[Excerpt] The Tragedy of Commonsense Morality

Part Of: Demystifying Ethics sequence
Content Summary: 1500 words, 15 min read.

Excerpts are not my writing! This comes from Joshua Greene’s excellent book:

Moral Tribes: Emotion, Reason, and the Gap between Us and Them

The book goes on to present an interesting solution to the below problem. Check it out!

The Tragedy of the Commons

The following parable – entitled tragedy of the commons – originates from Garrett Hardin’s 1968 paper:

A single group of herders shares a common pasture. The commons is large enough to support many animals, but not infinitely many. From time to time, each herder must decide whether to add another animal to her flock. What’s a rational herder to do? By adding an animal to her herd, she receives a substantial benefit when she sells the animal at market. However, the cost of supporting that animal is shared by all who use the commons. Thus, the herder gains a lot, but pays only a little, by adding an additional animal to her herd. Therefore, she is best served by increasing the size of her herd indefinitely, so long as the commons remains available. Of course, every other herder has the same set of incentives. If each herder acts according to her self-interest, the commons will be completely eroded, and there will be nothing left for anyone.

You may recognize the economic structure of this game from the Prisoner’s Dilemma. To win such a game, you must find the magic corner; that is, to accomplish cooperative outcomes despite the temptation of selfishness.

The problem of cooperation is the central problem of social existence. Fortunately, our brains come equipped with the following mechanisms, all of which foster cooperation.

  1. Concern for others. Two prisoners can find the magic corner if they place some value on each other’s payoffs in addition to their own.
    • Faculties: empathy, violence aversion.
  2. Direct reciprocity. Two prisoners can find the magic corner if they know that being uncooperative now will deny the benefits of future cooperation.
    • Faculties: punitive motivation, forgiveness, gratitude
  3. Commitments. Two prisoners can find the magic corner if they are committed to punishing each other’s uncooperative behavior.
    • Faculties: shame, guilt, loyalty.
  4. Reputation. Two prisoners can find the magic corner if they know that being uncooperative now will deny us the benefits of future cooperation with others.
    • Faculties: gossip, embarrassment.
  5. Assortment. Two prisoners can find the magic corner by belonging to a cooperative group, provided that group members can reliably identify one another.
    • Faculties: identity markers, tribalism

We have cooperative brains, it seems, because cooperation provides material benefits, biological resources that enable our genes to make more copies of ourselves. Out of evolutionary dirt grows the flower of human goodness.

The Tragedy of Common Sense Morality

To the east of a deep, dark forest, a tribe of herder raise sheep on a common pasture. Here the rule is simple: each family gets the same number of sheep. Families send representatives to a council of elders, which governs the commons. Over the years, the council has made difficult decisions. One family, for example, took to breeding exceptionally large sheep, thus appropriating more of the commons for itself. After some heated debate, the council put a stop to this. Another family was caught poisoning its neighbors’ sheep. For this the family was severely punished. Some said too severely. Others said not enough. Despite these challenges, the Eastern tribe has survived, and its families have prospered, some more than others.

To the west of the forest is another tribe whose herders also share a common pasture. There, however, the size of a family’s flock is determined by the family’s size. Here, too, there is a council of elders, which has made difficult decisions. One particularly fertile family had twelve children, far more than the rest. Some complained that they were taking  up too much of the commons. A different family fell ill, losing five of their six children in one year. Some thought it was unfair to compound their tragedy by reducing their wealth by more than half. Despite these challenges, the Western tribe has survived, and its families have prospered, some more than others.

To the north of the forest is yet another tribe. Here there is no common pasture. Each family has its own plot of land, surrounded by a fence. These plots vary greatly in size and fertility. This is partly because some Northern herders are wiser and more industrious than others. Many such herders have expanded their lands, using their surpluses to buy land from their less prosperous neighbors. Some Northern herders are less prosperous than others simply because they are unlucky, having lost their flock or their children to disease. Still other herders are exceptionally lucky, possessing large fertile plots of land, not because they are especially industrious but because they inherited them. Here in the North, the council of elders doesn’t do much. They simply ensure that herders keep their promises and respect one another’s property. The vast differences in wealth among Northern families has been the source of much strife. Each year, some Northerners die in winter for want of food and warmth. Despite these challenges, the Northern tribe has survived, and its families have prospered, some more than others.

