The Enlightenment: Reason, Rights and Their Limits

"Dare to know!"

In 1784 the German philosopher Immanuel Kant answered the question "What is Enlightenment?" His answer: it is humanity's release from self-imposed immaturity, the habit of letting others think for us. His motto was the Latin Sapere aude, "Dare to know" or "have the courage to use your own understanding."

The Enlightenment was not one doctrine but a conversation across Europe and the Americas, with echoes elsewhere. Its thinkers often disagreed. What they shared was confidence that reason and evidence, the methods that had worked for Newton, could improve government, law, economics and daily life.

Key thinkers and ideas

• Montesquieu, a French noble and judge, used the satirical Persian Letters (1721) to criticize French society through the eyes of imagined Persian visitors. In The Spirit of the Laws (1748) he argued that liberty requires a separation of powers among legislative, executive and judicial branches.
• Voltaire (the pen name of François-Marie Arouet) attacked religious intolerance and censorship. When a Protestant merchant, Jean Calas, was tortured and executed in Toulouse in 1762 on weak evidence, Voltaire campaigned until he was cleared (1765) and wrote a Treatise on Tolerance (1763). His satire Candide (1759) mocked blind optimism.
• Jean-Jacques Rousseau, born in Geneva, argued in The Social Contract (1762) that legitimate government rests on the general will of the people. Its opening is usually translated: "Man is born free, and everywhere he is in chains." His ideas inspired democrats and revolutionaries.
• Denis Diderot and Jean d'Alembert edited the Encyclopédie (1751–1772), a huge reference work on science, crafts and ideas, with many volumes of plates showing tools and trades. Authorities banned it at times, but it kept appearing.
• Cesare Beccaria, an Italian jurist, argued in On Crimes and Punishments (1764) against torture and the death penalty, and for punishments that are certain, prompt and proportionate.
• Moses Mendelssohn in Berlin was a leading Jewish thinker of the Haskalah (Jewish Enlightenment) and argued for religious toleration and civil rights for Jews.
• Mary Astell in England argued in A Serious Proposal to the Ladies (1694) that women deserved serious education. In a later work (1706) she asked why, if all men are born free, all women are born slaves.

Most philosophes were not atheists. Many were deists, who saw God as the creator of a rational universe run by natural laws.

How ideas spread

Ideas travelled through a new public sphere:

• Salons in Paris, often hosted by women such as Madame Geoffrin, brought writers, scientists and nobles together.
• Coffeehouses in London, Paris, Vienna and Istanbul were places to read newspapers and argue.
• Print: books, pamphlets, newspapers and journals multiplied. Where censorship was strict, books were printed in the Dutch Republic or Switzerland and smuggled in.
• Letters: scholars across Europe and the Americas wrote to one another constantly, forming a "Republic of Letters".

Enlightened absolutism

Some monarchs read the philosophes and claimed to rule as "enlightened" reformers, while keeping full power.

• Frederick II of Prussia (ruled 1740–1786) corresponded with Voltaire, called himself the "first servant of the state", largely ended judicial torture, tolerated religious minorities and promoted schools. He also seized Silesia from Austria in 1740 and kept the Junkers' power over serfs.
• Catherine II of Russia (ruled 1762–1796) wrote an Instruction (Nakaz, 1767) drawing on Montesquieu and Beccaria and called a commission to reform the laws. But after the huge peasant and Cossack revolt led by Yemelyan Pugachev (1773–1775), she strengthened nobles' power over serfs.
• Joseph II of Austria (ruled alone 1780–1790) went furthest: a Toleration Patent (1781) for Protestants and Orthodox Christians, later measures for Jews, and the abolition of serfdom in his lands. Many reforms provoked resistance and were reversed after his death.

The pattern: reforms that strengthened the state (law codes, schools, efficient taxes) often succeeded; reforms that threatened nobles' power usually failed.

The Enlightenment beyond Europe

• In British North America, Benjamin Franklin and Thomas Jefferson belonged to the Republic of Letters, and Enlightenment ideas shaped the American Revolution.
• In Spanish America, creole scholars founded scientific societies and newspapers, and some began to question Spanish rule.
• In Qing China, scholars of the kaozheng ("evidential research") movement used careful textual and historical evidence to test accepted interpretations of the classics.
• In Japan, scholars of rangaku studied Dutch science, while the kokugaku ("national learning") school turned to Japan's own ancient texts.
• Indigenous critique. In the early 1700s the French writer Lahontan published dialogues with a Wendat statesman he called Adario, often linked to the real Wendat leader Kondiaronk, who played a key role in the Great Peace of Montreal (1701). The "Adario" character criticizes French inequality, money and religion. Historians debate how much these dialogues reflect real Wendat arguments and how much Lahontan invented, but they show Europeans were hearing Indigenous criticism of their societies.

Contradictions and limits

Enlightenment thinkers proclaimed universal rights, but many did not apply them universally.

• Slavery. Some philosophes, such as Montesquieu (with bitter satire) and the authors of later editions of Raynal's history of the two Indies, attacked slavery. Yet slavery reached its peak in the 1700s, and some thinkers, including David Hume and Kant, wrote racist claims ranking human groups.
• Women. Rousseau argued in Émile (1762) that girls should be educated to please and serve men. Women hosted salons and wrote, but were excluded from universities and politics.
• Indigenous peoples. Europeans often used the stereotype of the "noble savage", which praised Indigenous peoples while denying them real complexity and history.

These contradictions were noticed at the time. Enslaved and free Black writers, women writers and Indigenous leaders turned Enlightenment language against its limits, which leads straight to the revolutions studied in The World, 1789–1900.