The synthesis was a compound of evangelical Protestant religion, republican political ideology, and commonsense moral reasoning. Through the time of the Civil War, that synthesis defined the boundaries for a vast quantity of American thought, while also providing an ethical framework, a moral compass, and a vocabulary of suasion for much of the nation's public life. It set, quite naturally, the boundaries within which formal theological effort took place. Since the Civil War, the synthesis has declined in importance for both formal thought and public life, though not without leaving an enduring stamp upon the mental habits of some religious communities and episodic marks upon the public discourse.

The synthesis was most visible in the links constructed between religion and public life. As an instance, the 1833 amendment to the Massachusetts Constitution that did away with the last church establishment remaining from the colonial period nonetheless paused to affirm that "the public worship of God, and instructions in piety, religion, and morality, promote the happiness and prosperity of a people, and the security of republican government." When these words were written, Alexis de Tocqueville had only just returned to France from his memorable tour of the North American continent, and he was making the same point descriptively rather than prescriptively: "I do not know if all Americans have faith in their religion - for who can read to the bottom of hearts? - but I am sure that they believe it necessary to the maintenance of republican institutions. This opinion does not belong only to one class of citizens or to one party, but to the entire nation; one finds it in all ranks."

The synthesis operated just as manifestly at the intersection of theology and popular philosophy. Contemporaries who differed dramatically in their religious convictions were nonetheless linked tightly to each other by philosophical method. In the early nineteenth century, for example, serious differences divided Harvard's professor of logic and metaphysics, the Unitarian Levi Hedge; Yale's president and modified Calvinist Timothy Dwight; the upstart Restorationist Alexander Campbell, who was exploiting the open American environment to restore the primitive church of the New Testament; and the first professor of theology at Princeton Seminary, the conservative Presbyterian Archibald Alexander. Yet from these contentious corners of America's religious landscape resounded the same devotion to moral philosophical first principles. Dwight, in 1793, for example, set out an American credo that prevailed widely for at least the next two generations: The faculties, necessary to form a competent judge of all these facts, are the usual senses of men, and that degree of understanding which we customarily term Common-sense. . . . A plain man, thus qualified, would, as perfectly as Aristotle, or Sir Isaac Newton, know whether Christ lived, preached, wrought miracles, suffered, died, appeared alive after death, and ascended to Heaven. The testimony of the senses, under the direction of Common-sense, is the deciding, and the only testimony, by which the existence of these facts must be determined.

It was the same for Alexander in 1808 when he defended the need for divine revelation by appealing to "self-evident principles to which every rational mind assents as soon as they are proposed . . . truths in morals, in which all men do as certainly agree as in mathematical axioms." For Hedge in 1821 these same principles served as a basis for defending a position on the human will that Alexander would have found abhorrent: "The moral freedom of man is not a question of speculation, to be settled by abstract reasoning. . . . It is a question of fact to be decided by feeling. . . . We believe we are free, because we feel that we are so." Three years later, Campbell demonstrated why the creeds that elitists like Dwight, Alexander, and Hedge defended were so preposterous: "To present . . . a sectarian creed composed, as they are all, of propositions, deduced by logical inferences, and couched in philosophical language, to all those who are fit subjects of salvation of Heaven . . . for their examination or adoption, shocks all common sense." These examples only hint at the weight of custom that by the 1820s had joined Protestant precepts securely to the principles of republican and commonsense reasoning. This synthesis of religious, political, and philosophical principles was never monolithic in either public or religious spheres. But even if each of its elements was contested, the confluence of the three interpretive systems and the cultural significance of that confluence was unmistakable. For the articulation of Christian theology, this synthesis was profoundly significant. The process by which evangelical Protestantism came to be aligned with republican convictions and commonsense moral reasoning was also the process that gave a distinctively American shape to Christian theology by the time of the Civil War.

The Protestant evangelicals who came to dominate religious life in the early United States shared an emphasis on conversion, the supreme religious authority of the Bible, and an active life of personal holiness. They were the descendants of Reformed immigrants - English Puritans to New England, Scottish and Scotch-Irish Presbyterians to the middle and southern colonies, and low-church Anglicans to the Chesapeake. But nineteenth-century evangelicals were also the heirs of two full generations of revival, beginning with the Great Awakening of the 1730s and 1740s and continuing through local, episodic awakenings in nearly every region of the colonies-become-states.