To the south of the forest is a fourth tribe. They share not only their pasture but their animals, too. Their council of elders is very busy. The elders manage the tribe’s herd, assign people to jobs, and monitor their work. The fruits of this tribe’s labor are shared equally among all its members. This is a source of much strife, as some tribe members are wiser and more industrious than others. The council hears many complaints about lazy workers. Most members, however, work hard. Some are moved to work by community spirit, others by fear of their neighbor’s reproach. Despite these challenges, the Southern tribe has survived. Its families are not, on average, as prosperous as those in the North, but they do well enough, and in the South no one has ever died in winter for want of food or warmth.  

One summer, a great fire burned through the forest, reducing it to ash. Then came heavy rains, and before long the land, once thick with trees, was transformed into an expanse of gently rolling grassy hills, perfect for grazing animals. The nearby tribes rushed in to claim the land. This was a source of much strife. The Southern tribe proclaimed that the new pastures belonged to all people and must be worked in common. They formed a new council to manage the new pastures and invited the other tribes to send representatives. The Northern herders scoffed at this suggestion. While the Southerners were making their big plans, Northern families built houses and stone walls and set their animals to graze. Many Easterners and Westerners did the same, though with less vigor. Some families sent representatives to the new council.

The four tribes fought bitterly, and many lives, both human and animal were lost. Small quarrels turned into bloody feuds, which turned into deadly battles. A Southern sheep slipped into a Northerner’s field. The Northerner demanded a fee to return it. The Southerners refused to pay. The Northerner slaughtered the sheep. The Southerners took three of the Northerner’s sheep and slaughtered them. The Northerners took ten of the Southerner’s sheep and slaughtered them. The Southerners burned down the Northerners farmhouse, killing a child. Ten Northern families marched on the Southerner’s meeting house and set it ablaze, killing dozens of Southerners, including many children. Back and forth they went with violence and vengeance, soaking the green hills with blood.

The tribes of the new pastures are engaged in bitter, often bloody conflict, even though they are all, in their different ways, moral peoples. They fight not because they are fundamentally selfish but because they have incompatible visions of what a moral society should be. These are not mere scholarly disagreements, although their scholars have those, too. Rather, each tribe’s philosophy is woven into its daily life. Each tribe has its own version of moral common sense. The tribes of the new pastures fight not because they are immoral but because they view life on the new pastures from very different moral perspectives. I call this the Tragedy of Commonsense Morality.

Five psychological tendencies tend to exacerbate intertribal conflict:

  1. Naked group selfishness. Human tribes are tribalistic, favoring Us over Them.
  2. Moral disagreement. Tribes have genuine disagreements about how societies should be organized, with different emphases on e.g., the rights of individuals versus the greater good.
  3. Authority question begging. Tribes have distinctive moral commitments, whereby moral authority is vested in local individuals, texts, traditions and deities that other groups don’t recognize as authoritative.
  4. Asymmetry capitalization. Tribes are prone to biased fairness, allowing group-level self-interest to distort their sense of justice
  5. Punitive escalation. The way we process information about social events can cause us to underestimate the harm we cause others, leading to the escalation of conflict.

Morality is nature’s solution to the Tragedy of the Commons, enabling us to put Us ahead of Me. But nature has no ready-made solution to the Tragedy of Commonsense Morality, the problem of enabling Us to get along with Them. And therein lies our problem. If we are to avert the Tragedy of Commonsense Morality, we’re going to have to find our own, unnatural solution: what I’ve called a metamorality, a higher-level moral system that adjudicates among competing tribal moralities, just as a tribe’s morality adjudicates among competing individuals.


A Dual-Process Theory of Moral Judgment

Part Of: Demystifying Ethics sequence
Content Summary: 900 words, 9 min read


An ethical theory is an attempt to explain what goodness is: to ground ethics in some feature of the world. We have discussed five such theories, including:

  • Consequentialism, which claims that goodness stems from the consequences of an action
  • Deontology, which claims that goodness stems from absolute obligations (discoverable in light of the categorical imperative)

For most behaviors (e.g., theft), both theories agree (in this case, label the act as Evil). But there do exist key scenarios which prompt these theories to disagree. Consider the switch dilemma:

Consider a trolley barreling down a track that will kill five people unless diverted. However, on the other track a single person has been similarly demobilized. Should you pull to lever to divert the trolley?

Ethical Theories- Trolley Problem (2)

Our ethical theories produce the following advice:

  • Consequentialism says: pull the lever! One death is awful, but better than five.
  • Deontology says: don’t pull the lever! Any action that takes innocent life is wrong. The five deaths are awful, but not your fault.

