Lex talionis, a.k.a “an eye for an eye”: the age-old principle that has us believe that every crime has its fitting punishment, and every wrongdoing a just recompensation. Since Hammurabi’s Code, “retributive justice” – a most oxymoronic coupling, one might say – has worked its way into the justice system and permitted punishments as wide-ranging as incarceration to the death penalty. It has allowed us to quietly nod our heads as society systematically punishes people based on an elaborate system aimed at according a criminal his just dessert.

Central to any retributive punishment, of course, is the premise of moral blameworthiness, which presupposes moral agency and free will. When we fault or punish a person for doing something wrong, we are implicitly saying that the act was committed out of his own volition, of his own free choice.

But the most cursory examination of scientific evidence should give us pause. We now know that when our biology changes, so do our decision-making processes and our desires. The drives we take for granted – be it sexual drive, aggression, motivation for work – depend on intricate workings of our neural circuitry and biological machinery.

Damages to the amygdala, for example, can lead to a constellation of symptoms, including fear, blunting of emotion and overreaction. Frontal disinhibition is known to impair decision-making capacity and repressive personality disorders, causing patients to lose their ability to control impulses. In one study, 57 percent of frontotemporal-dementia patients had sociopathic behavior, compared with only 27 percent of Alzheimer’s patients. The former lacked premeditation and claimed remorse, but did not act on it or express concern for the consequences.

Clinical studies are also contributing evidence that not only are we not free to will, we are not free to won’t. For patients with Tourette’s syndrome, actions occur in the absence of free will. The neural machinery triggers actions that the patient has absolutely no control over. The same applies for people with chorea, and a host of other conditions for which involuntary actions are symptomatic.

It seems that the more we know, the more free will is an illusion. Increasingly, scientific evidence are challenging the very premise of blameworthiness, dissociating moral culpability from the moral agent. If a person cannot help but behave in a way that runs roughshod over societal norms due to biological reasons that we are only beginning to get a handle on, can society reasonably fault him? On what grounds is systematic punishment – ranging from incarceration to capital punishment – justified?

As science reveals more about what drives behavior, “evil”or “ill-will”– and all the words that underscore blameworthiness – are perhaps just words for what we cannot yet explain. As we get better at measuring brain activity, previous behavior that seem inexplicable and human “intent”that were incomprehensible in the past might finally be explainable, even if only partially. Strip away free will and all assumptions of intent, and we come face to face with disease. The dead men walking are not so much “evil” or offsprings of the devil as they are plagued by their own biology. If we believe that, then capital punishment becomes a preposterous notion: Just as we do not kill patients infected with a certain disease, we should not kill criminals no matter how heinous their crimes are. Getting rid of an infected patient, the physician would tell us, does not get rid of the disease.

This is not an argument for the complete elimination of punishment, or moral responsibility per se. After all, different types of punishment serves different purpose, and retribution is not the only reason we punish. But, the evidence we glean from science does pose a challenge to the premise of moral culpability, which we often take for granted in our legal argot and moral reasoning. We are learning that biology and agency are not easily separable, and that we exist along a continuum along every possible axis used to measure human beings.

This presents some thorny problems for the judge. Supposing all conditions relating to the situation of a crime are held equal, should person A and person B (which we must reasonably assume to be different along some axis) be ascribed equal culpability and hence receive the same punishment? Certainly the current legal system, at least in principle, does so in the name of equality before the law. But if we’re really the unequal oddballs that we are, the question that hangs in the air is: should it?

As always, the leap from the is to the ought is never an easy one to make, but my sense is that retributive justice or the idea of “just dessert” deserves way less currency than it has now. In place of retribution should be a focus on rehabilitation or recidivism reduction. This calls for more science, innovation and more experimental approaches to figure out, to that end, what works and what doesn’t. For whatever emotional satisfaction that retributive punishment might bring for the punisher or victim, there is nevertheless no “justice” to be had through retribution.

The lesson we’re taught in pre-school sandboxes still rings true: an eye for an eye makes the world go blind.

Contact Chi Ling, Chan at chiling ‘at’ stanford.edu.