Whatever might have been going on in the faraway American Colonies, 1776 was a banner year in English letters. Adam Smith's "An Inquiry into the Nature and Causes of the Wealth of Nations," the cornerstone of modern economics, was published. So was the first of the eventual six volumes of Edward Gibbon's "A History of the Decline and Fall of the Roman Empire."

Whatever you might think of some of Gibbon's conclusions, this enormous work was, in many ways, the first modern book of history. Skeptical of secondhand information, the author strove to rely on rigorous analysis of primary sources. "I...