Preacher and evangelical broadcaster Harold Camping has announced that Jesus Christ will return to Earth this Saturday, May 21, and many of his followers are traveling the country in preparation for the weekend Rapture. They’re undeterred, it seems, by Mr. Camping’s dodgy track record with end-of-the-world predictions. (Years ago, he argued at length that the reckoning would come in 1994.) We’ve yet to learn what motivates people like him to predict (and predict again) the end of the world, but there’s a long and unexpected psychological literature on how the faithful make sense of missed appointments with the apocalypse.

The most famous study into doomsday mix-ups was published in a 1956 book by renowned psychologist Leon Festinger and his colleagues called When Prophecy Fails. A fringe religious group called the Seekers had made the papers by predicting that a flood was coming to destroy the West Coast. The group was led by an eccentric but earnest lady called Dorothy Martin, given the pseudonym Marian Keech in the book, who believed that superior beings from the planet Clarion were communicating to her through automatic writing. They told her they had been monitoring Earth and would arrive to rescue the Seekers in a flying saucer before the cataclysm struck.

Festinger was fascinated by how we deal with information that fails to match up to our beliefs, and suspected that we are strongly motivated to resolve the conflict—a state of mind he called “cognitive dissonance.” He wanted a clear-cut case with which to test his fledgling ideas, so decided to follow Martin’s group as the much vaunted date came and went. Would they give up their closely held beliefs, or would they work to justify them even in the face of the most brutal contradiction?

The Seekers abandoned their jobs, possessions, and spouses to wait for the flying saucer, but neither the aliens nor the apocalypse arrived. After several uncomfortable hours on the appointed day, Martin received a “message” saying that the group “had spread so much light that God had saved the world from destruction.” The group responded by proselytizing with a renewed vigour. According to Festinger, they resolved the intense conflict between reality and prophecy by seeking safety in numbers. “If more people can be persuaded that the system of belief is correct, then clearly, it must, after all, be correct.”

When Prophecy Fails has become a landmark in the history of psychology, but few realize that many other studies have looked at the same question: What happens to a small but dedicated group of people who wait in vain for the end of the world? Ironically, Festinger’s own prediction—that a failed apocalypse leads to a redoubling of recruitment efforts—turned out to be false: Not one of these follow-ups found evidence to support his claim. The real story turns out to be far more complex.

What Festinger failed to understand is that prophecies, per se, almost never fail. They are instead component parts of a complex and interwoven belief system which tends to be very resilient to challenge from outsiders. While the rest of us might focus on the accuracy of an isolated claim as a test of a group’s legitimacy, those who are part of that group—and already accept its whole theology—may not be troubled by what seems to them like a minor mismatch. A few people might abandon the group, typically the newest or least-committed adherents, but the vast majority experience little cognitive dissonance and so make only minor adjustments to their beliefs. They carry on, often feeling more spiritually enriched as a result.

For those who draw their inspiration from the Bible, there is some small print in Deuteronomy 18:21-22 which wonderfully illustrates why a failed prophecy may not shake the foundations of a believer’s faith, or cause him any uncomfortable cognitive dissonance.

You may say to yourselves, “How can we know when a message has not been spoken by the LORD?” If what a prophet proclaims in the name of the LORD does not take place or come true, that is a message the LORD has not spoken. That prophet has spoken presumptuously, so do not be alarmed.

Only predictions that come true are from God, you see, while failed prophecies are just down to human slip-ups—a truly divine response to anyone who would condemn either a prophet or a whole belief system on the minor matter of a failed apocalypse.

Even without this sacred disclaimer, it’s easy enough for a believer to reinterpret and revise the details of a prediction so that it fits whatever facts are on the ground. The research literature is littered with such examples. When atomic energy didn’t sweep over the Earth to herald the Second Coming on Christmas Day 1967, the Universal Link group cheerfully reinterpreted their prophecy as pertaining to a spiritual force, rather than a physical effect. When flying saucers never announced their presence to humankind in 1976, the Unarian sect gently reworked its prophecy to refer more broadly to some point in “the future,” while blaming limited human minds for misunderstanding the aliens’ grand plan. When a Pentecostal group led by the God-channelling housewife Mrs. Shepard emerged after more than a month from self-built fallout shelters, they were pleased that the divinely ordained nuclear holocaust had not come to pass—and grateful for having passed a test of their faith.

In fact, so many studies have been conducted on unfulfilled prophecies from religions large and small that they were compiled into a fascinating book from 2000, Expecting Armageddon. None of the groups described reacted to the unexpected persistence of the world with a zealous drive for new members, and most made just minor adjustments to their beliefs. If Harold Camping’s followers remain steadfast in their devotion come Sunday afternoon, don’t be surprised—it’s merely a testament to the human spirit.

For those not waiting for the world to end in a storm of fire and light it is easy to write off the believers as deluded, but Festinger was not so wide of the mark when he suggested that we adapt to even the most unlikely of contradictions using nothing more than our methods of everyday rationalization. The faithful could just as easily be those who stubbornly stand by disgraced politicians, failed ideologies, dishonest friends, or cheating spouses, even when reality highlights the clearest of inconsistencies. Armageddon is unlikely to arrive this weekend, but most of us have lived through it many times before.