It begins with an account of eighteenth-century European and American intellectual, political, and social life. He describes the universities, academies, salons, and reading societies from which the principal ideas of the Enlightenment emerged and examines their diffusion, interaction, and influence. Enlightenment ideas provided a basis at once for democracy, enlightened despotism, and anarchy; they informed the great revolutions in France and America and the regimes that followed them; they were the center and the cause of the great flowering of learning that took place throughout the European world.
In conclusion the book examines the progress of Enlightenment thought in the nineteenth century, the counter-movement of Romanticism, and the degree to which reason and rationality continue to hold sway at the turn of the twentieth century.