The period of European thought known as the Enlightenment, which ran roughly from the late 17th century to the end of the 18th, produced few individual discoveries as dramatic as those of the preceding Scientific Revolution. Its significance lay elsewhere: in a gradual but profound shift in the questions that educated people were prepared to ask about politics, religion, economics and the nature of knowledge itself. By the end of the period, ideas that would have been dangerous to express in the 1680s were openly discussed in coffee houses, salons and the new periodical press.
At the centre of Enlightenment thought was the conviction that reason, carefully applied, could be used to improve human life. Writers such as John Locke argued that governments derived their legitimacy from the consent of the governed, and that citizens retained rights that no ruler could legitimately override. Adam Smith, writing a century later, suggested that economic prosperity depended less on the protection of monopolies than on the decentralised choices of free individuals. The philosopher Immanuel Kant summed up the mood in a famous essay, urging his readers to "dare to use their own understanding" rather than defer to traditional authorities.
These ideas did not spread evenly or uncontroversially. Governments often attempted to suppress writings that challenged royal authority or established religion, and several leading figures were at various times imprisoned, exiled or forced to publish anonymously. Nevertheless, the expansion of printing, rising literacy and the growth of a commercial middle class created an audience that was hungry for new ideas and willing to pay for them.
The long-term consequences were enormous. The political revolutions in America in 1776 and France in 1789 drew explicitly on Enlightenment arguments for constitutional government and individual rights. The abolition of slavery, the gradual separation of church and state, modern conceptions of tolerance and the scientific organisation of public life can all be traced, in different ways, to this intellectual ferment. Even critics of the Enlightenment typically argue with tools that it helped to shape.