Science is intended to discover the “is”, not the “ought;” facts, not values. Science can’t tell us whether an action is moral; it can only provide evidence to help inform moral decisions. For instance, some people who believe abortion is immoral reject birth control methods that prevent implantation of a fertilized ovum on the grounds that it constitutes abortion; science can determine that a particular birth control method prevents fertilization rather than preventing implantation of a fertilized ovum. A new book, Moral Tribes: Emotion, Reason, and the Gap Between Us and Them, by Joshua Greene, provides some intriguing insights that are pertinent to medical ethics.

He thinks tribalism is the central tragedy of modern life. Evolution equipped us for cooperation within our own tribe but not for cooperation with other tribes. Cooperation with related individuals helps spread our own genes, but we are in competition with other tribes and cooperating with them might help spread their genes to the detriment of our own. It boils down to Us vs. Me and Us vs. Them. He uses the word “tribes” not in the original sense (Hutus vs. Tutsis), but to include Democrats vs. Republicans, Catholics vs. Protestants, CAM vs. science-based medicine, Arabs vs. Israelis, climate change activists vs. climate change deniers, and any other ideological or nationalistic group.

He says morality is not what generations of philosophers and theologians have assumed. It is not a set of freestanding abstract truths, but rather a manifestation of moral psychology.

  • Morality is a suite of psychological capacities designed by biological and cultural evolution to promote cooperation.
  • It is implemented through emotional moral intuitions, gut reactions that cause us to value the interests of (some) others.
  • Different human groups have different moral intuitions, resulting in conflict.

Opponents of abortion feel strongly that it is always “wrong” to destroy a fetus. Proponents of abortion feel just as strongly that it is always “wrong” to interfere with a woman’s control of her own body. Their positions are incompatible, and they are unable to agree on a policy that will satisfy both tribes. Greene thinks we can only make progress if we understand what morality is, how it got here, and how it’s implemented in our brains. He describes recent studies in experimental psychology and cognitive neuroscience that can help us understand.


The science of “trolleyology” investigates the role of emotions in morality. The basic trolley scenario: a trolley is headed down the track towards 5 people, and will kill those people unless you throw a switch and send it down another track where it will only kill one person. Most people agree that it is better to throw the switch; but if the choice is to stop the trolley by pushing a person off a footbridge onto the track, most people wouldn’t do it. The math is the same: sacrificing one life to save five. But most people who are not psychopaths have a strong emotional reaction that makes them feel it is more immoral to actively push someone than to throw a switch. This is a gut reaction that doesn’t involve reasoning. But what if the person you push is a rapist and murderer? What if the one person killed by switching tracks is your child? Variations on the trolley theme are a good tool for investigating how our brains work.

We have dual-process brains

We have dual-process brains: we react automatically, but we can also think things through deliberately. The automatic mode allows us to react quickly and appropriately to danger (see lion, run); the manual mode allows us to weigh the consequences of our actions and defer temporary pleasures for long-term gain (stopping to eat berries vs. continuing to follow the trail of a mastodon that you can kill to feed the whole tribe.) A gizmo in our brains responds negatively to violent acts, regardless of whatever benefits they may produce. It also gives us a taste for punishing others when they act unfairly and makes us far more concerned about the plight of people who are present than about the plight of those who are far away. The gizmo has an important function; but we should recognize that while our moral intuitions are generally sensible, they not infallible.

Greene compares the brain to a camera with general-purpose automatic settings that can be over-ridden to customize the settings for specific purposes. Emotions serve as heuristics, mental shortcuts that we use to make decisions. They allow rapid, efficient action that is generally adaptive. Reason can free us from the tyranny of emotion, but it can’t produce the best decisions without some emotional input. Think Mr. Spock and Capt. Kirk. Emotions that are not tempered by reason can lead to irrational mistakes; both our perceptions and our sense of fairness are biased. Selfishness can be overcome by our automatic settings for the benefit of the tribe; moral inflexibility in the face of another morally inflexible tribe can only be overcome by shifting into manual mode.

Facts are not enough

We like to think that if people are given the facts and have critical thinking skills, they will recognize the truth about climate change, vaccination, etc. Not true. People who are more scientifically literate are more adept at defending their tribe’s beliefs, whether they are true or not. Ordinary people are hopeless slaves to tribal prejudice. People are willing to consult experts about most things, but expert consensus means nothing once a false belief has been culturally entrenched and has become a tribal badge of honor. Experts agree on climate change, but there’s widespread disagreement among the public. Egalitarian communitarians accept the scientists’ consensus of great risk and the need for collective action; hierarchical individualists trust their own tribe’s chosen high-status authorities and are wary of collective actions.

Many of our debates hinge on standard value premises of security vs. freedom. This becomes crystal clear in discussions of vaccines. Pro-vaccinationists value the security of eliminating preventable diseases for everyone; anti-vaccinationists value the freedom to make individual decisions and to put what they perceive to be their own personal interests above the interests of herd immunity.

