Part 2

The Genealogy of Morals

The five spheres are good candidates for a periodic table of the moral sense not only because they are ubiquitous but also because they appear to have deep evolutionary roots. The impulse to avoid harm, which gives trolley ponderers the willies when they consider throwing a man off a bridge, can also be found in rhesus monkeys, who go hungry rather than pull a chain that delivers food to them and a shock to another monkey. Respect for authority is clearly related to the pecking orders of dominance and appeasement that are widespread in the animal kingdom. The purity-defilement contrast taps the emotion of disgust that is triggered by potential disease vectors like bodily effluvia, decaying flesh and unconventional forms of meat, and by risky sexual practices like incest.

The other two moralized spheres match up with the classic examples of how altruism can evolve that were worked out by sociobiologists in the 1960s and 1970s and made famous by Richard Dawkins in his book ''The Selfish Gene.'' Fairness is very close to what scientists call reciprocal altruism, where a willingness to be nice to others can evolve as long as the favor helps the recipient more than it costs the giver and the recipient returns the favor when fortunes reverse. The analysis makes it sound as if reciprocal altruism comes out of a robotlike calculation, but in fact Robert Trivers, the biologist who devised the theory, argued that it is implemented in the brain as a suite of moral emotions. Sympathy prompts a person to offer the first favor, particularly to someone in need for whom it would go the furthest. Anger protects a person against cheaters who accept a favor without reciprocating, by impelling him to punish the ingrate or sever the relationship. Gratitude impels a beneficiary to reward those who helped him in the past. Guilt prompts a cheater in danger of being found out to repair the relationship by redressing the misdeed and advertising that he will behave better in the future (consistent with Mencken's definition of conscience as ''the inner voice which warns us that someone might be looking''). Many experiments on who helps whom, who likes whom, who punishes whom and who feels guilty about what have confirmed these predictions.

Community, the very different emotion that prompts people to share and sacrifice without an expectation of payback, may be rooted in nepotistic altruism, the empathy and solidarity we feel toward our relatives (and which evolved because any gene that pushed an organism to aid a relative would have helped copies of itself sitting inside that relative). In humans, of course, communal feelings can be lavished on nonrelatives as well. Sometimes it pays people (in an evolutionary sense) to love their companions because their interests are yoked, like spouses with common children, in-laws with common relatives, friends with common tastes or allies with common enemies. And sometimes it doesn't pay them at all, but their kinship-detectors have been tricked into treating their groupmates as if they were relatives by tactics like kinship metaphors (blood brothers, fraternities, the fatherland), origin myths, communal meals and other bonding rituals.

Juggling the Spheres

All this brings us to a theory of how the moral sense can be universal and variable at the same time. The five moral spheres are universal, a legacy of evolution. But how they are ranked in importance, and which is brought in to moralize which area of social life -- sex, government, commerce, religion, diet and so on -- depends on the culture. Many of the flabbergasting practices in faraway places become more intelligible when you recognize that the same moralizing impulse that Western elites channel toward violations of harm and fairness (our moral obsessions) is channeled elsewhere to violations in the other spheres. Think of the Japanese fear of nonconformity (community), the holy ablutions and dietary restrictions of Hindus and Orthodox Jews (purity), the outrage at insulting the Prophet among Muslims (authority). In the West, we believe that in business and government, fairness should trump community and try to root out nepotism and cronyism. In other parts of the world this is incomprehensible -- what heartless creep would favor a perfect stranger over his own brother?

The ranking and placement of moral spheres also divides the cultures of liberals and conservatives in the United States. Many bones of contention, like homosexuality, atheism and one-parent families from the right, or racial imbalances, sweatshops and executive pay from the left, reflect different weightings of the spheres. In a large Web survey, Haidt found that liberals put a lopsided moral weight on harm and fairness while playing down group loyalty, authority and purity. Conservatives instead place a moderately high weight on all five. It's not surprising that each side thinks it is driven by lofty ethical values and that the other side is base and unprincipled.

Reassigning an activity to a different sphere, or taking it out of the moral spheres altogether, isn't easy. People think that a behavior belongs in its sphere as a matter of sacred necessity and that the very act of questioning an assignment is a moral outrage. The psychologist Philip Tetlock has shown that the mentality of taboo -- a conviction that some thoughts are sinful to think -- is not just a superstition of Polynesians but a mind-set that can easily be triggered in college-educated Americans. Just ask them to think about applying the sphere of reciprocity to relationships customarily governed by community or authority. When Tetlock asked subjects for their opinions on whether adoption agencies should place children with the couples willing to pay the most, whether people should have the right to sell their organs and whether they should be able to buy their way out of jury duty, the subjects not only disagreed but felt personally insulted and were outraged that anyone would raise the question.

