The scale of Tuesday's terror inspires comparisons to other ages -- inevitably, to other wars. The greatest single-day U.S. catastrophe since the Civil War. The longest suspension of major league baseball and New York Stock Exchange trading activity since the First World War. The most momentous attack on the nation's way of life since Pearl Harbor -- a second "day of infamy" that some say calls for an official U.S. war declaration.

But the war metaphor is an awkward fit. The best way to make sense of Tuesday's attack is by reference not to another age of history, but another age of man. The terrorists who turned planes into guided missiles are best thought of as hate-filled, overgrown adolescents. In 1999, the bloodiest high school massacre in U.S. history was perpetrated in Littleton, Colo. by Dylan Klebold and Eric Harris. According to Harris's diary, his larger dream was not just to kill classmates, but also to hijack a plane and crash it into New York City. Tuesday's attack was his vision.

Various commentators have taken U.S. politicians to task for using the term "cowardly" to describe the terrorists who struck on Tuesday. Evil, misguided, murderous -- yes; but also brave, for they were willing to die violently for their cause. But if that is true, then Harris and Klebold must also have been brave, for they committed themselves to their rampage with no less certainty of death.

In fact, neither Klebold and Harris nor the terrorists who attacked on Tuesday were "brave" according to any normal definition of the word. What they were was "rash." "The man who exceeds in confidence about what really is fearful is rash," Aristotle wrote. "The rash man, however, is also thought to be boastful and only a pretender to courage."

How can someone court death yet be "only a pretender to courage?" According to Daniel Weinberger, director of the Clinical Brain Disorders Laboratory at the National Institutes of Health in the United States, there is a physiological basis: The capacity to control impulses that arise from feelings of anger and vengeance is lodged in the prefrontal cortex, which is not fully formed in humans until we are at least 20. The ramifications of this go straight to Aristotle's definition. "I doubt that most school shooters intend to kill, in the adult sense of permanently ending a life and paying the price for the rest of their own lives," Dr. Weinberger wrote in The New York Times earlier this year. "Such intention would require a fully developed prefrontal cortex, which could anticipate the future and rationally appreciate cause and effect. The young school shooter probably does not think about the specifics of shooting at all. The ... lack of apparent remorse illustrates how unreal the reality is to these teenagers."

The teenage suicide bombers who attack Israel fall into this category. Adult terrorists, a category that likely includes those who executed Tuesday's attack, do not. But whatever their age, Muslim extremists ("Islamists" as they are often known) do not "rationally appreciate" the cause and effect of their actions for another reason: quasi-pornographic promises of eternal bliss. Families of Arab suicide bombers typically explain terrorists' motivation as outrage at alleged Israeli and Western persecution. What gets less ink is the fact that Islamist leaders promise "martyred" terrorists that unlimited sex with virgins awaits them in paradise. In an interview televised a few years back, jailed terrorist organizer Mohammed Abu Wardeh repeated a claim that is often used to recruit suicide bombers. "God would compensate the martyr for sacrificing his life for his land," he said in Arabic. "If you become a martyr, God will give you 70 virgins, 70 wives and everlasting happiness." Thus indoctrinated, Middle Eastern Islamist fanatics may be seen as adult Klebolds and Harrises -- their violent, utopian ideology substituting functionally for a teenager's lack of brain development.

The analogy goes deeper than this, however. In the same New York Times article, Dr. Weinberger also wrote of the psychological motivation behind teenage rampage attacks: humiliation. "In the face of ridicule," he notes, "they may want revenge." Twelve years ago, in his book on Middle Eastern history and sociology, The Closed Circle: An Interpretation of the Arabs, David Pryce-Jones put things in similar terms: "Acquisition of honor, pride, dignity, respect and the converse avoidance of shame, disgrace and humiliation are keys to Arab motivation." Thus do Arab mobs occasionally seek to "burn [Western-style] buildings ... They are façades, imitating the West in order to ward off the charge of being 'backward' and 'uncivilized' ... What otherwise seems ... self-destructive in Arab societies is explained by the anxiety to be honored and respected at all costs, and by whatever means ... Shame is a living death."

It is this psychology that makes fighting terrorists so difficult. Most belligerents seek to conquer land and resources -- a threat that can be easily defended by Western armies. But Islamists are more concerned with avenging their perceived humiliations -- the humiliations that modernity implicitly imposes on technologically primitive, politically backward Arab theocracies. Like bitter gun-toting teenagers bent on going out in a blaze of suicidal fury, Islamists act under the evil and tragically misguided view that the mere act of murder -- even the murder of innocents -- feeds their dignity.