Software creators on both sides say they are only trying to help others see the truth. But most applications focus less on scholarly exegesis than on scoring points.

One app, “Fast Facts, Challenges & Tactics” by LifeWay Christian Resources, suggests that in “reasoning with an unbeliever” it is sometimes effective to invoke the “anthropic principle,” which posits, more or less, that the world as we know it is mathematically too improbable to be an accident.

It offers an example: “The Bible’s 66 books were written over a span of 1,500 years by 40 different authors on three different continents who wrote in three different languages. Yet this diverse collection has a unified story line and no contradictions.”

“The Atheist Pocket Debater,” on the other hand, asserts that because miracles like Moses’ parting of the waters are not occurring in modern times, “it is unreasonable to accept that the events happened” at all. “If you take any miracle from the Bible,” it explains, “and tell your co-workers at your job that this recently happened to someone, you will undoubtedly be laughed at.”

These applications and others  like “One-Minute Answers to Skeptics” and “Answers for Catholics”  appear to be selling briskly, if nowhere near as fast as the top sellers among the so-called book apps in their iPhone category: ghost stories, free books and the King James Bible.

Sean McDowell, the editor of “Fast Facts” and some textbooks for Bible students, said he has become increasingly aware of a skill gap between believers and nonbelievers, who he feels tend to be instinctively more savvy at arguing. “Christians who believe, but cannot explain why they believe, become ‘Bible-thumpers’ who seem dogmatic and insecure about their convictions,” he said. “We have to deal with that.”

Image “The Atheist Pocket Debater.” Credit... Damon Winter/The New York Times

“Nowadays, atheists are coming to the forefront at every level of society  from the top of academia all the way down to the level of the average Joe,” added Mr. McDowell, a seminary Ph.D. candidate whose phone app was produced by the B&H Publishing Group, one of the country’s largest distributors of Bibles and religious textbooks.