Age of Enlightenment

• 1. Introduction

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  Dare to know. That short Latin command, sapere aude, sits at the heart of an essay Immanuel Kant published in 1784, titled Answering the Question: What Is Enlightenment? Kant defined the Age of Enlightenment as humanity's release from what he called its self-incurred tutelage, the inability to use one's own understanding without direction from another. This was the European movement of intellectual and cultural flourishing that emerged in the late 17th century and reached its peak across the 18th. It prized reason, empirical evidence, and the scientific method. It pushed for individual liberty, religious tolerance, and natural rights. But scholars have never agreed on when it began, where its borders lay, or even what to call it. Some date its start to Descartes in 1637, others to the death of Louis XIV in 1715. Who carried these ideas into coffeehouses and royal courts? How did a movement built on doubt end up undermining kings and churches? And why did its grand promise of progress stop so sharply at the edge of a slave plantation?

• 2. Two Lines Of Reason

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  Cogito, ergo sum. With that dictum, I think therefore I am, Rene Descartes built his philosophy on a method of doubt, systematically disbelieving everything unless there was a well-founded reason to accept it. The historian Jonathan Israel argues that Enlightenment thought split into two distinct lines. The moderate variety, following Descartes, Locke, and Christian Wolff, sought accommodation between reform and the traditional systems of power and faith. The moderate line tended to be deistic. It looked for compromise rather than rupture. The Radical Enlightenment took its inspiration from Baruch Spinoza, whose Tractatus of 1670 and Ethics of 1677 asserted the unity of matter against Descartes' split of mind and body. This radical tendency advocated democracy, freedom of expression, and the eradication of religious authority, separating morality entirely from theology. Pierre Bayle launched the popular and scholarly critique of religion early in the 18th century. A skeptic, Bayle drew a strict boundary between morality and religion, and the rigor of his Dictionnaire Historique et Critique shaped many of the Encyclopedie's contributors. Israel rejects attempts to treat these revolutionary ideas as mere by-products of social and economic change, insisting instead that the ideas themselves drove the transformations to come.

• 3. The Age Of Academies

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  By 1789 there were over 70 official scientific societies across Europe, a growth so striking that Bernard de Fontenelle called the 18th century the Age of Academies. These bodies had largely replaced universities as the centers of research, chartered by the state to provide technical expertise and granted the power to oversee their own publications and elect their members. Contemporary sources drew a sharp line between the two institutions: universities existed to transmit knowledge, while societies existed to create it. Antoine Lavoisier's experiments were used to build the first modern chemical plants in Paris, and in 1783 the Montgolfier brothers launched the first manned flight in a hot air balloon. Voltaire and Emilie du Chatelet popularized Newtonianism for an increasingly literate public, often through the great reference work of the age. Not everyone celebrated this faith in experiment. Jean-Jacques Rousseau criticized the sciences for distancing man from nature and for failing to make people happier. When Isaac Newton died, the poet James Thomson wrote A Poem to the Memory of Sir Isaac Newton, mourning the loss and praising the legacy of a man Thomas Jefferson would later rank among the three greatest who ever lived.

• 4. The Encyclopedie

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  Thirty-five volumes, 150 contributors, and twenty-one years of labor between 1751 and 1772: the Encyclopedie was among the most influential publications the Enlightenment produced. Denis Diderot and Jean le Rond d'Alembert compiled it, and it carried the movement's ideas across Europe and beyond. By the mid-18th century the French Enlightenment had found its focus in this single project, with Paris as the center of philosophic and scientific activity challenging traditional doctrines. The early French movement gained ground under the support of Madame de Pompadour, the mistress of Louis XV. Voltaire and Rousseau argued for a society based on reason rather than faith and Catholic doctrine. They wanted a civil order grounded in natural law and a science built on experiment and observation. D'Alembert's Preliminary Discourse to the work offered its own history of the Enlightenment, a chronological list of advances in knowledge with the Encyclopedie itself standing as the pinnacle. The Encyclopedistes were the heirs of Bayle's skepticism, and their habit of applying rationality to every problem is what many historians consider the essential change of the era.

