Next Saturday marks the beginning of the end of days. Or at least that is what the Christian radio broadcaster Harold Camping and his many followers think. By Mr. Camping's calculations, May 21 is the day when Jesus will return to judge all of humankind and to gather up the faithful.
But what will happen the following day, when this prophecy falls short? Doomsayers almost never admit that they were wrong; they usually become even more adamant about the truth of their beliefs, using various rationalizations to spin-doctor the nonevent into a successful prediction.
Nor do religionists hold a monopoly on forecasting the end of days. There are secular versions as well, from Karl Marx's certainty about the approaching demise of capitalism to various modern doomsday scenarios involving overpopulation, resource depletion, nuclear winter, Y2K, solar flares, super volcanoes and, of course, global warming.
Why are such apocalyptic prophecies so common in human history? What are their emotional and cognitive underpinnings?
In most doomsday scenarios, destruction is followed by redemption, giving us a sense of both fear and hope. The ostensible "end" is usually seen as a transition to a new beginning and a better life to come. For religionists, God destroys Satan and sinners and resurrects the virtuous. For the secular-minded, humanity atones for its sins through political, economic or ideological enlightenment.
Marxists saw communism as the liberating climax of a multistage evolutionary process. Environmentalists usually conclude their forecasts of calamity with earnest recommendations for how to save the planet. Or consider John Galt, the hero of Ayn Rand's anti-collectivist novel "Atlas Shrugged" and an inspiration for many of today's tea-party activists. In the book's final apocalyptic scene, the heroine Dagny Taggart turns to Galt and pronounces, "It's the end." He corrects her: "It's the beginning."
Cognitively, there are several other processes at work, starting with the fact that our brains have evolved to be pattern-seeking belief engines. Imagine yourself as a hominid on the plains of Africa three million years ago. You hear a rustle in the grass. Is it the wind or a dangerous predator?
If you guess that it's a dangerous predator but it's just the wind, you've made a mistake-believing that something is real when it's not (a "false positive," as cognitive scientists call it)-but a rather harmless one. On the other hand, if you guess that the rustle in the grass is the wind but it turns out to be a hungry lion, your mistake is more serious: The lion was real but you thought it wasn't (a "false negative"). In this case, you're lunch, and you won't get the chance to be more cautious next time.
In our ancestral environments, vigilance and rapid reactions often made the difference between life and death, so the default position was to assume that all patterns are real. It was simply safer, from the point of view of survival, to hear rustling in the grass as a warning of danger. Moreover, our ancestors saw meaning and intention ("agency") in these patterns: They took rustling in the grass to mean that a predator was intent on eating them.
What does any of this have to do with our apocalyptic tendencies? Doomsday scenarios are patterns based on our perceptions of the passage of time. We tend to make causal connections among events-A causes B, which causes C, which causes D, etc.-simply because they follow one another chronologically. These patterns are often false, of course, but they are correct often enough that, in our brains, time and causality are inseparably linked. We thus tend to infuse the passage of time with meaning and to see agency in it as well, whether it takes the form of God's supernatural agency in settling moral scores or nature knocking us off the pedestal of our technological hubris.
Apocalyptic visions help us to make sense of an often seemingly senseless world. The literal meaning of apocalypse is an "unveiling" or "revelation," and this definition of the word holds true whether we consider St. John's narrative in the book of Revelation or secular chronologies that fit the events of history into a larger cosmic design.
For human beings, it is much easier to suffer the slings and arrows of outrageous fortune when we believe that it is all part of a deeper, unfolding plan. We may feel like flotsam and jetsam on the vast rivers of history, but when the currents are directed toward a final destination, it gives us purpose and meaning. We want to feel that no matter how chaotic, oppressive or evil the world may be, all will be made right in the end.
Mr. Shermer is the publisher of Skeptic magazine and a monthly columnist for Scientific American. The latest of his many books, "The Believing Brain: From Ghosts and Gods to Politics and Conspiracies," will be published later this month.