Yet America today has easily the highest rate of regular church attendance of any Western nation, while recent political controversies have shown the enduring significance of religious belief in shaping policy. Supreme Court rulings on abortion and school prayer, to take just two divisive issues, helped create the so-called 'moral majority' which influenced the courts and Congress, as well as helping elect Ronald Reagan and George Bush. Few political commentators discuss this.
Similarly, the defining political issue of United States history - slavery and what to do about it - requires analysis that takes full account of how evangelical Protestants reacted to the great sectional conflict which brought secession and civil war. Textbooks rarely explain it. Yet as Richard Carwardine points out in this illuminating and powerful book, the American Revolution of 1776 cannot be understood as a purely secular event, but as one shaped by the religious revivalism of the Great Awakening of the 1740s. He shows, with clarity and elegance, how the second Great Awakening between 1800 and 1840 influenced the crisis which ultimately led to Confederates firing on Fort Sumter in April 1861.
Using the vast correspondence of Methodist, Baptist and Presbyterian ministers and laymen, the evangelical press and popular political newspapers, Dr Carwardine places Protestant evangelical reaction to slavery within not just the political maelstrom of the 1850s but social and economic change too. Western expansion, industrial growth, railways, urbanisation and immigration were transforming the nation's political economy, while universal white male suffrage functioned through a party system that made the US the envy of democrats the world over.
Within this context, slavery was not simply a moral and political problem for Protestants: it threatened evangelical unity. Evangelical churches flourished in slave states and free, so the task initially was to evolve a system of worship and belief that divided least. The problem was compounded by the fact that because slavery existed everywhere in the world Christ had known, there was no firm theological foundation for condemning the peculiar institution. Yet as Abraham Lincoln put it: 'If slavery is not wrong then nothing is wrong.' So the struggle to reconcile conscience with political reality is in a sense the unifying theme of this compelling book.
Dr Carwardine harmonises his theme with others. For example, evangelical fears that the slave power 'conspiracy' would be combined with a Roman Catholic one grew in the decade after 1845 as starving peasants swamped New York, New England and other states following the Irish potato famine. Leaders of the Catholic church had no problem with slavery: they endorsed it where it existed, as did the Democratic party. So when Irish-Catholic immigrants voted for the Democrats, the natural governing party in the slaveholding South by the 1850s, evangelical fear of being overcome by a 'conspiracy' between Rome and slavocracy deepened.
There is much to admire in this beautifully produced book. Its author is steeped in the ethos of antebellum America, and has spent more than a decade reading, reflecting and letting his knowledge and ideas mature. At times he seems to identify too closely with his protagonists. Yet his complete command of sources enables him to fulfil the historian's most important task: seeing the world through the eyes of the people he is writing about, while discussing them in a detached and disinterested way.
'God prosper the right' was the response of evangelicals to the perceived threats to their passionate faith. Yet by the time Lincoln was elected in November 1860, communication across the Mason-Dixon line had virtually ceased. When war came, both sides implored the same God grant them victory in a struggle which cost the lives of more young American men than any in history.