The world didn't end during the early years of the Christian community, despite the apostle Paul's imminent predictions.
It didn't end in 1914, although WWI gave people quite a scare. It also didn't end on May 21, 2011, to the chagrin of popular evangelist and radio broadcaster Harold Camping, who predicted the date of the apocalypse several times during his career.
Apocalyptic teachings, including the idea that God intends for the world as we know it to cease to exist, have been part of both Christianity and Islam since their beginnings. In the U.S., around 1 in 5 adults say the apocalypse will happen in their lifetime, a figure that's stayed relatively constant over the past century.
"I think thinking about the end of days is not quite as foreign to us as we might like to think," said Graeme Wood, the Edward R. Murrow Press Fellow with the Council on Foreign Relations who has studied apocalyptic thought in Islam.
With the rise of ISIS, apocalyptic worldviews have taken on new significance. Members of the terrorist group justify horrific violence with their beliefs that they have a crucial role to play in bringing about the end of the world.
"Much of what the group does looks nonsensical except in light of a sincere, carefully considered commitment to ultimately bringing about the apocalypse," wrote Wood in his 2015 feature article for The Atlantic, "What ISIS Really Wants."
When high-profile apocalyptic predictions are proven wrong, nonbelievers might be tempted to mock those who actively await the end of the world. But in order to confront groups like ISIS, one must understand them, and it would serve government officials, religious leaders and other people of faith well to take the apocalypse seriously, experts said.
"A lot of people feel that this is kind of an outmoded worldview," said Bernard McGinn, a historian at the University of Chicago Divinity School. But apocalyptic beliefs "don't go away. They're always with us."
Pre- or postmillennialism
Apocalyptic beliefs are inspired by religious texts and encouraged by popular religious writings.
"All three of the monotheistic faiths have aspects of apocalypticism, extreme and also generalized," McGinn said.
Passages from the Old Testament prophets, teachings of Jesus and the Apostle Paul, and the book of Revelation ground Christian apocalyptic teachings, which instruct believers to await Jesus Christ's return and expect the world to change when he arrives.
"But the day of the Lord will come like a thief, and then the heavens will pass away with a loud noise, and the elements will be dissolved with fire, and the earth and everything that is done on it will be burned up," reads 2 Peter 3:10.
Premillennialists — a group that includes many evangelical Christians — believe this destruction will be preceded by a period of demise. Only true believers will be safe during the battle between the forces of good and evil.
"The scenario is a very complicated combination of hope for good things and fear of evil things," McGinn said.
Apocalyptic hope is widespread among American evangelicals, according to a 2010 Pew Research Center survey.
Nearly 6 in 10 white evangelical Protestants (58 percent) think Jesus Christ probably will return by 2050, compared with 27 percent of white mainline Protestants, Pew reported.
Mainline Protestants may read the same biblical passages about the apocalypse as evangelicals but most interpret them symbolically rather than literally. And members of this group who do believe in an actual end of the world usually think of it very differently than other apocalyptic Christians, said Sean McCloud, an associate professor of religious studies at the University of North Carolina at Charlotte.
"For mainline Protestants, if the world as we know it is going to end, it's just going to get better and better," he said, noting that people with this worldview are called postmillennialists.
One might assume that this postmillennialist mindset would be more compelling. Who wants to wish for the world's destruction?
But premillennialism can be comforting in its own way, especially if you're dissatisfied with the direction society or your life is going, McCloud said.
"Growing feelings of powerlessness and distrust in institutions tend to make notions of an end time coming more prevalent," he added.
By having confidence that the end of the world is coming soon, people are asserting that their actions and decisions matter, said Jason Bivins, an associate professor of religious studies at North Carolina State University.
"The sense that we're living at the edge of an apocalyptic event gives (someone's) life significance where it might not otherwise have it," he said.
Why the apocalypse matters
Beyond affecting someone's mindset, apocalyptic beliefs shape behaviors. Someone who is certain that Jesus Christ will return to earth in their lifetime and upset the current order won't care as much about efforts to improve society.
"People who oppose, for example, anything related to climate change could say, 'Well, you know the world will end. There's nothing we could or should do about it,''' McGinn said.
Premillennialists may engage in an election season and rally around certain candidates, but politics won't be their core concern, Bivins said.
They often have a "deep resignation about the ability to change anything," he noted.
This attitude may frustrate people who don't share this apocalyptic worldview, but it's not exclusive to believers. There are many nonreligious people who couldn't care less about social justice activism or politics.
What's more concerning is when someone's sense that the end of the world is coming leads to violence, scholars said.
"Apocalyptic belief, given the right circumstances, can serve radical ends," wrote respected apocalypse scholar Paul Boyer in his 1992 book, "When Time Shall Be No More: Prophecy Belief in Modern American Culture."
In the case of ISIS, apocalyptic teachings have played a role in the deaths of thousands, Wood said, noting that "ISIS has many people who are doing things that have very little explanation other than the fulfillment of the will of God."
Wood argued in his Atlantic article that efforts to combat ISIS must acknowledge and address apocalypticism, rather than dismiss it as foreign or simply part of the organization's propaganda.
Similarly, McGinn said the best way to respond to apocalyptic communities is to try to put yourself in their shoes. He added that crises in the past like the 1993 raid on the Branch Davidians in Waco, Texas, would have been avoided if government officials took apocalyptic worldviews seriously.
"It's far better to try to understand them," than to mock or dismiss their beliefs, he said.
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