Police in Newport News, Virginia, were weary of answering calls about burglars and drug dealers in a rundown housing project. Finally, the project was scheduled for demolition, and in preparation for the new construction, police decided to clean up the area: They carted away trash, removed abandoned cars, filled in potholes.

To everyone's surprise, as soon as the housecleaning began, burglary rates dropped 35 percent. The police department had inadvertently stumbled on a fresh approach to crime—a formula that is being adopted around the country under the rubric of community policing. Instead of waiting for crimes to occur, police are addressing problems that often attract crime: general disorder and decay.

Supporters of the new philosophy may not know it, but they are reviving a classic Christian understanding that crime is not only an individual act but also a violation of the social order. Hence, one of the best ways to fight crime is to restore order.

Not long ago, New York City's Precinct 75 was one of the most dangerous places in America. Then the NYPD decided to show zero tolerance for any violation of public order. Officers stopped all traffic violators (which often led to finding drugs and guns). They chased away loiterers (who often turned out to be drug dealers looking for a sale). In three years, homicides dropped from 126 to 47.

After a gunfight in a Baltimore housing project, police worked with local agencies to upgrade street lighting, trim shrubbery, clean alleys, build a playground. Burglaries were reduced 80 percent, auto larceny 100 percent.

These success stories illustrated what criminologist James Q. Wilson calls the broken-window theory. Sociologists have discovered that if a window in a building is ...