The institutions of modernity often question and experiment with the way activities are assigned to moral spheres. Market economies tend to put everything up for sale. Science amoralizes the world by seeking to understand phenomena rather than pass judgment on them. Secular philosophy is in the business of scrutinizing all beliefs, including those entrenched by authority and tradition. It's not surprising that these institutions are often seen to be morally corrosive.

Is Nothing Sacred?

And ''morally corrosive'' is exactly the term that some critics would apply to the new science of the moral sense. The attempt to dissect our moral intuitions can look like an attempt to debunk them. Evolutionary psychologists seem to want to unmask our noblest motives as ultimately self-interested -- to show that our love for children, compassion for the unfortunate and sense of justice are just tactics in a Darwinian struggle to perpetuate our genes. The explanation of how different cultures appeal to different spheres could lead to a spineless relativism, in which we would never have grounds to criticize the practice of another culture, no matter how barbaric, because ''we have our kind of morality and they have theirs.'' And the whole enterprise seems to be dragging us to an amoral nihilism, in which morality itself would be demoted from a transcendent principle to a figment of our neural circuitry.

In reality, none of these fears are warranted, and it's important to see why not. The first misunderstanding involves the logic of evolutionary explanations. Evolutionary biologists sometimes anthropomorphize DNA for the same reason that science teachers find it useful to have their students imagine the world from the viewpoint of a molecule or a beam of light. One shortcut to understanding the theory of selection without working through the math is to imagine that the genes are little agents that try to make copies of themselves.

Unfortunately, the meme of the selfish gene escaped from popular biology books and mutated into the idea that organisms (including people) are ruthlessly self-serving. And this doesn't follow. Genes are not a reservoir of our dark unconscious wishes. ''Selfish'' genes are perfectly compatible with selfless organisms, because a gene's metaphorical goal of selfishly replicating itself can be implemented by wiring up the brain of the organism to do unselfish things, like being nice to relatives or doing good deeds for needy strangers. When a mother stays up all night comforting a sick child, the genes that endowed her with that tenderness were ''selfish'' in a metaphorical sense, but by no stretch of the imagination is she being selfish.

Nor does reciprocal altruism -- the evolutionary rationale behind fairness -- imply that people do good deeds in the cynical expectation of repayment down the line. We all know of unrequited good deeds, like tipping a waitress in a city you will never visit again and falling on a grenade to save platoonmates. These bursts of goodness are not as anomalous to a biologist as they might appear.

In his classic 1971 article, Trivers, the biologist, showed how natural selection could push in the direction of true selflessness. The emergence of tit-for-tat reciprocity, which lets organisms trade favors without being cheated, is just a first step. A favor-giver not only has to avoid blatant cheaters (those who would accept a favor but not return it) but also prefer generous reciprocators (those who return the biggest favor they can afford) over stingy ones (those who return the smallest favor they can get away with). Since it's good to be chosen as a recipient of favors, a competition arises to be the most generous partner around. More accurately, a competition arises to appear to be the most generous partner around, since the favor-giver can't literally read minds or see into the future. A reputation for fairness and generosity becomes an asset.

Now this just sets up a competition for potential beneficiaries to inflate their reputations without making the sacrifices to back them up. But it also pressures the favor-giver to develop ever-more-sensitive radar to distinguish the genuinely generous partners from the hypocrites. This arms race will eventually reach a logical conclusion. The most effective way to seem generous and fair, under harsh scrutiny, is to be generous and fair. In the long run, then, reputation can be secured only by commitment. At least some agents evolve to be genuinely high-minded and self-sacrificing -- they are moral not because of what it brings them but because that's the kind of people they are.

Of course, a theory that predicted that everyone always sacrificed themselves for another's good would be as preposterous as a theory that predicted that no one ever did. Alongside the niches for saints there are niches for more grudging reciprocators, who attract fewer and poorer partners but don't make the sacrifices necessary for a sterling reputation. And both may coexist with outright cheaters, who exploit the unwary in one-shot encounters. An ecosystem of niches, each with a distinct strategy, can evolve when the payoff of each strategy depends on how many players are playing the other strategies. The human social environment does have its share of generous, grudging and crooked characters, and the genetic variation in personality seems to bear the fingerprints of this evolutionary process.

