A comprehensive history of modern Christianity on both sides of the Atlantic has yet to be written. There are several difficulties that must be overcome before such a project can be undertaken. First, there is a remarkable unevenness of research. Although there are many studies on religion in America, and although American historians with few exceptions acknowledge the role of religion in nineteenth- and twentieth-century American history, within a largely secularized European historical profession a secularized conception of modern history has led to the result that the impact of religion in the periods after the Reformation has often been neglected, if not ignored. Before a comparative study of religion in the Old World and the New World can be undertaken, what is needed, therefore, is a series of penetrating studies on religion in Europe that can be matched with corresponding American works.

What we know, moreover, is very contradictory. In particular, views on religion in America are quite controversial. On the one hand, there are strong voices that serve to demonstrate the strength of religion in America. Alexis de Tocqueville was among the first foreign observers to point out that “there is no country in the world where the Christian religion retains a greater influence over the soul of men than in America.” In America, he stated in the 1830s, Christianity “reigns without obstacle” and “by universal consent”; in the United States “religious zeal,” in his view, was “perpetually warmed” by “the fires of patriotism” as “despotism may govern without faith, but liberty cannot.” While in France “the spirit of religion and the spirit of freedom” were “marching in opposite directions,” “they were intimately united” in America and “reigned in common over the same country.” The strong materialism of Americans, Tocqueville concluded, produced an even stronger interest in things immaterial.