The eighteenth-century movement committed to reason, individual rights, equality before the law and the critical examination of inherited authority — the claim that no institution, text or office is exempt from having to justify itself at the bar of argument.
It was never a single program, and its national forms differed sharply. The Scottish Enlightenment of Hume and Smith was empirical, sociological and comparatively friendly to religion and custom; the French philosophes — Voltaire, Diderot, Montesquieu — were more combative toward the church and produced in the Encyclopédie (1751-72) a deliberate instrument for redistributing knowledge; the German Aufklärung was more concerned with the conditions of knowledge itself, culminating in Kant's essay of 1784, which defined enlightenment as humanity's emergence from a self-imposed immaturity and gave the movement its motto: dare to know. Rousseau belongs to the period while dissenting from much of it, arguing that the civilization it celebrated had corrupted what it claimed to improve.
Scholars now distinguish a moderate Enlightenment, which sought to reconcile reason with existing religious and political order, from a radical one running back through Spinoza that pressed toward democracy, materialism and full toleration. The distinction matters because it explains how the same movement could produce both cautious constitutional reformers and genuine revolutionaries. Wollstonecraft is among its most rigorous figures precisely for holding it to its own standard, insisting that principles proclaimed as universal had to apply to women or be abandoned as pretense.
The Enlightenment has been criticized from within the philosophical tradition it founded — by Adorno and Horkheimer, who argued its instrumental reason ended in domination, and by postcolonial scholars who note that its universalism coexisted with empire and, in several of its major figures, with explicit racial hierarchy. Its defenders generally concede the historical record and argue that the standards by which those failures are now condemned are themselves Enlightenment standards, which is not a small thing to have supplied.