• 5. The Social Contract

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  In 1651, Thomas Hobbes opened a new debate with Leviathan, arguing that all legitimate political power must be representative and rest on the consent of the people. Hobbes laid down fundamentals of European liberal thought: the rights of the individual, the natural equality of all men, and the artificial character of the political order. John Locke based his governance philosophy on social contract theory and is known for the claim that individuals have a right to life, liberty, and property, with the right to property derived from labor. Locke defined the state of nature as a condition in which all men are born equal and rational, following natural law. When one citizen breaks that law, transgressor and victim enter a state of war, and so people form civil society to protect their rights through an unbiased judge such as a court. Rousseau began from the opposite premise, that civil man is corrupted while natural man wants nothing he cannot supply himself. For Rousseau, people join civil society through the social contract to achieve unity while preserving freedom, a freedom embodied in the sovereignty of the general will. Not everyone accepted the contract. David Hume's essay Of the Original Contract held that governments rarely derive from consent and rest instead on a ruler's habitual authority and force. Adam Ferguson agreed, and in his 1767 An Essay on the History of Civil Society used a four-stage theory to explain how humans advance from hunting and gathering to commercial society without ever signing a contract.

• 6. Philosopher Kings

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  Voltaire despised democracy. He insisted that an absolute monarch must be enlightened and act as reason and justice dictated, in other words be a philosopher-king. The leaders of the Enlightenment were not especially democratic, and they often looked to absolute rulers as the key to imposing reforms designed by intellectuals. Historians call these rulers enlightened despots. Frederick the Great ruled Prussia from 1740 to 1786 and patronized philosophers and scientists at his court in Berlin. Frederick described his principal occupation as combating ignorance and prejudice, enlightening minds, and making people as happy as human nature allows. Voltaire, who had been imprisoned and maltreated by the French government, eagerly accepted Frederick's invitation to live at his palace. Catherine the Great of Russia corresponded with Voltaire and hosted world-class scientists in residence, including Leonhard Euler and Peter Simon Pallas. Joseph II of Austria proved over-enthusiastic. He announced so many reforms with so little support that revolts broke out, his regime became a comedy of errors, and nearly all his programs were reversed. In Poland the model constitution of 1791 expressed Enlightenment ideals but lasted only a year before the nation was partitioned among its neighbors.

• 7. The Limits Of Liberty

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  Two-thirds of the enslaved people in the colony of Saint-Domingue had been born in Africa. When the Haitian Revolution broke out in 1791 and ran until 1804, those rebels drew on specific notions of kingdom and just government from West and Central Africa and used religious practices such as voodoo to form revolutionary communities. A common theme across the countries that imported Enlightenment ideas was the deliberate exclusion of those ideas from the question of slavery. France's revolutionary government had denounced slavery, the account goes, but the property-holding revolutionaries then remembered their bank accounts. The pressure of the revolt forced the French National Convention to abolish slavery in 1794. Toussaint Louverture had read the critique of European colonialism in Guillaume Thomas Francois Raynal's Histoire des deux Indes, and was struck by Raynal's prediction of a coming Black Spartacus. Even so, European nations and the United States refused to support Saint-Domingue's anti-colonial struggle. The era's blind spots ran deeper still. The rights of women and nonwhite people were generally overlooked in a philosophy that was often explicitly Eurocentric. Scientific racism first emerged here, joining traditional racism to new research methods, as the rival theories of monogenism and polygenism debated whether all races shared a single origin. Against this current, Mary Wollstonecraft argued in her 1792 work A Vindication of the Rights of Woman that women, like men, should be treated as rational beings.

• 8. A Contested Inheritance

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  By 1794, conservative and clerical critics pointed to the Reign of Terror during the French Revolution as confirmation of everything they had predicted. From the start they had attacked materialism and skepticism as evil forces encouraging immorality. Romantic philosophers charged that the movement's excessive dependence on reason ignored the bonds of history, myth, faith, and tradition needed to hold a society together. Sir Isaiah Berlin later gave this opposition a name, the Counter-Enlightenment, which defended traditional religious and political authorities against rationalist critique. According to Keith Thomas, supporters hail the Enlightenment as the source of everything progressive in the modern world, standing for freedom of thought, religious tolerance, and hope for the future, while detractors accuse it of shallow rationalism and naive optimism. The movement's reach was global and uneven. The Haskalah brought it to the Jews of Central and Eastern Europe, the Nahda awakened Arab regions of the Ottoman Empire, and in Japan the slogan Civilization and Enlightenment grew potent by the 1880s. A variety of 19th-century movements, including liberalism, socialism, and neoclassicism, trace their intellectual heritage to this period. The latest proposed endpoint for the whole age is a single date: the death of Immanuel Kant in 1804.