Political divisions often boil down to individualism vs. collectivism. Should everyone pay the same flat income tax, or should the rich pay more than the poor? One side thinks the individual should reap the rewards of his own hard work and believes it is unfair to take goods from him and give to others who have not earned them. The other side thinks justice requires the more fortunate to share with the less fortunate. Both sides are more committed to their ways of life than to producing good results. Their values are not about “whatever works” but about deep moral truths.

Harms caused by action vs. harms of omission

We instinctively feel that harms caused by actions are worse than harms of omission. This can be debunked. Our brains can’t keep track of all the things we are NOT doing. The brain considers actions and omissions in fundamentally different ways, and actions are more accessible to our minds. The AMA distinguishes intentional euthanasia (forbidden) from providing drugs to relieve pain that also happen to end a patient’s life. Under the AMA Doctrine of Double Effect and the Doctrine of Doing and Allowing, terminally ill patients may not get what’s best and what they want for themselves. Our automatic gizmo creates opposition to physician-assisted suicide, mandatory vaccination, and policies surrounding organ donation and abortion.

We are working against 6 psychological tendencies

  1. Human tribalism favors Us over Them
  2. Tribes place different emphasis on rights of individuals vs. good of the group
  3. Different groups follow different moral authorities, often religious
  4. Biased fairness – group self-interest distorts sense of justice
  5. Biased beliefs – from self-interest and social dynamics
  6. We tend to underestimate the harm we cause others

Is utilitarianism the solution?

Greene thinks an enlightened utilitarianism is the answer: we should do whatever will produce the best overall consequences for all concerned. Caution is required, because it’s easy to fool ourselves into thinking that what we want serves the greater good. Some might argue that slavery could be an overall good if the advantages to the slave owners outweigh the harm to the slaves. It’s easy to show that belief to be false by simply asking whether they would agree to live half their life as slaves in order to reap the benefits of being a slave owner during the other half of their lives, especially if the order of events is randomly chosen and there is no guarantee of humane treatment for slaves. In principle you might be able to maximize happiness by oppressing some people, but in the real world oppression does not make the world a happier place. “In the real world, there is no fundamental tension between happiness and justice.”

Greene argues for Mill’s “higher pleasures.” Things like getting drunk or overeating are temporary pleasures that don’t benefit the individual in the long run; higher pleasures like the gratifications of learning are often those that also build durable and shareable resources. Our instincts serve us well to confront the moral temptations of everyday life (matters of Me vs. Us): they will stop us from hurting a neighbor by lying, stealing from him, or killing him. But when it’s a matter of Us vs. Them our instincts are not reliable and we should resort to explicit thinking about the greater good.

Three approaches to moral truth that fail:

  1. Religion: relies on personal revelation not accessible to all; relies on different interpretations of God’s will.
  2. Reason: founded on axioms. After centuries of trying, no one has found a serviceable set of moral axioms that are (a) self-evidently true and (b) can be used to derive conclusions that settle real-world moral disagreements. Reason can make our moral opinions more consistent, but it can’t tell us how to make trade-offs between competing values of different moral tribes.
  3. Science: fails on the “is/ought” level. Evolution can explain how morality evolved to promote cooperation within groups for the sake of competition between groups. Our genes might be better spread by killing all the other tribe than by cooperating with them. The axiom “what’s right is what fulfills the purpose for which morality evolved” is not self-evidently true. Cooperation is not the ultimate moral good: it can result in misery for those who cooperate. The Borg is highly cooperative but isn’t much fun, and most of us would not choose to join. Cooperation is not an end in itself, but is valuable because of the happiness and relief from suffering that it brings.


Greene quotes Barack Obama:

Democracy demands that the religiously motivated translate their concerns into universal, rather than religion-specific, values. It requires that their proposals be subject to argument, and amenable to reason. I may be opposed to abortion for religious reasons, but if I seek to pass a law banning the practice, I cannot simply point to the teachings of my church or [invoke] God’s will. I have to explain why abortion violates some principle that is accessible to people of all faiths, including those with no faith at all.

Abortion debate boils down to strong but complicated feelings that we can neither justify nor ignore. But we can ask questions about consequences. What impact do policies have on our lives? What happens if legal access to abortion is restricted?

If abortion is illegal, it removes an important safety net from millions of people, it tends to interfere with the enjoyment of sex, it causes people to seek illegal abortions at great expense or risk, it forces women to endure the discomforts and health risks of pregnancy against their will, it disrupts life plans, it tends to remove women from the work force, and it even costs lives (the death rate from pregnancy is higher than from therapeutic abortion). There’s no good argument against abortion except that it would grant life to people who wouldn’t otherwise exist. Those who are concerned about overpopulation would disagree that that was a good thing; and even for those who agree, this argument is TOO good: if it is valid, it should also apply to all forms of contraception and nonreproductive sex. Remember Monty Python’s “Every Sperm is Sacred.” In an unbiased assessment of the consequences, pro-choice wins, although it still hasn’t determined where to draw the line. If you go by fetal viability, the line changes as technology improves. Any line is arbitrary, but it could always be adjusted based on good evidence of harms vs. benefits. If our gut reaction is that early abortion is OK but 3rd trimester is not, we can look for a moral theory to match our feelings, but gut reactions were not designed to be organized, and they weren’t necessarily designed to serve truly moral ends.

