The search for the propellant of the killer-madness in Cho Seung-Hui tells us more about disorders in American thought than about those of the murderer. Recall first and foremost that the crime was quickly identified as the "bloodiest shooting attack in American history" done by a single person. We accepted this, but quickly rejected its corollary: namely, that if it was that -- the most violent rampage in 231 years of history -- then it had some claim to be called unique. In fact it differs in magnitude but not in kind from shootings in which 23 or 19 people were killed.

If a man jumps out of an airplane window at 25,000 feet and survives, it is understandable that there should be public curiosity about how he managed to do so, and scientists will wish to probe the event intending to illuminate, presumably for the benefit of ambitious acrobats, what made it possible. But when the causes of an event are inside a person's mind, such probing is a waste of time, and on the order of presumption.

Intensive study of April 16 could succeed in telling us various ways the script might have been changed to spare Cho's 32 victims. How? Well, an armed guard might have been retained for every classroom. Wonderful idea! But as the French say, "une fausse idee claire": a terrific idea that doesn't work. There are 500 classrooms at Virginia Tech.

Well, another idea would be to have barred the lethal weapons from the scene. But doing that would require a kind of cultural revolution, one at great variance with Southern traditions. Yes, such a ban might have been instituted anyway, and yes, efforts might have been made to enforce it, but guns go off in many places where they are illegal. Ask Google about murders in New York City.

Well, Cho Seung-Hui had a history of mental imbalance, and had actually spent time in a mental-health facility -- from which, however, he had been discharged, as evidently fit to mingle in society. Does this tell us the simple story that standards are loose, too loose, and Cho Seung-Hui and all others like him should be isolated?

That reasoning brings to mind J. Edgar Hoover's testimony after the assassination of President Kennedy. The killer, Lee Harvey Oswald, had a security record that included time in the Soviet Union, for which he professed sympathy; a mysterious week in Mexico City during which he tried to obtain a Cuban visa; and membership in a political organization that pleaded for "Fair Play for Cuba." Hoover's observation: If I removed from access to presidential itineraries everyone with indiscretions the equivalent of Oswald's, I'd have to lock up 500 people whenever a president visited Chicago.

So then, despairing of external measures, the scientists went to work. Here is a digest of one report, written by John Schwartz and Benedict Carey for The New York Times:

"People with so-called avoidant personality disorder shun social situations because of a paralyzing dread of disapproval or criticism. Those with paranoid personality disorder nourish a deep distrust of others and see insults and malicious meanings in almost every interaction. Both are stubborn patterns of behavior that can begin in adolescence or earlier, and in his influential book, 'Disorders of Personality' (Wiley, 1996), Dr. Millon identifies a blend of the two as 'insular paranoid' disorder."

Long live the scientists. Continued...