Thirty-three people are dead; 32 of them innocents, gunned down by a young man who then killed himself. We want to know why. We want to understand how such a horrific thing could happen on a bucolic college campus.

Could it have been prevented? Do we need better laws? Did university officials ignore the warning signs of a dangerous young man bent on destruction? Did police fail to protect students in the hours between the first shootings in the dorms and the massacre that ensued in the engineering building later that morning?

It is as if we think that if we come up with the right answers we can prevent what happened on Monday morning at Virginia Tech from ever happening again, anywhere. It is what makes us human -- the need to understand, to uncover the pattern that will explain everything, to impose order on anarchy.

In the end, we will never know why Cho Seung-Hui chose to murder students and teachers at Virginia Tech. Surely not by looking for clues in the videos and 1,800-page manifesto he mailed to NBC in the interlude between the first shootings and his final killing spree. In the videos, Cho reads from a script in which he is the victim, and all around him are his persecutors. Cho fancied himself a martyr when he was nothing more than a puerile narcissist.

There has been much discussion of Cho's mental state. A parade of psychologists, psychiatrists and other mental health experts has weighed in to posthumously diagnose Cho as mentally ill. We have learned that he was referred to a psychiatric hospital in Radford, Va., after harassing a female student in 2005. "Affect is flat and mood is depressed," the doctor who evaluated him wrote. "He denies suicidal ideations. He does not acknowledge symptoms of a thought disorder. His insight and judgment are sound," the doctor concluded, ultimately recommending against involuntary commitment.

But blaming the doctor who let Cho go, or even blaming mental illness for what Cho did, it seems to me, is wrong. It is almost as if we have succumbed to Cho's fantasy. He is simply a victim, carrying out an inevitable course of action that others have allowed to happen.

Perhaps it is easier in our postmodern age to ascribe illness to evil. Surely no one in his right mind would do the things that Cho did, we want to believe. But this explanation, like all the others that have been offered to try, even after the fact, to exert some control over what happened, misses the point.

No one is responsible for Cho's deadly deeds but Cho. He carefully planned the carnage he would wreak. He wrote and recorded a script to blame his victims, then mailed it to the media to ensure his own immortality, which most media outlets have been all too eager to accommodate.

There are no larger lessons to learn from this horror, except perhaps that man is capable of almost limitless evil. But after Auschwitz and the Killing Fields of Cambodia, after Jeffrey Dahmer and John Evander Couey, after 9/11 and the suicide bombings that occur almost daily in Iraq, do we still need proof that evil exists?

It would be comforting to think we could stop the Cho Seung-Huis from their deadly mission. If only we had stricter gun laws -- or maybe if we encouraged everyone to carry guns -- we could prevent another Virginia Tech. If only we could better diagnose and treat mental illness -- or else lock up anyone who exhibits violent, antisocial tendencies -- we could ensure no one else would die at the hands of a madman. If only . . .

It is human nature to seek solutions. But the capacity for evil is also a part of human nature. It is something we choose, each of us, of our own free will -- to do good or evil. Cho Seung-Hui chose evil -- and the only bulwark against evil is always to choose good ourselves.