences between rationalism and empiricism, and moved philosophical discussion to a new stage. Kant was the greatest Enlightenment figure to go against the grain of the ideals set down by the French philosophes. He was born in the Prussian city of Königsberg, and over the course of his eighty years never traveled more than sixty miles from it. He was reputedly so punctual in his habits that the town clock was set according to his daily routine. After many years of working as a private tutor for noble families, Kant was awarded a professorship at the University of Königsberg only in 1771. There he completed his most important work, including his Critique of Pure Reason (1781). In the text Kant shows how the dialectical opposition posed by the rationalists and empiricists could be resolved through a new synthesis. The substance of Kant’s critique of the ideas of these two groups of philosophers treated what their questions about human thinking revealed about the character of thought. Take, for example, the question of the nature of the existence of time and space, of “extension” as René Descartes had formulated it. It is impossible for any human to grasp any phenomenon without mentally fixing that phenomenon in space and time. The rationalists identified time and space as innate features of human consciousness, while the empiricists saw them as developing as a result of experience. Kant argued that both approaches assumed that the mind was passive in its reception of phenomena, but he asserted that, in fact, the mind is an active participant in the framing of phenomena, and that time and space are transcendent categories that exist at a precognitive level. In other words, time and space are best understood, not as innate or learned phenomena, but as part of the very character of the mind as a tool. Said a third way, like the teeth of a saw or the tip of a screwdriver, time and space are attributes that help give the mind its identity as a tool. The mind has other characteristics, such as the capacity to distinguish quality and quantity, features that aid its capacities to frame mentally the phenomena it engages. Understanding the mind, and what it brought to the process of understanding thus became for Kant the very goal of philosophy itself, although in the time since he wrote, his ideas have tended to become more and more the preserve of cognitive psychologists rather than philosophers.

Philosophy and the Enlightenment

The lifespan of the Enlightenment is one of those topics upon which there is no consensus among historians. Older treatments of the subject were content to have the Enlightenment end just in time for the start of the French Revolution. More recently, as a result of the influence of the French philosopher Michel Foucault, many have come to see the Enlightenment as synonymous with the entire sweep of modern culture. Thus some have now depicted the Enlightenment as a thriving historical reality that has only in the later twentieth century been called into question by “Post-Modern” theory. Both these arguments for a “short” and a “long” Enlightenment associate the movement primarily with the rise and decline of the philosophes centered in Paris. While granting the importance of the Enlightenment as it happened in other locales, historians almost always come back to the salons of Paris. At the same time it must be admitted that the philosophes had very little to say in the great eighteenth-century philosophical debates that captivated Europe’s intellectuals. In the heyday of the French Enlightenment, in the middle of the eighteenth century, very little philosophy emerged from Paris. Instead it was the ideas of figures like Hume and Kant, with their emphasis on problems of consciousness, that were to become the most relevant contributions to existing debates within philosophy. And while the ideas that Rousseau promoted in Paris in the 1750s and 1760s were a significant departure in philosophy that were to become more important in the decades that followed, those ideas had not been formulated in the Parisian milieu. Rousseau, in fact, was an émigré who developed his thought in relative isolation before coming to Paris. It seems fair to conclude, then, that the Enlightenment, as defined by historians, and philosophy were two ships that passed in the night. Such a conclusion, though, prompts three questions. The first is “What connections existed between the Enlightenment and philosophical discourse?” Primarily, the Enlightenment development of a culture of coffeehouses and salons broadened the audience for philosophical thought, although very few of the new “bourgeois” readers seems to have read Hume and Kant directly. Instead they learned of these debates through the writings of others who popularized their ideas, just as Sigmund Freud and Albert Einstein came to be known to most twentieth-century readers, not firsthand, but through the works of others who summarized their conclusions. A second question that arises is “Did the Enlightenment have any essential impact on the development of philosophy?” A better, though counterfactual, version of this question would be, “Would Hume and Kant have written their works even if the Enlightenment had not occurred?” The answer here must be yes, given the evidence of the ideas that went into the work of these two men. Even though the Enlightenment helped to popularize serious philosophy, it should be kept in mind that serious philosophy was propelled forward by an impetus only tangentially related to the concerns of the Enlightenment. A third question is “Did the Enlightenment have any lasting legacy on the development of philosophy?” Another way of putting this question would be, “Did the Enlightenment contribute anything to the mix that produced Rousseau’s new departure?” Here also the answer must be yes. This answer requires some brief explanation. As much as Rousseau was a forerunner of Romanticism, he was equally a forerunner of the type of public figure readers demanded by the end of the eighteenth century. The Enlightenment’s constant discussion of how society might be improved focused intellectual attention on the question of the role of government in directing society. The philosophes left the task of forcing the government to fulfill its obligation to lead to those in power. Rousseau made it squarely the task of the participants in civil society to hold government to its duties. As he argued, the path forward to liberty ran through collective effort. Rousseau synthesized the public reaction to the movement for political reform, a game at which French Enlightenment philosophes had been playing over the previous decades, and forge it into a new paradigm of political action. In that sense he was an ancestor to Tom Paine, Thomas Jefferson, and the other Americans who interpreted the Enlightenment primarily in terms of politics.