Is Morality a Figment?

So a biological understanding of the moral sense does not entail that people are calculating maximizers of their genes or self-interest. But where does it leave the concept of morality itself?

Here is the worry. The scientific outlook has taught us that some parts of our subjective experience are products of our biological makeup and have no objective counterpart in the world. The qualitative difference between red and green, the tastiness of fruit and foulness of carrion, the scariness of heights and prettiness of flowers are design features of our common nervous system, and if our species had evolved in a different ecosystem or if we were missing a few genes, our reactions could go the other way. Now, if the distinction between right and wrong is also a product of brain wiring, why should we believe it is any more real than the distinction between red and green? And if it is just a collective hallucination, how could we argue that evils like genocide and slavery are wrong for everyone, rather than just distasteful to us?

Putting God in charge of morality is one way to solve the problem, of course, but Plato made short work of it 2,400 years ago. Does God have a good reason for designating certain acts as moral and others as immoral? If not -- if his dictates are divine whims -- why should we take them seriously? Suppose that God commanded us to torture a child. Would that make it all right, or would some other standard give us reasons to resist? And if, on the other hand, God was forced by moral reasons to issue some dictates and not others -- if a command to torture a child was never an option -- then why not appeal to those reasons directly?

This throws us back to wondering where those reasons could come from, if they are more than just figments of our brains. They certainly aren't in the physical world like wavelength or mass. The only other option is that moral truths exist in some abstract Platonic realm, there for us to discover, perhaps in the same way that mathematical truths (according to most mathematicians) are there for us to discover. On this analogy, we are born with a rudimentary concept of number, but as soon as we build on it with formal mathematical reasoning, the nature of mathematical reality forces us to discover some truths and not others. (No one who understands the concept of two, the concept of four and the concept of addition can come to any conclusion but that 2 + 2 = 4.) Perhaps we are born with a rudimentary moral sense, and as soon as we build on it with moral reasoning, the nature of moral reality forces us to some conclusions but not others.

Moral realism, as this idea is called, is too rich for many philosophers' blood. Yet a diluted version of the idea -- if not a list of cosmically inscribed Thou-Shalts, then at least a few If-Thens -- is not crazy. Two features of reality point any rational, self-preserving social agent in a moral direction. And they could provide a benchmark for determining when the judgments of our moral sense are aligned with morality itself.

One is the prevalence of nonzero-sum games. In many arenas of life, two parties are objectively better off if they both act in a nonselfish way than if each of them acts selfishly. You and I are both better off if we share our surpluses, rescue each other's children in danger and refrain from shooting at each other, compared with hoarding our surpluses while they rot, letting the other's child drown while we file our nails or feuding like the Hatfields and McCoys. Granted, I might be a bit better off if I acted selfishly at your expense and you played the sucker, but the same is true for you with me, so if each of us tried for these advantages, we'd both end up worse off. Any neutral observer, and you and I if we could talk it over rationally, would have to conclude that the state we should aim foris the one in which we both are unselfish. These spreadsheet projections are not quirks of brain wiring, nor are they dictated by a supernatural power; they are in the nature of things.

The other external support for morality is a feature of rationality itself: that it cannot depend on the egocentric vantage point of the reasoner. If I appeal to you to do anything that affects me -- to get off my foot, or tell me the time or not run me over with your car -- then I can't do it in a way that privileges my interests over yours (say, retaining my right to run you over with my car) if I want you to take me seriously. Unless I am Galactic Overlord, I have to state my case in a way that would force me to treat you in kind. I can't act as if my interests are special just because I'm me and you're not, any more than I can persuade you that the spot I am standing on is a special place in the universe just because I happen to be standing on it.

Not coincidentally, the core of this idea -- the interchangeability of perspectives -- keeps reappearing in history's best-thought-through moral philosophies, including the Golden Rule (itself discovered many times); Spinoza's Viewpoint of Eternity; the Social Contract of Hobbes, Rousseau and Locke; Kant's Categorical Imperative; and Rawls's Veil of Ignorance. It also underlies Peter Singer's theory of the Expanding Circle -- the optimistic proposal that our moral sense, though shaped by evolution to overvalue self, kin and clan, can propel us on a path of moral progress, as our reasoning forces us to generalize it to larger and larger circles of sentient beings.

