It's been said that the suicide bombers who cause the scenes of carnage and chaos relayed on American TV screens and front pages must be driven by a cocktail of religious fanaticism and outright insanity.
However, some experts -- including people who are advising the U.S. government on terrorism -- said not only are suicide bombers sane, but also that anyone of us, under the right circumstances, could become one.
"Absolutely, this is normal psychology, normal group dynamics," said Clark R. McCauley, a Bryn Mawr College psychology professor who is part of an outside team consulting for the Department of Homeland Security.
"Normal people, given the right circumstances or right set of friends, can become suicide bombers," said Marc Sageman, a forensic psychiatrist and former CIA officer.
"None of the suicide bombers would be put in a mental asylum on the order of the district psychiatrist," said Ariel Merari, one of the leading Israeli experts on suicide bombers, who has interviewed dozens of attackers captured before they could kill.
McCauley even finds insight into the terrorist mind from, of all sources, Abraham Lincoln's Gettysburg Address. He points to a passage from Lincoln's speech on giving up one's life for a cause: "From these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion."
It is part of McCauley's argument that suicide bombers see themselves like the dead of Gettysburg -- sacrificing their lives for a greater good to ensure, in Lincoln's words, "that we, here, resolve that these dead shall not have died in vain."
In short, the experts kept saying suicide bombers are not necessarily irrational, and noted that lots of people in lots of places have been honored by their societies for choosing to kill themselves in order to kill others. Japanese kamikaze pilots in World War II did it. So have Tamil guerrilla fighters in Sri Lanka. And closer to Western civilization, there is the Biblical account of Samson, who pulled down a temple to kill his enemies, which meant killing himself.
"Part of the power of suicide bombing is the impact of martyrdom," McCauley said. "Once it's somebody that you know and somebody that you care about that has taken his or her life in this fashion, that has made the sacrifice, then there is a kind of a guilt associated with doing less than they were willing to do."
That is McCauley's point about Lincoln. Obviously, Lincoln was not calling for suicide attacks, but he was trying to mobilize the troops to fight harder to honor those who had died already.
That dynamic, according to McCauley, is now in play in an Internet world where each new attack turns into a recruiting event for others: Bomb-making instructions are given out. Examples are set. And if you're a young man in a group of young men, you will get inspired.
"I think anybody could become a suicide bomber," said Sageman, the former CIA officer. "It's a process."
Sageman saw such a process in America in connection with the massacre at Columbine High School in Colorado. There, the two boys who killed others and themselves got their inspiration from a wider group.
"The guys in Columbine, although they were two, they were very much connected to a whole community on the Internet," he said.
End Justifies the Means?
Many would call it madness to kill innocents, including children, on a bus or train and to call it good. But in Israel, where it has been practically a weekly experience at times, Merari is convinced the attackers can tell themselves it is good and still be sane.
"What they say is, 'All Israelis are potentially soldiers. Israeli children are going to grow up and become Israeli soldiers,' " he said. "And that justifies their killing."
Outside the Middle East, how does the rational suicide bomber call it good to kill Americans in an office building or British people on a train?
"The kind of justification that is commonly employed," McCauley said, "is something about desperation: 'We're weak and they're strong. This is the only way we can hit back at them.' "
But when did the West ever deliberately hurt children? Many in the Muslim world might point to Iraq in the 1990s.
"Through much of the Muslim world, and even some of Europe," McCauley said, "it's believed that the embargo on Saddam Hussein's Iraq caused the deaths of several hundred thousand people, most of them children, from bad water, untreated sewage, lack of proper medical care."
ABC News' John Donvan originally reported this story for "Nightline" on July 29, 2005.