“Thou shalt not kill” may be the most recognizable moral prohibition in societies around the world.
But where does your sense of justice come from?
Throughout history, justice and laws about wrongdoing have been attributed to one god or another. More recently, justice has been traced to moral truths that can be discovered by judges and other legal experts, and to social norms that vary across cultures.
However, our research instead suggests that the human sense of justice, and criminal laws, is generated by the human brain.
Put simply: Being human makes you a decent lawmaker even if you’ve never stepped foot in law school. To an important extent, criminal laws appear to be the end products of gut feelings about justice that are a part of human nature.
Here’s how we investigated just how universal these intuitions are:
Testing the human brain’s sense of justice
Human conflict ranges from the mild, as when neighbors disagree about the appropriate loudness of music, to the serious, including cases of fraud, robbery, rape, homicide – the stuff of criminal law.
Laws and litigation come in handy when you’re butting heads with someone. But your brain automatically generates intuitions about justice when there is even the potential for conflict, long before you set foot in court. People, even young children, have strong feelings about what counts as a wrongful action and how much punishment a wrongdoer deserves.
These justice intuitions come naturally to everyone. They’re like human lungs or human retinas – part of being human.
So maybe the standard-issue human brain forms the basis of formal and informal justice. If so, a distinctive prediction follows: Laypeople will make decent lawmakers using their sense of justice even when they have no training in law. Further, laypeople will be able to intuitively recreate core features of actual criminal laws from cultures they are totally unfamiliar with.
We devised a study to test those predictions. We showed participants various offenses drawn from actual criminal codes but not the punishments that the law establishes for those offenses.
Some of the offenses we presented came from a modern and culturally familiar society, drawn from Title 18 of the Consolidated Pennsylvania Statutes. But other offenses were truly ancient and culturally foreign. Some participants evaluated offenses from the Laws of Eshnunna, a 3,800-year-old Mesopotamian legal code – one of humanity’s most ancient legal codes. Other participants saw offenses from the Tang Code, a 1,400-year-old legal code from China.
These archaic laws are the next best thing to time travel. They are like fossils that preserve the legal thinking of ancient lawmakers.
To give some examples, some of the Eshnunna offenses shown to participants included: biting out the eye of another man, seizing a boat fraudulently and failing to keep one’s aggressive ox in check, resulting in a slave being killed by the ox. Such were the offenses of an ancient Mesopotamian society.
Despite the massive cultural differences between the ancient city-state of Eshnunna and modern societies, if the sense of justice, and laws, originates in the human brain, then the king who decreed the Laws of Eshnunna and the participants in the study may be of one mind.
So next we asked participants to rate each of the offenses they saw. Some participants were asked to imagine they were lawmakers; they were asked to mock-legislate the fines each offense would deserve by law. Other participants mock-legislated prison sentences for each offense. To make sure participants were giving their untrained intuitions, we excluded from analyses participants who attended law school.
Indeed, the Eshnunna king and the participants in our study did display a shared sense of justice. The more study participants judged an ancient offense as serious, the higher the actual punishment provided by law for that offense.
This match between participants’ intuitions and ancient laws wasn’t perfect, but it was substantial. It suggests that human beings share a sense of justice and that people today can recreate the core of criminal laws from faraway societies that are thousands of years in the past.
Cultural effects on the sense of justice
A shared sense of justice that is part of human nature does not deny cultural differences.
Consider this Tang offense: “All cases of a master who kills a slave who has not committed an offense are punished by one year of penal servitude (NB: redeemable by paying a fine of 20 copper chin).” The Tang Code considers this offense to be relatively mild – consider, for example, that “beating and killing a person in an affray” was punished by the Tang Code with strangulation or a fine of 120 copper chin. In contrast, study participants judged “killing a slave who has not committed an offense” a very serious transgression.
And yet, participants’ intuitive responses generally matched the responses called for in the ancient criminal codes. For instance, participants agreed with the Tang lawmakers that beating and killing a person in a fight is a worse offense than betting goods and articles in games of chance.
To us, this mix of cross-cultural differences and similarities suggests that the brain machinery that generates the sense of justice combines universal principles with open parameters that are filled in with local information. The universal principles may explain why participants generally saw eye to eye with the Eshnunna king and the Tang lawmakers. The open parameters may explain cultural variation.
People, animals, even very simple organisms can be in conflict.
Stan Tekiela Author/Naturalist/Wildlife Photographer/Moment via Getty Images
Evolutionary roots of a sense of justice
Conflict is evolutionarily ancient. Organisms, including nonhuman animals, can offend against others – for example, by preying on them. And so natural selection would have endowed organisms with means that help them solve conflicts in their favor: fangs, antlers, neurotoxic venoms. These defenses and weapons are useful. Our ancestors lived in a world without police, and so they had to be their own police if they were to survive and thrive.
But human conflict is special. With their ingenuity and knack for cooperation, people can produce a huge array of goods and services that other people can swindle, rob, adulterate, counterfeit, embezzle and destroy. So the scope of human conflict is vast.
Brawn may help in human conflict, but brain is key. Humans live in an information-dense world, where it’s important to know precisely how much harm is being done to you when someone offends against you. Accurately appraising wrongs allows victims to demand or deliver an amount of punishment that is, as in the story of Goldilocks, just right: neither too small that an undeterred offender will re-offend, nor too great that the offender will counter-punish the original victim. Our human ancestors didn’t have price tags or written laws to appraise wrongful actions, so they needed to appraise wrongful actions with their brains.
The brain mechanisms for appraising wrongdoing appear to be part of human nature – the same in all times and places humans have lived in. Of course, justice intuitions and criminal laws vary across cultures. Grand theft auto wasn’t appraised in Sparta because there were no cars 2,500 years ago. Written criminal laws are absent in societies without writing systems.
Nevertheless, the human sense of justice seems to be fundamentally similar across space and time. And criminal laws everywhere may be shaped by a sense of justice and offense-appraising mechanisms that are universal – akin to how universal mechanisms of taste perception give rise to the world’s diverse cuisines.
Published on 2022-10-21