Would you pull the lever? Good people disagree. However, if you are like most people, you will probably say “yes”. 

Things get interesting if we modify the problem as follows. Consider the footbridge dilemma:

Consider a trolley barreling down a track that will kill five people unless diverted. You are standing on a bridge with a fat man. If you push the fat man onto the track, the trolley will derail, sparing the five people.

Dual Process Morality- Trolley Visceral Alternative (1)

Notice that the consequences for the action remain the same. Thus, consequentialism says “push the fat man!”, and deontology says “don’t push!”

What about you? Would you push the fat man? Good people disagree; however, most people confess they would not push the fat man off the bridge. 

Dual Process Morality- Conflicting Judgments (1)

Our contrasting intuitions are quite puzzling. After all, they only thing that’s different between the two cases is how close the violence is: far away (switch) vs up close (shoving).

Towards a Dual-Process Theory

Recall that there are two kinds of ethical theories.

  1. Prescriptive theories describe what goodness objectively is.
  2. Descriptive theories tell us how the brain produces moral judgments.

Consequentialism and deontology are prescriptive theories. However, we can also conceive of consequentialism and deontology as descriptive theories. Let’s call these descriptive variants folk consequentialism and folk deontology, respectively.

Sometimes, people’s judgments is better explained by folk consequentialism; other times, folk deontology enjoys more predictive success. We might entertain two hypotheses to explain this divergence:

  1. Different boundary conditions of a single neural process
  2. Two competing processes for moral judgment

As we will see, the evidence suggests that the second hypothesis, the dual-process theory of moral judgment, is correct.

Dissociation-Based Evidence

Consider the crying baby dilemma:

It’s wartime. You and your fellow villagers are hiding from nearby enemy soldiers in a basement. Your baby starts to cry, and you cover your baby’s mouth to block the sound. If you remove your hand, your baby will cry loudly, and the soldiers will hear. They will find you… and they will kill all of your. If you do not remove your hand, your baby will smother to death. Is it morally acceptable to smother your baby to death in order to save yourself and the other villagers?

Here, people take a long time to answer, and show no consensus in their answers. If the dual-process theory of moral judgment is correct, then we expect the following:

  1. Everyone exhibits increased activity in the dorsal anterior cingulate (dACC). This region is known to reliably respond when two or more incompatible behavioral responses are simultaneously activated. 
  2. For those who eventually choose the folk consequentialist answer (save the most lives) should exhibit comparatively more activity in brain regions associated with working memory and cognitive control.

Both predictions turn out to be true. Here then is the circuit diagram of our dual-process, organized in the two cybernetic loops framework:

Dual-Process Morality- System Architecture

Four other streams of evidence corroborate our dual-process theory:

  • Deontological judgments are produced more quickly than consequentialist ones.
  • Cognitive distractions slow down consequentialist but not deontological judgments.
  • Patients with dementia or lesions that cause “emotional blunting” are disproportionately likely to approve of consequentialist action. 
  • People who are either high in “need for cognition” and low in “faith in intuition”, or have unusually high working memory capacity, tend to produce more consequentialist judgments.

Relation To Other Disciplines

We have previously distinguished two kinds of moral machinery:

  • Propriety frames are a memory format that retains social intuitions.
  • Social intuition generators which contribute to the contents of social judgments.

These machines map to the dual-process theory of judgment. Propriety frames are housed in cerebral cortex, which perform folk consequentialist analysis. Social intuition generators are located within the limbic system, and contribute folk deontology intuitions.

Recall that Kantian deontology attempted to ground moral facts in pure reason (the categorical imperative). While surely valuable as a philosophical exercise, in practice folk deontological judgments have little to do with reason. They are instead driven by autonomic emotional responses. It is folk consequential judgments which depend more on reason (cortical reasoning).

This is not to say that people who prefer consequential reasoning are strictly superior moral judges. But I will address the question which reasoning system should I trust more? on another day.


  • For the switch dilemma, most people reason consequentially (“save the most lives”)
  • For the footbridge dilemma, most people reason deontologically (“murder is always wrong”)
  • These contrasting styles emerge because the brain has two systems of judgment.
  • Folk consequentist reasoning is performed in cerebral cortex.
  • Folk deontology intuitions are generated from within the limbic system.

Until next time.