In 1986, on his fortieth birthday, George W. Bush suddenly stopped drinking. He refused to go into the reasons behind his decision, other than to allude to boyish pranks and glancing brushes with the law. What he did not mention was that he had been arrested on at least two occasions — for disorderly conduct in 1966, and for driving under the influence of alcohol in 1976. Whether he was genuinely alcoholic was less clear. Bush himself has always resisted that label, saying only that he was “addicted” to alcohol. “I wasn’t a knee-walking drunk,” he told a group of teenagers in 2007. “I had too much to drink one night, and the next day I didn’t have any.”

The truth was that Bush’s decision had little to do with his drinking. It came just as he was starting to identify himself as an evangelical Christian, and as his commitment to evangelicalism has grown, so has his commitment to abstinence as a solution to a wide range of problems — to drug abuse, to teenage pregnancies, to the aids epidemic in sub-Saharan Africa. As governor of Texas, he liked to tell teenagers to avoid all sexual activity until they had entered into a “biblical marriage relationship.” As a presidential candidate in 1999 and 2000, he talked endlessly about sexual morality. “I have been faithful to my wife,” he would say when the subject of then president Bill Clinton’s sexual transgressions came up. (When reporters pressed him on the subject and asked whether he himself had been chaste until marriage, he became evasive, saying only, “I think the thing that baby boomers have to say is not, ‘Did we make mistakes?’ but ‘Have we learned from our mistakes and are we willing to share the wisdom?’”) As president of the United States, he would preside over a vast increase in federal funding for abstinence-only sex education, with expenditures peaking at US$176 million in 2007.

My goal in writing this book is to explore why abstinence is so important to evangelicals like George W. Bush. The implications would be minimal if abstinence were a private virtue and nothing more. But as Bush’s example makes all too clear, the tendency in American history has been for abstinence to spill over into the public sphere. Temperance began as a voluntary movement and ended with Prohibition. The sexual purity movement of the late nineteenth and early twentieth centuries led to legislation that made it illegal to transport females across state lines for “immoral purposes” (the Mann Act). The New Virginity, an evangelical movement spearheaded by the Southern Baptist Convention, has shaded into the use of federal tax dollars to pressure public schools into teaching abstinence-only sex education.

Nor have the concept’s effects been confined to America. The Woman’s Christian Temperance Union went international in 1883. America’s wars on drugs have always been world wars, fought as much in that country as in the countries that supply it with drugs. The New Virginity is by its very nature a missionary movement, with outposts in Britain and sub-Saharan Africa.

The problems these movements propose to solve vary, but the underlying principle, that the only safe response to risk is to eliminate it altogether, has remained remarkably constant. That there have been so many of these movements, and that they keep returning to the same solution, suggests that the time has come to take a closer look at the religious ideal they share.

By abstinence I mean a principled and unerring refusal to engage in a particular activity. Going without something for a short period of time is not abstinence. The person who gives up meat on Fridays is not giving up meat per se; that person is simply giving up meat once a week. The abstainer is driven by an entirely different logic: if something is problematic on some occasions, then it is problematic on all occasions. Anything short of total victory is a form of defeat.

The concept is simple, but its implications are both complex and far-reaching, affecting how Americans think about their health and their indulgences — and how their government promotes the first and regulates the second. Nor does the idea show any sign of fading. On the contrary. Most Americans (79.2 per cent) do not smoke. A large minority (38.9 per cent) do not drink. Nine million (an estimated 3 per cent) do not eat meat. Four million, all of them schoolchildren, have been browbeaten into swearing off drugs. Approximately one-third of all public-school students are taught abstinence-only sex education.

Americans have sworn off so many different things at so many different times that a strictly chronological history runs the risk of becoming cluttered and unwieldy. I have opted instead to focus on the concept at crucial junctures in its development, from its origins in eighteenth-century England to its migration, in the late nineteenth and early twentieth centuries, to the American South. Each chapter examines the concept from a different angle, but all return to the same point: America’s commitment to abstinence is a function of that country’s commitment to an idiosyncratic and especially demanding strain of evangelical Protestantism. As the contours of that creed have changed, so has the face of abstinence. From its high point in the 1830s, the concept has become progressively narrower, shorn first of its social radicalism, next of its all-encompassing asceticism, and last of its post-millennial idealism. The one thing that has not changed is the faith strict evangelicals place in abstinence. More than half are teetotallers. Few use illicit drugs. Almost all continue to believe in premarital chastity.

The doctrine that guides their actions has gone by any number of names over the years — Christian perfection, sanctification, holiness, the second blessing. Its core teaching, that the Christian can conquer sin, is an article of faith among evangelical Protestants. Where they have differed is in how they define sin. The trend has been for that definition to contract over time, and with it, the number of things Americans are willing to give up. The ends abstinence serves have also undergone a startling transformation. Once the handmaiden of feminists such as Susan B. Anthony and abolitionists such as William Lloyd Garrison, abstinence today is primarily associated with conservative evangelicals, with people like James Dobson, Tim LaHaye, and, of course, George W. Bush.