The scientific and intellectual developments of the 17th cent.—the discoveries of Isaac Newton, the rationalism of Réné Descartes, the skepticism of Pierre Bayle, the pantheism of Benedict de Spinoza, and the empiricism of Francis Bacon and John Locke—fostered the belief in natural law and universal order and the confidence in human reason that spread to influence all of 18th-century society. Currents of thought were many and varied, but certain ideas may be characterized as pervading and dominant. A rational and scientific approach to religious, social, political, and economic issues promoted a secular view of the world and a general sense of progress and perfectibility.
The major champions of these concepts were the philosophes, who popularized and promulgated the new ideas for the general reading public. These proponents of the Enlightenment shared certain basic attitudes. With supreme faith in rationality, they sought to discover and to act upon universally valid principles governing humanity, nature, and society. They variously attacked spiritual and scientific authority, dogmatism, intolerance, censorship, and economic and social restraints. They considered the state the proper and rational instrument of progress. The extreme rationalism and skepticism of the age led naturally to deism; the same qualities played a part in bringing the later reaction of romanticism. The Encyclopédie of Denis Diderot epitomized the spirit of the Age of Enlightenment, or Age of Reason, as it is also called.