"We the people," begins the Zambian constitution's preamble. It sounds familiar to Americans, but a few words later is a phrase that American Christians haven't ever heard: "declare the Republic a Christian nation while upholding the right of every person to enjoy that person's freedom of conscience or religion."

It's not just lip service. Zambia's laws draw on Christian tradition to ban, for example, both homosexual behavior and pornography. Earlier this year, a Zambian judge sentenced a German tourist to six years in jail with hard labor—for oral sex. "Customs of other countries, which are an abomination here, must not be allowed to be practiced by tourists or anybody," the judge said.

It's not just a political thing, either. More than 80 percent of the country's 9 million residents are professing Christians—and the numbers are growing. By 2025, predicts The World Christian Encyclopedia, 87.8 percent of the country will be Christian. By 2050, it should top 92 percent.

This is a country where Christianity infuses every aspect of the culture. Christian music—from local bands to Dolly Parton's gospel hits—is everywhere. It greets visitors in the airport. It plays in the taxis. There are radio stations that play exclusively Christian music, of course, but the mainstream stations have dance mixes that intersperse "Sunny, yesterday my life was full of rain" and "Gimme! Gimme! Gimme! A man after midnight" with "Let the words of my mouth and the meditation of my heart be acceptable in thy sight, O Lord."

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Zambia is a Christian nation.

Zambia is also the living legacy of David Livingstone, a missionary who became one of the most famous men of the 19th century. When Livingstone died in 1873, his African companions made a year-long ...