By the time these evangelicals came to prominence, most Americans were already committed, as a result of the successful War for Independence, to a republican conception of politics. In this view, the exercise of political power could be sanctified by the virtue of people and magistrates, or turned into tyranny by the vices of rulers and ruled. Like the Protestantism of the early nineteenth century, this republicanism also existed in many varieties, some harking back to the classic tradition of civic humanism, others allied with a more modern liberalism, and still others featuring "Commonwealth," "country," or "Real Whig" elements.

By the late eighteenth century most Americans likewise shared both a mistrust of intellectual authorities inherited from previous generations and a belief that true knowledge arose from the use of one's own senses - whether the external senses for information about nature and society or the moral sense for ethical and aesthetic judgments. Most Americans were thus united in the conviction that people had to think for themselves in order to know science, morality, economics, politics, and especially theology. For some Americans this certainty was rooted in formal study guided by thinkers of the Scottish Enlightenment who developed careful theories concerning "common sense." For many others, including burgeoning numbers of Methodists and simple "Christians," it was a product of epistemological self-assertion that heeded no creed but the Bible.

For each aspect of the synthesis, as well as for the synthesis itself, variants abounded. Men and women often appropriated it differently. In the South it took longer to convert traditional concepts like "honor" and "virtue" to evangelical norms, but that transformation did take place. The remarkable thing, however, is not that differences existed but that they were confined within a fairly narrow range. The extent of the synthesis is suggested by its power among even Roman Catholics, whose fellow religionists in Europe remained securely opposed to all rapprochement with Protestantism, republicanism, and epistemological self-sufficiency. To sum up a situation that many historians now take for granted: after the 1780s, republicanism (wherever found along a continuum from classical to liberal) had come to prevail in America; very soon thereafter, commonsense principles (whether defined in elite or populist terms) were almost as widely spread; and in the same post-Revolutionary period, Protestant evangelicalism (however divided into contending sects) became the dominant American religion.

The way in which evangelicalism and civic humanism merged during the Revolutionary period to form a Christian republicanism has been the subject of several solid studies in the last quarter century. Although not as much attention has been paid to the marriage of evangelicalism and commonsense moral reasoning, the conjunction of the two is just as well established. As a result of much fine work, therefore, the presence - and, to some extent, the rise - of the synthesis is now thoroughly understood.

What for the most part has not been done is to show how unexpected, in the longer historical view, the emergence of the synthesis was; how much the American intellectual story differed from Protestant developments in parallel societies; how intimately the republican-evangelical-commonsense synthesis was woven into the fabric of American public life through the time of the Civil War; and how powerfully both this intellectual synthesis and Protestant participation in American public life shaped the writing of Christian theology. It is not my argument that the blending of evangelical Protestantism with republicanism and commonsense reasoning explains theological development exhaustively. Other influences did continue to have a powerful effect, including the enduring weight of theological tradition among many Catholics, Lutherans, and high-church Episcopalians, as well as in some of the more evangelical denominations. For almost all religious leaders, the Bible remained an ever-present resource, even when put to unexpectedly innovative uses. Americans in the period 1790-1865 also continued to absorb European influences, especially from England, with the strongest impulses at first from the Wesleys, then from those who founded voluntary organizations to distribute the Bible or attack slavery, then from Samuel Taylor Coleridge's intuitive Anglicanism, and then from the Oxford Movement. By the 1830s currents from Germany and France were also affecting American theology.

It is, however, indicative of the American character of theology between the Revolution and the Civil War that, even with a considerable expansion of creative biblical interpretations, almost all Scripture, whether traditional or newly recorded, was interpreted by hermeneutical canons arising from the same commonsense and republican conventions of thought. In addition, even with important influences from Europe fully acknowledged, there still was less theological borrowing from Britain and the Continent in the period between the Revolution and the Civil War than at any time before or since in American religious history.

Neither is it the contention of this book that Protestant contacts with republican politics and commonsense philosophy were the only relationships that influenced the writing of theology. The expansion of market economies, especially when linked to liberal principles about the rights of individuals, certainly became a theological as well as social factor in this period. Other systems of political thought affected theological reasoning as well, including Lockean liberalism, the traditions of the common law, and historic arguments defining a just war. Granting due weight to these other influences, it was still the case that the most distinctly American features of theology between the Revolution and the Civil War arose from the evangelical Protestant alliance with commonsense reasoning and republican ideology.