During the eighteenth century the Enlightenment flourished, advocating liberal values, critical reason, secularism, and future progress. This movement took root in the institutions of the secular public culture that emerged during the late seventeenth century. These institutions, in which women often participated, included salons and coffee houses that encouraged egalitarian intellectual discussion; and Masonic lodges that offered an alternative to conventional religion and schooled their members in habits of self-governance. Equally important were the free presses of England and the Dutch Republic, and the scientific academies that popularized the ideas of the Scientific Revolution. This public culture also fostered the attacks on traditional Christianity by skeptics such as Bayle and Hume, free thinkers including Toland, and deists. The most important of these anticlerical critics was Voltaire who, inspired by the work of Newton and Locke, attacked superstition and blind acceptance of religious authority.

Enlightenment philosophes contributed important ideas to political, social, and economic thought. Drawing upon the secular political ideas of Machiavelli and Hobbes, thinkers including Locke, Montesquieu, and Rousseau developed concepts of contractual government, limited royal power, checks and balances, and the general will. Locke's epistemology inspired philosophes to advocate educational reform, the most radical of which was envisioned by Rousseau. These reforms advanced furthest in Protestant countries, but Enlightenment ideas continued to find their most enthusiastic supporters in the salons rather than the universities. Humanitarian philosophes, most notably Beccaria, called for the abolishment of torture and reform of criminal justice systems. Although some philosophes expressed ambivalence regarding slavery, others attacked it, contributing to the debates that led to its abolition in some countries. This humanitarianism also prompted debate concerning social equality, debate that in itself represented democratic ideals. Confident in the effects of self interest, Smith articulated the principles of modern market capitalism, and the French physiocrats developed rational theories of agricultural economy. The publication of Diderot's and d'Alembert's Encyclopedia inaugurated the High Enlightenment, during which younger philosophes attacked clerical and aristocratic privilege with an intellectual violence that later found political expression in the radical French Revolution.

Enlightenment ideals had little effect on European power politics. Enlightenment humanitarianism did not reduce warfare, which was waged throughout the century by the great powers for continental and imperial hegemony. War was one of the principal tools of the enlightened despots who used Enlightenment principles to build powerful, centralized, monarchical states. In eastern Europe, Enlightenment reformers succeeded most where Catholicism was weakest. Farther west Enlightenment ideals along with traditions of self-government and religious dissent drove the American Revolution, whose leaders ultimately built a constitution based on principles of equality, balanced government, and the rule of law.

The Enlightenment culminated the trend initiated by the Renaissance and advanced by the Scientific Revolution. To the modern West, Enlightenment thinkers passed on a secular vision of humanity, confidence in the autonomous intellect, habits of tolerance and rational inquiry, and political ideas that fed the growth of liberal democracy.