AS FAR AS I can tell, the underlying basis for religion, science and law is the human need for predictability, stability and a hope for certainty. We want to believe that the sun will come up every morning, that if it rains for a long time, it will eventually stop, and that, after a drought, it will eventually rain again.

I think it's also true that we often think change can't occur, within ourselves or in others and institutions. We want things to be different, but we think it's too hard.

The tragedy at Virginia Tech seemed to illustrate both these tendencies. The events were so horrific, and we want to blame everyone . . . but ourselves.

If the parents had raised their child differently, if the public school had intervened earlier, if the university had coordinated the complaints from faculty and students and suspended or expelled Mr. Cho, if the mental-health workers had diagnosed and treated him differently, if gun laws in Virginia hadn't allowed him to buy guns and ammo, if other students could carry guns . . .

If everything had been different, we'd all be safe. Now and forever. Everywhere.

Of course, we can't obtain that level of perfection, at least on earth.

It's possible that earlier intervention might have helped Mr. Cho. Media accounts suggest he displayed elements of pervasive developmental delay (PDD) and schizophrenia. Unfortunately, given his parents' work hours and unfamiliarity with our medical system, it's unlikely that they could have gotten him quality help. If, in fact, they had some sort of health coverage, it is still unlikely that Mr. Cho would have been treated adequately. Most recent studies demonstrate the extreme rarity of childhood schizophrenia, especially under age 12.

The mental-health system generally believes that the onset is in adolescence, so it is often undiagnosed or untreated, even if it's present earlier.

Early-onset disorders are difficult to assess - most children grow out of difficult stages on their own. Each child matures at his own rate. Children don't come into mental health settings on their own; their parents must bring them. Parents, of course, always hope that children will get better on their own.

Also, especially in small families, isolated from a family network, there is little comparison to know what is clearly outside the realm of the normal. And mental-health treatment can't be mandated. People who are irrational or psychotic have the same right to refuse medical treatment as anyone else.

So what CAN change? Society can do better, but it won't be easy - or cheap. Remember when seat belts were first introduced in the 1970s? No one used them - we just sat on them, or disconnected the warning buzzer. But most people now use them as a matter of course, even in a taxi (except, apparently, Gov. Corzine).

Change is hard but not impossible. Those of us who are clinicians deal with this every day - we call it resistance. People come into therapy week after week, month after month, sometimes year after year, wanting their lives to be different - but only magically.

If we truly want to keep our children safe, especially at college, we can't just wait for the administrators. Indeed, many wrote sympathetically to President Steger of Virginia Tech, and to their own campus communities about their commitment to safety. Faculty, staff and students contributed their cell-phone numbers for an emergency response system.

But the fact is, at almost every university, anyone can still walk into any building at any time. It's the rare school that requires any form of ID. At Rutgers in Camden, one of the most dangerous cities in the United States, where I've taught for almost 20 years, the only two non-residential buildings with security systems that require ID are the law school and the library. (Oh, the irony.)

It's true that Mr. Cho had a student ID and would have been able to get in anywhere, but there's no reason why most buildings on campus do not have some system in place, whether a guard or a card swipe, to make some minimal effort to actually increase safety. In an open society, no system is perfect. But that doesn't mean we can't change for the better. *

Ann Rosen Spector is a clinical psychologist in Philadelphia and an adjunct faculty member in the Department of Psychology at Rutgers-Camden.