Political Philosophy


In Europe, political philosophy had come into its prime during the sixteenth century, prompted by the great political, military, and religious events of the period which inspired numerous treatises aimed at resolving the problems confronting rulers. The most significant problems rulers faced in the era arose from resistance to the state’s ever-growing demand for revenue. By the sixteenth century the “Military Revolution” sparked by the introduction of guns and cannons was well underway. Princes either had to keep up with the latest military technology or risk becoming a victim of it. The only way to keep up with technological innovation was with money, and the only way to get money was through taxes. Raising taxes, however, angered taxpayers and risked rebellion. Princes thus faced a dilemma. They might tempt neighboring states by ignoring defense but keep their subjects happy. Or they could frighten off their neighbors but make their subjects unhappy through the imposition of unpopular taxes. Most chose the latter course, but in doing so, their subjects began to respond with increasing vehemence that kings were violating longstanding contractual notions of government. The religious problems of the age further complicated relationships between princes and their people, and religious turmoil often provided a further justification for rebellion. If the prince was Catholic and the subject Protestant, the argument went, the subject had a right to defend his “true” religion against the encroachments of the state.

Divine Right of Kings

As a response to both kinds of arguments—those that opposed new taxes and those that sought to defend “true religion”—royal apologists of the day began to promote the doctrine of the “divine right of kings.” Princes were, in the words of the English king James I (r. 1603-1625), “God’s lieutenants on Earth.” As such, subjects owed the same obedience to their king as they owed to God. Yet merely identifying a “divinely instituted” right to rule did not answer the bristling dilemmas that were raging all the same about just when and how a king might exercise his authority. To justify the increasingly enlarged view of royal power, sixteenth-century political theorists had turned to examine issues about sovereignty. They had argued that since the king had the final say in formulating laws, he, in fact, stood above the law, and was consequently the “absolute” authority in the nation. As James I again observed, “Kings were the authors and makers of the laws, and not the laws of the Kings.” By the early seventeenth century, ideas of divine right, which asserted that the prince derived his authority from God, combined with these ideas of absolutism, thus producing new theories of divine right absolutism. In his True Law of Free Monarchies (1598), James I first gave expression to its key tenets. Sir Robert Filmer (1588-1653), an apologist for the absolutist ambitions of James and his descendents, wrote his Patriarcha (1680) to give such theories biblical support, although during the period of rising Puritan ascendancy in England he did not dare to publish his thoughts. Patriarcha appeared only after Filmer’s death and the Restoration of the Stuarts to the English throne. Like many previous works, Filmer treated the state as a “family writ large,” and the king as its father. But then he went on to trace a line of descent of princely fathers that started with Adam and ended with Charles I, the reigning monarch in England when he was writing. The greatest developer of such theories of divine right absolutism was Bishop Jacques-Bénigne Bossuet (1627-1704), perhaps the most influential churchman in France during the first half of Louis XIV’s reign. As he argues in his posthumously published Statecraft Drawn from the Very Words of the Holy Scripture (1707) the person of the king is “sacred,” and to attack him in any way is “sacrilege.” It is through rulers, Boussuet explains, that God “exercises his empire.” The power of the prince, he concludes, is “absolute,” although he recommends that kings exercise this authority with humility. Against the enormous power of a prince, the people’s only power exists in their own innocence.