Doing Better by Knowing Ourselves

Morality, then, is still something larger than our inherited moral sense, and the new science of the moral sense does not make moral reasoning and conviction obsolete. At the same time, its implications for our moral universe are profound.

At the very least, the science tells us that even when our adversaries' agenda is most baffling, they may not be amoral psychopaths but in the throes of a moral mind-set that appears to them to be every bit as mandatory and universal as ours does to us. Of course, some adversaries really are psychopaths, and others are so poisoned by a punitive moralization that they are beyond the pale of reason. (The actor Will Smith had many historians on his side when he recently speculated to the press that Hitler thought he was acting morally.) But in any conflict in which a meeting of the minds is not completely hopeless, a recognition that the other guy is acting from moral rather than venal reasons can be a first patch of common ground. One side can acknowledge the other's concern for community or stability or fairness or dignity, even while arguing that some other value should trump it in that instance. With affirmative action, for example, the opponents can be seen as arguing from a sense of fairness, not racism, and the defenders can be seen as acting from a concern with community, not bureaucratic power. Liberals can ratify conservatives' concern with families while noting that gay marriage is perfectly consistent with that concern.

The science of the moral sense also alerts us to ways in which our psychological makeup can get in the way of our arriving at the most defensible moral conclusions. The moral sense, we are learning, is as vulnerable to illusions as the other senses. It is apt to confuse morality per se with purity, status and conformity. It tends to reframe practical problems as moral crusades and thus see their solution in punitive aggression. It imposes taboos that make certain ideas indiscussible. And it has the nasty habit of always putting the self on the side of the angels.

Though wise people have long reflected on how we can be blinded by our own sanctimony, our public discourse still fails to discount it appropriately. In the worst cases, the thoughtlessness of our brute intuitions can be celebrated as a virtue. In his influential essay ''The Wisdom of Repugnance,'' Leon Kass, former chair of the President's Council on Bioethics, argued that we should disregard reason when it comes to cloning and other biomedical technologies and go with our gut: ''We are repelled by the prospect of cloning human beings . . . because we intuit and feel, immediately and without argument, the violation of things that we rightfully hold dear. . . . In this age in which everything is held to be permissible so long as it is freely done . . . repugnance may be the only voice left that speaks up to defend the central core of our humanity. Shallow are the souls that have forgotten how to shudder.''

There are, of course, good reasons to regulate human cloning, but the shudder test is not one of them. People have shuddered at all kinds of morally irrelevant violations of purity in their culture: touching an untouchable, drinking from the same water fountain as a Negro, allowing Jewish blood to mix with Aryan blood, tolerating sodomy between consenting men. And if our ancestors' repugnance had carried the day, we never would have had autopsies, vaccinations, blood transfusions, artificial insemination, organ transplants and in vitro fertilization, all of which were denounced as immoral when they were new.

There are many other issues for which we are too quick to hit the moralization button and look for villains rather than bug fixes. What should we do when a hospital patient is killed by a nurse who administers the wrong drug in a patient's intravenous line? Should we make it easier to sue the hospital for damages? Or should we redesign the IV fittings so that it's physically impossible to connect the wrong bottle to the line?

And nowhere is moralization more of a hazard than in our greatest global challenge. The threat of human-induced climate change has become the occasion for a moralistic revival meeting. In many discussions, the cause of climate change is overindulgence (too many S.U.V.'s) and defilement (sullying the atmosphere), and the solution is temperance (conservation) and expiation (buying carbon offset coupons). Yet the experts agree that these numbers don't add up: even if every last American became conscientious about his or her carbon emissions, the effects on climate change would be trifling, if for no other reason than that two billion Indians and Chinese are unlikely to copy our born-again abstemiousness. Though voluntary conservation may be one wedge in an effective carbon-reduction pie, the other wedges will have to be morally boring, like a carbon tax and new energy technologies, or even taboo, like nuclear power and deliberate manipulation of the ocean and atmosphere. Our habit of moralizing problems, merging them with intuitions of purity and contamination, and resting content when we feel the right feelings, can get in the way of doing the right thing.

Far from debunking morality, then, the science of the moral sense can advance it, by allowing us to see through the illusions that evolution and culture have saddled us with and to focus on goals we can share and defend. As Anton Chekhov wrote, ''Man will become better when you show him what he is like.''

Steven Pinker is the Johnstone Family Professor of Psychology at Harvard University and the author of ''The Language Instinct'' and ''The Stuff of Thought: Language as a Window Into Human Nature.''