NO ONE ARGUES that those who commit particularly outrageous crimes, such as murder, should be allowed to walk freely among the general population. Punishment for violating the rules that enable people to live together is a necessary part of any human society. The nature of that punishment—what form it takes and how severe it should be—is cause for a great deal of debate, especially with a crime as terrible as murder.

Debate over capital punishment often involves practical considerations, such as whether the death penalty deters brutal crimes, and legal considerations, such as whether the laws as written can assure fairness. At some point, though, talk usually turns to questions of morality. Although many individuals feel strongly that capital punishment is either moral or immoral, Americans as a group have not decided...