UNTIL THE FULL psychological autopsy is available, we do not have all the data with which to understand the Virginia Tech massacre, the worst mass shooting so far in the U.S. It is common in such conditions to assume that we will never be able to understand such a terrible thing. A former FBI profiler said in one of the TV accounts that “we’re never going to know why he did it,” referring to the killer, Cho Seung-Hui.

That kind of fatalism dashes the hopes of scientists who believe that, at least in principle, one can understand anything. We need a spirit of optimism with regard to understanding human nature in all of its manifestations.

As we grieve and ponder, we must not let ourselves think that the worst of human behavior and the grief it can cause are beyond understanding. On the contrary, we must know what happened. There are many pathways to normal adulthood and acceptable individual differences. The stray instances, however, are of immense consequence for families and society. We must be able to capitalize on the power of interventions with the severely affected and dangerous.

More young people die of behavioral misadventures like suicide, homicide and accidents than of all diseases combined. The Virginia incident is an example giving this truth the edge. One young man’s horrendous behavior has taken the lives of 32 others and then his own. While the relevant behavior is principally that of the killer, this is not to say that nobody else’s behavior mattered. The killings occurred in an environment in which bright people — some of them brilliant thinkers — lived and worked. This individual had been seen by many, including top-level mental-health experts, as dangerous and in need of counseling, hospitalization, and police interference.

Recognizing someone with extremely aberrant self-regulatory behavior, including the potential for harm, is possible, and there is already evidence that this young man’s behavior was sufficiently off the curve for a long time, and that many people knew about it.

This massacre developed; it didn’t just happen.

The behavior of the Virginia murderer had causes. This does not excuse it, or make the day less tragic, or make him less evil. But we must not treat it as an event that just could not have been avoided. It is not enough to say he was mentally ill. Mental illness has causes. It is not enough to say he should not have stopped taking the medications prescribed for him, if indeed he did. That too easily lets the environment off the hook, and gives a lame excuse for avoiding the hard science of human development yet to be done in this instance and for all time.

Detection of individuals intending harm has its own perils. Attempts to track and report aberrant behaviors of others can result in the blanket being cast too broadly. Individuals may be falsely identified, with their reputations possibly damaged irreparably. Harmless individuals can have their lives seriously handicapped. This is another reason the scientific job must be done well. We need reliable means of detecting dangerous people, for their own and the public good. We need to be able to do this without hurting people who are merely different. This will be important to the preservation and freedom of college campuses, as well as the country in general.

We need to understand the depth of the human spirit in all of its manifestations, evil and virtuous, deplorable and heroic. That will take a much greater investment than has ever been made in the science of human behavior and its development.

The human animal can be more destructive of its own species and its living environment than any other animal. It seems to go with the territory. As the 19th Century British essayist William Hazlitt said, man is the only animal that laughs and cries, for we are the only species that knows the difference between the way things are and the way they could be.

Lewis P. Lipsitt is a professor emeritus of psychology, medical science, and human development at Brown University.