It has long been taken for granted that the ideas of the European Enlightenment--of men like Locke, Hume, Voltaire, or Rousseau--profoundly affected America during the Revolutionary age. Yet there has been no full-length analysis of the movement of ideas from Europe to America in the late 18th century. Now one of American's leading intellectual historians has written a magisterial book that fills the gap. May defines the Enlightenment broadly. Men of the Enlightenment were all those who believed that their own age was more enlightened than the past and that man and nature are best understood through the use of natural faculties. He treats the Enlightenment as a 'religion', even though many of its leading proponents opposed organized religion. Throughout the book he relates the Enlightenment to Protestant Christianity, for it is out of the clashes and reconciliations between those two systems that 19th-century American culture--a culture that lasted almost to our own time--took shape. Defined so broadly, the religion of Enlightenment obviously included many different kinds of people--deists and skeptics and liberal Christians, aristocrats and democrats, conservatives and revolutionaries. May divides the European Enlightenment into four major categories, and shows how each had a different effect in America. Obviously some ideas could be transmitted more easily than others to a society overwhelmingly Protestant and rapidly becoming democratic. May shows how the Enlightenment affected the thoughts and actions of major figures like Jefferson, Franklin, and John Adams, but these familiar figures are treated against a background of less well-known people--doctors and ministers, scientists and planters and politicians. Beginning with the movement of relatively conservative British Enlightened ideas to America before the Revolution, May moves on to the transmission of the skeptical thought of men like Voltaire and Hume, and the revolutionary prophesies and programs of Rousseau, Condorcet, and Paine. The climax of the book comes in the 1790s, when radical Enlightened ideas clashed head-on with New England's religious and social traditions. The last part of the book shows how some aspects of the European Enlightenment were assimilated and others rejected by the American society of the 19th century.