The Enlightenment's first ground was laid at the end of the seventeenth century. Newton's *Principia Mathematica* (1687) unified earth and sky under a single mathematical law; John Locke's *Essay Concerning Human Understanding* (1689) defined the mind as a blank slate, and his *Two Treatises of Government* (1689) tied political authority to the consent of the governed. Within a generation these two strands — mathematical success in natural science, and critique of tradition in politics and epistemology — fused, in the European educated class, into a bold claim: the method of reason had proved itself in nature; the same method should work in law, morals, religion and politics. Immanuel Kant, in his 1784 essay "What is Enlightenment?", caught that attitude in a single imperative: *sapere aude*, dare to use your own understanding.

The movement was less a book than an infrastructure. In eighteenth-century Paris, salons hosted by women such as Madame Geoffrin; in London, coffee-houses; in Edinburgh, clubs; in Berlin and Königsberg, reading societies — together created semi-public spaces in which ideas could be discussed across class and profession. The *Encyclopédie* of Denis Diderot and Jean le Rond d'Alembert, published in 28 volumes between 1751 and 1772 — 71,818 articles, the largest publishing project of the century — is the lasting monument of that infrastructure: the claim that everything, from artisanal know-how to astronomy, can be translated into a common language testable by reason. Voltaire fought religious intolerance through *Candide* (1759) and dozens of pamphlets; Jean-Jacques Rousseau argued in the *Social Contract* (1762) that legitimate power derives from the 'general will'; in Scotland David Hume subjected causation and religion to a corrosive critique, and Adam Smith wrote the *Wealth of Nations* (1776).

The political consequences were direct. Locke's theory of property and the right of resistance passed almost verbatim into the opening paragraphs of the American Declaration of Independence in 1776. Rousseau and Montesquieu shaped France's first constitution of 1789 and the Declaration of the Rights of Man and of the Citizen. The Enlightenment was at the same time the chief engine of secularisation: it questioned the Church's monopoly on knowledge and education, normalised the separation of state from religion, and gave currency to deist or frankly philosophical substitutes for revelation. The modern university, public education and the language of liberty and equality, all consolidated in the nineteenth century, are in large part the long downstream of this ground.

The contradiction that should not be airbrushed: the same century that proclaimed reason universal also saw the industrialisation of the Atlantic slave trade and the expansion of European empire. Hume's notorious 1753 footnote and numerous passages from Kant's lectures contain explicit racist judgements about non-European peoples; in the same period Diderot and Condorcet wrote forceful anti-slavery texts, but the Enlightenment as a whole did not hold consistently to its own principles. That contradiction is now a central question in re-reading the movement: is its universalist language a real programme of emancipation, or a self-portrait in which European male reason declares itself the measure of humanity? Most current historians answer 'both': the tools the movement left — critique, public reason, the language of rights — were the very tools later used by anti-slavery and anti-colonial movements against the Enlightenment's own blind spots. NOTE: the technical history of rationalism (Descartes, Spinoza) and empiricism (Locke, Berkeley, Hume) as philosophical traditions is treated separately on the philosophy track; this entry reads the Enlightenment as a socio-cultural movement.