In its most extreme forms, aggression is human tragedy unsurpassed. Hopes that the horrors of World War II and the Holocaust would produce a worldwide revulsion against the taking of another human's life, resulting in the end of genocidal practices and a reduction in homicide rates, have been dashed by the realities of increasing homicide and genocide in the last half of the twentieth century. The litany of genocidal events is both long and depressing, including major massacres in Uganda, Cambodia, Rwanda, Burundi, Zaire, Bosnia, Serbia, Croatia, and Herzegovina, among others. Homicide rates have risen in a number of industrialized countries since World War II, most notably in the United States.

We have seen slight declines in the homicide rate in the United States during the 1990s. But despite six consecutive years of decreases, the 1997 homicide rate was still 133 percent of the 1965 rate, and 166 percent of the 1955 rate...