When someone unleashes a seemingly incomprehensible amount of rage upon innocent civilians – as seen in the recent Virginia Tech killings – there is one question everyone seems to ask: “What would motivate someone to do such a thing.” The problem is that this question often leads people to try to “de-motivate” criminals, which is simply not a realistic objective.

After focusing for nearly 100 years on the unrealistic task of de-motivating the offender, the field of criminology was given a reprieve in 1979 when Lawrence Cohen and Marcus Felson developed the “Routine Activities” theory of crime. This theory shifted the emphasis from the motivated offender to a) the suitable target of crime, and b) the capable guardian against crime.

Cohen and Felson assumed that in any society at any time there would be no shortage of people “motivated” to commit crimes. By treating the “motivated offender” as a constant they were shifting emphasis to two variables, which can vary wildly across time and geographical location. And they also provide the best explanation for the necessity of firearms ownership by responsible citizens.

Since the “suitable target” and “capable guardian” concepts are undoubtedly unfamiliar to most readers, I would suggest that we indulge in a creative exercise. It starts with the reader imagining he is a motivated offender – specifically, one who is motivated to commit the crime of burglary in a typical residential neighborhood in the year 1957.

If you take a few minutes to imagine you are “casing” a residence – that is, looking inside before entering – you will notice something interesting: There are few suitable targets inside.

All of the valuables inside the average 1950s home were simply too bulky for the average burglar to steal by himself. The television (there was probably only one), the radio, and the stereo system (probably a turntable connected to a receiver and two big speakers) were all many times heavier than they are today.

But there is something else the would-be 1957 burglar would see upon looking in the house: A housewife, or, in other words, a capable guardian.

Imagine further that due to the absence of suitable (i.e., light and expensive) targets and the presence of the capable guardian you delay your burglary attempt until 2007, though your motivation has never waned.

In the process of “casing” the average 2007 home, you see something very different. The television (now there are several), radio, and stereo got a whole lot lighter. And there are all kinds of new, light, portable, and expensive goodies to steal (laptops, DVD players, iPods, etc.). They all go by the same name: Suitable targets.

And, of course, you probably notice something else: Mrs. Cunningham isn’t home. In other words, there is no capable guardian standing in your way.

Property crimes have not increased dramatically in the last 50 years because of some magic increase in the number of evil people who are motivated to commit crimes like burglary. The motivated offenders have always been there. It’s just easier today to do what they have always wanted to do.

The story is no different with regard to violent crime. Today, we live in a society that is more densely populated than it was fifty years ago. Furthermore, the percentage of people living in urban as opposed to rural areas has dramatically increased. That means the motivated rapist (or murderer or mugger) has access to more suitable targets than ever before.

And, needless to say, the fact that people delay marriage and frequent bars and shopping malls in greater number means they are in greater peril. While the number of suitable targets has been rising, capable guardians have been disappearing.

Our nation’s colleges have long been a safe haven for criminals because they are areas with a heavy concentration of suitable targets for violent crime. The campuses keep growing as a larger percentage of the population now sees the necessity of getting a college education. And the freshmen classes who are getting away from the guardianship of mom and dad for the first time are classes mostly comprised of young women.

The University of Utah is one of a minority of schools that realizes there is one way to turn suitable targets into unsuitable targets for violence: Let them carry guns on campus. And other schools like The University of South Carolina and other colleges in that state may soon follow suit.

City College of San Francisco, on the other hand, is taking a different approach. They not only plan to keep their students unarmed but also their campus police. In fact, the school recently lost a police chief who resigned in frustration after someone stormed the campus threatening to kill innocent students. The man was arrested but only after campus police called in reinforcements from the City of San Francisco.

City College of San Francisco has every right to expend time and resources on teaching and research activity that seeks to understand and reduce the motivation of those who seek to harm us. They may ask the question “why do killers hate us?” They may even seek to sooth the killer’s inner child.

But the motivation to harm others can never be extinguished from the depths of the human soul. One can only keep the harmful at a safe distance with a loaded gun.