In Leviathan (1651), the work generally recognized as the first great text of modern political science, Thomas Hobbes (1588-1679) set out to make a case for absolutism that did not build upon such religious notions. Like his younger contemporary John Locke, Hobbes gained the patronage of a great aristocratic family very early in his career, and was drawn into politics from that family’s vantage point. The Cooper family that employed Locke had republican sympathies, and Locke wrote in defense of constitutionalism. The Cavendish family that maintained Hobbes was royalist, and Hobbes’ political writings all make the case for monarchy. As tutor to the second and third earls of Devonshire, Hobbes spent a good deal of his life traveling the Continent. During these tours he added to his outstanding command of Greek and Latin—the abilities that first brought him to the attention of the Cavendish family—an expertise in geometry and optics. These interests helped shape Hobbes’ approach to writing about politics, furnishing him with a concern to establish first principles from which other arguments might be deduced. While Hobbes had this rationalist instinct, he may also be viewed as an empiricist before the fact. Hobbes was among the first writers to advance a mechanistic explanation for the operations of the human mind, mapping the path sensations travel through thoughts to actions. In 1640, sensing the coming outbreak of civil war in England, Hobbes resettled in Paris, where, with the situation in England clearly in mind, he turned to writing about politics. Among the works he completed during his eleven-year stay in France the Leviathan (1651) stands out from the others, not for the uniqueness of its ideas—all Hobbes’ political writings defend royal absolutism—but for the completeness of its case. Hobbes begins there with a discussion of human psychological motivations, focusing on the desire for pleasure and the fear of death as powerful stimuli in producing human actions. Hobbes then proceeds to discuss how different political systems accommodate these forces before he turns to consider the “state of nature” that exists wherever and whenever there is no common consent for a form of government. In such a state, where everyone acts out of pure self-interest, every human being will be at war, and because of this, human life will be “solitary, poor, nasty, brutish, and short.” In this state of nature, human desires and motivations cannot possibly produce positive outcomes. Thus human society needs government to help human beings realize their own ambitions. Hobbes rejects, in other words, the idea that some human beings have been born with a “divine right” to rule over others. There are differences in strength and intelligence among individuals, but every individual has the capacity to kill every other. Hobbes’ point is that government is by definition a result of mutual agreement. Behind every form of government there is at least an implicit compact or covenant that acknowledges the rights individuals give over in exchange for government protection. But the question that lingers for Hobbes is which form of government is the best? He concludes that in a state ruled by a constitution, there will always be disagreement over whose interpretation of the constitution takes priority. Thus in constitutional states an inescapable tendency toward war will exist. The best form of government is rather an absolutist monarchy where the ability of one individual to serve and protect the polity is not compromised by the self-interest of any other individual or group in the state.

English Constitutionalism

Hobbes attempted to put the argument in favor of absolutism on a “scientific” footing. In his Two Treatises on Government (1689), Locke made a similar effort for constitutionalism. Locke’s two treatises are not just important as foundation texts of political science, however. They played a crucial role in restructuring the political debate in England after the Glorious Revolution of 1688. In seventeenth-century England the constitutional structures favored by the middle and laboring classes were different from that supported by the rich and powerful. Eventually, it was the constitutionalism this latter group supported that won the day, and Locke’s arguments in his Two Treatises was used to justify this development. “When Adam delved and Eve spanned, Who was then a gentleman?” was the pithy phrase that had once been the rallying cry of English peasants during Wat Tyler’s Rebellion in the 1380s. The phrase had reappeared around 1600, a fact that points to the challenges to the political status quo that were being mounted in England by the lower classes. Puritanism had helped to create a high level of literacy in England and had provided many ordinary people with the intellectual skills to participate in the great debate over absolutism versus constitutionalism. While the pamphlets written and read by ordinary folk made use of religious arguments, they also used historical arguments based in the “myth of the Norman Yoke.” This notion alleged that monarchy in England had only dated from the eleventh-century Norman Conquest. William the Conquerer, in other words, had done away with the simple democracy that had reigned in the country’s Anglo-Saxon past, and had subjected English people to a tyranny of aristocracy and monarchy. During the English Civil Wars the Levelers, a movement of ordinary folk, tried to re-establish a democratic republic in the island. The Levelers captured a good deal of sympathy and support in the lower echelons of the New Model Army, the Puritan force that eventually defeated Royalists. As the English Civil Wars were drawing to a close in 1647, the Putney Debates took place. These were a series of debates that pitted the New Model Army’s rank-and-file soldiers, who represented the “people” of England, against their superiors, who defended the interests of England’s political and economic elite. During the course of the debates one soldier expressed the hope that “all inhabitants that have not lost their birthright should have an equal voice in Elections.” To this, General Ireton, who represented the New Model Army’s officers responded that only those who had a “permanent fixed interest in the country should be allowed to vote.” Here Ireton was reaffirming the traditional practice that stipulated that only those men who paid an annual tax of 40 shillings should enjoy the franchise. Few of the Levelers were convinced, and it was only after violent repression that their movement fell apart.

Locke’S Response to the Call for Democracy

Although the Leveler movement was eventually suppressed, the sentiments that its adherents expressed did not die out in later seventeenth-century England. In his Two Treatises, Locke addressed the lingering view that property qualification was a tool of oppression that had its origins in the “Norman Yoke.” In Locke’s constitutional theory he developed a notion of the state of nature that was very different from that of Hobbes’s Leviathan. He argued that individuals extract from the environment valuable things by virtue of their hard work. Property arises from these efforts, and should therefore be protected by the state, along with life and liberty, as a fundamental, natural right. Government, he reasoned, came into existence through the efforts of property holders, who organized themselves under some form of authority to protect their interests. Thus Locke concluded there had never been a time when everyone had “an equal voice in Elections.” Rather, from its very first existence, government had been concerned to protect the property of those with a “fixed permanent interest” in a state. Such arguments proved immensely popular in late seventeenth-century England, where the political instability caused by problems of the Stuart succession bred fears of a resurgent radicalism among the country’s political elites. Locke’s constitutional ideas as expressed in the Two Treatises became cherished ideas among the aristocracy and gentry, people of vast interests in land. But they were also embraced by the growing class of merchants and commercial men, who were anxious to protect the wealth they were acquiring.

