The Age of Enlightenment (also called the Age of Reason) was a broad intellectual and cultural movement that flourished in Europe and its colonies roughly from the late 17th century through the late 18th century. Enlightenment thinkers argued that human reason, empirical observation, and open debate could reform society, government, and knowledge itself—displacing reliance on inherited tradition, absolute monarchy, and ecclesiastical authority.
Core ideas included natural rights, religious toleration, the separation of powers, popular sovereignty, the social contract, freedom of speech and the press, and a confidence in scientific progress. Key figures and works frequently cited include John Locke's Two Treatises of Government (1689), Montesquieu's The Spirit of the Laws (1748), Voltaire's polemics on tolerance, Jean-Jacques Rousseau's The Social Contract (1762), Denis Diderot and Jean d'Alembert's Encyclopédie (1751–1772), Immanuel Kant's essay What Is Enlightenment? (1784), Adam Smith's The Wealth of Nations (1776), and Cesare Beccaria's On Crimes and Punishments (1764).
The movement was not monolithic. Scholars often distinguish national variants: the Scottish Enlightenment (Hume, Smith, Ferguson), the French philosophes centered on Parisian salons, the German Aufklärung, and an American strand expressed by figures such as Benjamin Franklin and Thomas Jefferson. Sociable institutions—coffeehouses, academies, Masonic lodges, and the rapidly expanding print market—spread ideas across borders.
For IR and political-theory purposes, the Enlightenment is foundational. It supplied the vocabulary of modern constitutionalism (used in the U.S. Declaration of Independence of 1776 and the French Déclaration des droits de l'homme et du citoyen of 1789), early international-law thinking that built on Grotius and Pufendorf, and Kant's Perpetual Peace (1795), a touchstone for democratic-peace theory. Later critics—from counter-Enlightenment conservatives like Edmund Burke to 20th-century theorists Max Horkheimer and Theodor Adorno in Dialectic of Enlightenment (1947)—have challenged its universalist claims and its entanglement with colonialism and slavery.
Example
Drafters of the U.S. Declaration of Independence in 1776 drew heavily on Enlightenment ideas, particularly John Locke's account of natural rights and government by consent.
Frequently asked questions
Most historians date it from the late 1600s—often anchored to Locke's 1689 Two Treatises—through the late 1700s, with the French Revolution of 1789 commonly marking its political climax.
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