The eighteenth-century Enlightenment marks the beginning of the modern age, when the scientific method and belief in reason and progress came to hold sway over the Western world. In the twentieth century, however, the Enlightenment has often been judged harshly for its apparently simplistic optimism. Here a master historian goes back to the sources to give us both a more sophisticated and a more intriguing view of the philosophes, their world and their ideas.