The Enlightenment was a movement of international dimensions, with thinkers traversing borders in a constant exchange of visits, letters, and printed materials. The Republic of Letters was a truly cosmopolitan set of networks stretching from western Europe to its colonies in the Americas, to Russia and eastern Europe, and along the routes of trade and empire to Africa and Asia. Within this broad international conversation, scholars have identified regional and national particularities.

The Scottish Enlightenment, which was centered in Edinburgh, was marked by an emphasis on common sense and scientific reasoning. A central figure in Edinburgh was David Hume (1711–1776), whose emphasis on civic morality and religious skepticism had a powerful impact at home and abroad. Building on Locke’s teachings on learning, Hume argued that the human mind is really nothing but a bundle of impressions. These impressions originate only in sensory experiences and our habits of joining these experiences together. Because our ideas ultimately reflect only our sensory experiences, our reason cannot tell us anything about questions that cannot be verified by sensory experience (in the form of controlled experiments or mathematics), such as the origin of the universe or the existence of God. Paradoxically, Hume’s rationalistic inquiry ended up undermining the Enlightenment’s faith in the power of reason.

Another major figure of the Scottish Enlightenment was Adam Smith. In An Inquiry into the Nature and Causes of the Wealth of Nations (1776), Smith attacked the laws and regulations that, he argued, prevented commerce from reaching its full capacity (see Chapter 17).

The Enlightenment in British North America was heavily influenced by English and Scottish thinkers, especially John Locke, and by Montesquieu’s arguments for checks and balances in government. Leaders of the American Enlightenment, including Benjamin Franklin and Thomas Jefferson, would play a leading role in the American Revolution (see Chapter 19).

After 1760, Enlightenment ideas were hotly debated in the German-speaking states, often in dialogue with Christian theology. Immanuel Kant (1724–1804) was the greatest German philosopher of his day. Kant posed the question of the age when he published a pamphlet in 1784 entitled What Is Enlightenment? He answered, “Sapere Aude [dare to know]! ‘Have the courage to use your own understanding’ is therefore the motto of enlightenment.” He argued that if intellectuals were granted the freedom to exercise their reason publicly in print, enlightenment would almost surely follow.

Northern Europeans often regarded the Italian states as culturally backward, yet important developments in Enlightenment thought took place in the Italian peninsula. In northern Italy, a central figure was Cesare Beccaria (1738–1794), a nobleman educated at Jesuit schools and the University of Pavia. His On Crimes and Punishments (1764) was a passionate plea for reform of the penal system that decried the use of torture, arbitrary imprisonment, and capital punishment, and advocated the prevention of crime over the reliance on punishment.