The Spirit of the Laws

At the end of the eighteenth century Europeans looked across the Atlantic and saw in the nascent state created out of Britain’s former North American colonies a living testament to their own political ideas. It was obvious to all who had read Locke, for example, that the rights declared to be inalienable in the American Declaration of Independence—those that allowed for the search for “life, liberty and the pursuit of happiness”—had been inspired from Locke’s Two Treatises on Government (with the anti-democratic word “property” changed to the less offensive “pursuit of happiness”). Those who had read Jean-Jacques Rousseau could recognize that the very way in which the political nation was conceptualized by the former colonists referred back to Rousseau’s The Social Contract. It took a bit more learning, however, to appreciate that the boldest application of European political thought was to be discovered in the American Constitution, which articulated a principle first found in the Baron de Montesquieu’s The Spirit of the Laws (1748): the idea that the power to rule must always be shared among competing governmental offices. Montesquieu’s ideas are as fundamental to understanding the political philosophy of the eighteenth century as Adam Smith’s The Wealth of Nations (1776) is to comprehending the age’s economic theory. Charles-Louis de Secondat, Baron de Montesquieu (1689-1755), was an outstanding example of France’s noblesse de robe, a category of bureaucratic nobles that received their titles for the services of administration they offered the crown. Montesquieu was trained as a lawyer, and then inherited the position of president of the Parlement of Bourdeaux, a regional court based in that city. He served in that capacity for eleven years before his fame as a writer made him a celebrity. That fame arose largely on the basis of his Persian Letters, a scathingly satirical critique of European society revealed through the imaginary letters of two Persian travelers in Europe. The profits generated from that work allowed Montesquieu to sell his office in the Parlement of Bordeaux and to concentrate on his writing. Montesquieu brought the sensibilities of a working bureaucrat to the task of explaining how government works. Thus the point he seeks to drive home in The Spirit of the Laws is that the greatest danger confronting any government arises from the threat of despotism. He understands despotism as being the logical result of allowing all discretionary authority to fall into the hands of any one official. The way to keep despotism in check, Montesquieu thus outlines in The Spirit, is to balance the discretionary power in the hands of one official with that of other officials in other parts of the government. In Montesquieu’s view, the goal of government is not to protect property, as it was for Locke, but to maintain liberty, and he understands liberty to mean the freedom to do those things that do not harm others. It is a given, according to Montesquieu, that those who are endowed with power will ultimately abuse their authority and harm others. And so the best government is one that limits the opportunities for officials to exercise discretionary powers in this way. He identifies three different sources of government power that arise from decision-making powers in the executive, legislative, and judicial functions of governing. In the best government those who exercise any one of these functions will necessarily have to compete for authority against the other two offices, and thus this “balance of power” will cancel out the tendency for any one official to use his power indiscriminately.


The sophistication of Montesquieu’s analysis reminds modern scholars of the impact that Europe’s political theorists had in fashioning modern systems of democratic and constitutional rule. From the Renaissance, Europe’s seventeenth-century political theorists had inherited a curiosity about the arts of government and the state of affairs that had existed in primitive societies. Political theory, too, had been catapulted into the center of Europe’s intellectual discussions by the rise of divine right absolutism in many states around 1600, a controversial development that had produced both apologists and critics of the rising authority of monarchs and the state. While many royal apologists argued that such conditions were “natural” and divinely established, others like Thomas Hobbes built trenchant defenses for strong governmental authority by examining the “state of nature” that existed before governments arose. Although Hobbes supported strong monarchical authority, he also shifted the boundaries of discussions of political theory by basing his conclusions on seemingly scientific analysis, rather than biblical or religious precedents. His Leviathan ranks as one of the great intellectual contributions of the Age of Absolutism. Yet its chief arguments in favor of absolutism were soon superseded by the clamor of others like Locke, who argued in a more optimistic vein for greater political participation across the spectrum of a state’s inhabitants. Those who followed Locke fashioned new ways of examining the powers of the state in an effort to try to unlock the secrets they hoped might allow good government and human liberty to co-exist. Montesquieu’s Spirit of the Laws, then, stands as one mature expression of this attempt to fashion government that conforms to the needs of human society. That society, as the political philosophers of the Enlightenment were often convinced, was composed of a humankind that was fractious and wont to exercise despotic tyranny, but which was all the same charged with the intellectual powers and restraint necessary to exercise self-rule.