Our reasons are confabulations

Science shows that most of the reasons we give are confabulations to rationalize preferences. People primed with words like ocean-moon were more likely to choose Tide detergent, but gave reasons like “Mom used it” or “I liked the box”. We constantly interpret our own behavior, building a plausible narrative about what we are doing and why. We rationalize to justify the emotionally-compelling moral dictates of our automatic settings.

Death penalty proponents and opponents cite evidence that it does or doesn’t reduce crime, but if they are proven wrong they fall back on “It’s still wrong on principle” or “It’s the moral right of an aggrieved society.” Heads I win, tails you lose.

Claims about what will promote the greater good (whether the death penalty will reduce crime, whether a policy will increase or decrease the total happiness of society) can be supported by evidence; claims about “rights” are oblivious to evidence.

People think they understand how things like zippers and toilets work but when asked to explain them, they realize that they don’t really know. In a brilliant set of experiments, people were asked about policy proposals like single-payer healthcare systems. Those who opposed a proposal were asked to explain the details of how it would work and were forced to realize they really didn’t fully understand it; this realization changed their attitudes and made them less opposed. People who were just asked for reasons for their opinion didn’t change. And we know that people whose reasons are challenged only become more convinced they are right. So forcing people to confront their ignorance of essential facts may be a way to make them more moderate. I wonder if it would help to ask anti-vaccine activists to explain how vaccines are developed and how they work?

Pragmatic utilitarianism as a solution to conflicts?

The first step to agreement is to concede that your opponents are not evil and hold their beliefs and values as strongly as you do yours. People are all basically alike. To me, I’m special; to them, they’re special too.

The next step is to set aside gut reactions and look objectively at consequences. We can capitalize on the values we share and seek a common currency there. The Golden Rule is generally accepted by everyone. Science also offers a common currency. Tribes may believe earthquakes are caused by the thrashing of giant catfish or the earth’s shivering when it is ill; such myths vary and contradict each other. But science is the same everywhere and we all ought to be able to agree that a scientific explanation based on plate tectonics is preferable to unsubstantiated myths.

How should we think about the foolish man who refused to buy health insurance? Is healthcare a right or a product? We can use manual-mode thinking to reach agreements with our “heads” rather than our “hearts” – to yield a moral philosophy that no one loves but that everyone “gets” – to acquire a second moral language that members of all tribes can speak. We can acknowledge that:

taking a bit of money from the haves hurts them very little, while providing resources and opportunities to the have-nots, when done wisely, goes a long way. That’s not socialism. That’s deep pragmatism.

Greene says:

Utilitarianism asks only that we push ourselves to be morally better, to care more than we do about people beyond our immediate circles. Utilitarianism doesn’t ask us to be morally perfect. It asks us to face up to our moral limitations and do as much as we humanly can to overcome them. Here science can help, showing us just how fickle and irrational our sense of duty can be.

This fits well with Michael Shermer’s hierarchy of morality in his book The Science of Good and Evil. He says we become progressively more moral as we expand our sphere of caring from self to immediate family to relatives to strangers to groups to nations to animals to the entire biosphere.


We have the capability to understand the psychology of our instinctive morality, overcome our automatic gut reactions when appropriate, and replace them with something better. We can aspire to overcome tribalism and become a global tribe that works towards the greatest possible happiness and welfare for all its members simply because it’s good. We can’t define good in any justifiable abstract philosophical way, but we can enhance the moral instincts evolution equipped us with to create a pragmatic utilitarianism that works for the benefit of everyone.

Greene’s ideas are applicable to controversies in medicine like abortion, euthanasia, circumcision, mandatory vaccination, universal healthcare coverage, and policies about CAM. They also apply to major global problems like poverty, violent conflict, terrorism, and global warming/environmental concerns and to domestic problems like taxes, capital punishment, gay rights, and many others. His book will make you think and will challenge you to recognize that you, too, have tribal biases. It’s well worth reading.



  • Harriet Hall, MD also known as The SkepDoc, is a retired family physician who writes about pseudoscience and questionable medical practices. She received her BA and MD from the University of Washington, did her internship in the Air Force (the second female ever to do so),  and was the first female graduate of the Air Force family practice residency at Eglin Air Force Base. During a long career as an Air Force physician, she held various positions from flight surgeon to DBMS (Director of Base Medical Services) and did everything from delivering babies to taking the controls of a B-52. She retired with the rank of Colonel.  In 2008 she published her memoirs, Women Aren't Supposed to Fly.

Posted by Harriet Hall

Harriet Hall, MD also known as The SkepDoc, is a retired family physician who writes about pseudoscience and questionable medical practices. She received her BA and MD from the University of Washington, did her internship in the Air Force (the second female ever to do so),  and was the first female graduate of the Air Force family practice residency at Eglin Air Force Base. During a long career as an Air Force physician, she held various positions from flight surgeon to DBMS (Director of Base Medical Services) and did everything from delivering babies to taking the controls of a B-52. She retired with the rank of Colonel.  In 2008 she published her memoirs, Women Aren't Supposed to Fly.