by Mark Costanzo

About the author: Mark Costanzo is the author of Just Revenge,from which this viewpoint is excerpted.

When faced with compelling evidence that the death penalty is costly, arbitrary, discriminatory, prone to error, and without deterrent value, retentionists often retreat into the murky waters of moral philosophy. They argue that capital punishment is not only morally legitimate, but also morally necessary. Although we can decide questions of fact—questions about cost, deterrence, fairness, and public opinion—by analyzing the relevant data, the question of whether the death penalty is ethically justified cannot be answered by any amount of data. It is a matter of faith and argument. And that is precisely why many supporters of the death penalty would prefer to debate philosophy instead of effectiveness. If we are morally compelled to kill those...