This post first appeared on the Secular Alliance at Indiana University blog.

Why do we punish criminals? We punish as prevention — to keep the criminal from causing further harm, or to deter potential offenders. We punish as rehabilitation — to heal the criminal’s psyche, or to make him a functional member of society. And we punish as retribution — to give the victims peace of mind, or to balance the scales of Justice itself. This is why we lock human beings up in very small rooms with other very bad people, and why we sometimes give money to corrections officers to kill them. But having been made aware that these are our reasons, we can question whether they are good reasons.

Focusing on the death penalty sharpens the question. Given corpses’ incorrigibility, rehabilitation is ruled out. Nor has it been proven that execution is a better deterrent than life in prison. Murderers do not systematically weigh all the consequences before acting. And even if they were rational and well-educated enough to do so, they’d be crazy to give much thought to the death penalty: In the United States, 40% of homicides go unsolved, and even among the convicted, only 3% of murderers are sentenced to be executed.

Now, perhaps if we made the death penalty far more common, we’d start seeing deterrence effects. And maybe we could cut down on the billions of extra dollars we spend on capital trials by cutting a few corners and streamlining the process. (Sure, this might add to the 350+ innocent U.S. citizens who have been wrongfully executed or exonerated at the eleventh hour, but every omelette needs its eggs.) Hell, there are countless changes we could make to more efficiently deter prospective criminals — cut off the hands of serious offenders, torture them horrifically, lock them in solitary confinement for decades. But we have to weigh the benefits of methods like capital punishment against the damage they do — the damage they do to the criminals, and the damage they do to our common humanity, to all members of the society.

This brings us to retribution, the most emotionally compelling justification for executing people. We all intuitively feel that two wrongs do help make a right. If we found a cheap, easy, completely effective way to make murderers productive members of society just by treating them like kings — without inflicting any harm upon them, and with a net benefit for society — it would seem as though our moral cosmos had been turned upside-down. (This is not a thought experiment. Commit your crimes in Norway.) Feeling that an unpunished evil is doubly evil, we try to balance the scales of human suffering — by adding yet more suffering into the mix.

Evolutionarily, our intuitions make some sense. Even if private lethal injections have little value in a modern civil society, we could imagine the fear of murderous reprisals perhaps helping keep prehistoric tribal communities intact. But not all of our evolutionarily ‘natural’ reactions are helpful today. There is nothing more natural in times of human tragedy than wanting to find some enemy or scapegoat to lash out at. Hatred and a lust for death are perfectly normal reactions to grotesque depravity. But such reactions are, for all that, perfectly unhealthy. Finding coherence and closure through positive and constructive endeavors rather than through bloodthirsty vengeance is just as ‘unnatural,’ and just as humanly necessary, as practicing healthy eating in the face of a ‘natural’ instinct to overindulge.

Coping with extreme grief and anxiety by destroying other individuals is a strategy that functioning societies should discourage, not feed. In the rest of the developed world, this is precisely what they do. In the last 10 years, Japan has killed 35 people, Taiwan 41 people, Singapore some unknown large number, and the United States — as of Mr. Steven Wood of Texas, seven days ago — 535 people. Not one of the other 38 developed nations has killed anyone in the 21st century, most having abolished it decades ago. The United States ranks with China, Iran, North Korea, Pakistan, Yemen, Saudi Arabia, Libya, and Syria as one of the few nations in existence retaining a legal system that routinely kills human beings. This on its own does not make the U.S. wrong and the rest of the world right; but it does undermine our confidence that a liberal democracy, to flourish, must execute its citizens.

Do victims need to see other humans suffer in order to find peace of mind? Do we as individuals and as a society function best when we feed our blackest hatred and vindictiveness, or when we undertake the difficult task of cultivating compassion, of humanizing even those we most despise? Only the sciences of mind can hope to find an answer. But in lieu of conclusive evidence, erring on the side of a society held fast by something other than hatred and fear does not seem unreasonable.

It has been argued that capital punishment may actually increase murder rates by sending the “brutalizing” message that it’s acceptable to kill people in some circumstances. Violence begets violence. If it’s OK for a judge or juror or technician or prison official to kill a human being for reasons other than self-defense, the value of a person’s life is not unconditional. So if you think a person is really bad, murder might conceivably be the right thing to do! At least, Mr. Murderer, your goal is vindicated, though we find your methods distasteful (and just might kill you for them). The subtler ramifications of living in a culture that wavers and quibbles on the morality of killing a person surely run far deeper than whatever minute, short-term fluctuations in dehumanization we might be able to detect in the immediate wake of these systematic, targeted, state-sponsored killings.

There is a place in a modern, humane society for preventative and rehabilitative justice. But even if we had any reason to believe that ‘eye for an eye’ morality had a significant deterrent effect, such a benefit would not be worth the price of our humanity. It would not be worth sacrificing the basic and pristine value of every person’s existence. We should draw the line exactly here.