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The Biological Basis of Morality
Do we invent our moral absolutes in order to make society workable? Or are these enduring principles expressed to us by some transcendent or Godlike authority? Efforts to resolve this conundrum have perplexed, sometimes inflamed, our best minds for centuries, but the natural sciences are telling us more and more about the choices we make and our reasons for making them

by Edward O. Wilson

The online version of this article appears in two parts. Click here to go to part two.


Biomorality CENTURIES of debate on the origin of ethics come down to this: Either ethical principles, such as justice and human rights, are independent of human experience, or they are human inventions. The distinction is more than an exercise for academic philosophers. The choice between these two understandings makes all the difference in the way we view ourselves as a species. It measures the authority of religion, and it determines the conduct of moral reasoning.

The two assumptions in competition are like islands in a sea of chaos, as different as life and death, matter and the void. One cannot learn which is correct by pure logic; the answer will eventually be reached through an accumulation of objective evidence. Moral reasoning, I believe, is at every level intrinsically consilient with -- compatible with, intertwined with -- the natural sciences. (I use a form of the word "consilience" -- literally a "jumping together" of knowledge as a result of the linking of facts and fact-based theory across disciplines to create a common groundwork of explanation -- because its rarity has preserved its precision.)
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Go to part two of this article.

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  • "Back From Chaos," by Edward O. Wilson (March, 1998)
    "One of the century's most important scientists argues, against fashion, that ... we will discover underlying all forms of knowledge a fundamental unity."


  • "Can We Be Good Without God?" by Glenn Tinder (December, 1989)
    Many of the virtues of liberal democracy, such as a belief in the dignity and equality of all people, have strong roots in the union of the spiritual and the political achieved in the vision of Christianity. Can such values survive without these particular roots? An essay on the political meaning of Christianity.

  • "Thinking About Crime," by James Q. Wilson (September, 1983)
    "Some combination of constitutional traits and early family experiences accounts for more of the variation among young persons in their serious criminality than any other factors, and serious misconduct that appears relatively early in life tends to persist into adulthood."


  • Every thoughtful person has an opinion on which premise is correct. But the split is not, as popularly supposed, between religious believers and secularists. It is between transcendentalists, who think that moral guidelines exist outside the human mind, and empiricists, who think them contrivances of the mind. In simplest terms, the options are as follows: I believe in the independence of moral values, whether from God or not, and I believe that moral values come from human beings alone, whether or not God exists.

    Theologians and philosophers have almost always focused on transcendentalism as the means to validate ethics. They seek the grail of natural law, which comprises freestanding principles of moral conduct immune to doubt and compromise. Christian theologians, following Saint Thomas Aquinas's reasoning in Summa Theologiae, by and large consider natural law to be an expression of God's will. In this view, human beings have an obligation to discover the law by diligent reasoning and to weave it into the routine of their daily lives. Secular philosophers of a transcendental bent may seem to be radically different from theologians, but they are actually quite similar, at least in moral reasoning. They tend to view natural law as a set of principles so powerful, whatever their origin, as to be self-evident to any rational person. In short, transcendental views are fundamentally the same whether God is invoked or not.

    For example, when Thomas Jefferson, following John Locke, derived the doctrine of natural rights from natural law, he was more concerned with the power of transcendental statements than with their origin, divine or secular. In the Declaration of Independence he blended secular and religious presumptions in one transcendentalist sentence, thus deftly covering all bets: "We hold these Truths to be self-evident, that all Men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty, and the Pursuit of Happiness." That assertion became the cardinal premise of America's civil religion, the righteous sword wielded by Abraham Lincoln and Martin Luther King Jr., and it endures as the central ethic binding together the diverse peoples of the United States.

    So compelling are such fruits of natural-law theory, especially when the Deity is also invoked, that they may seem to place the transcendentalist assumption beyond question. But to its noble successes must be added appalling failures. It has been perverted many times in the past -- used, for example, to argue passionately for colonial conquest, slavery, and genocide. Nor was any great war ever fought without each side thinking its cause transcendentally sacred in some manner or other.

    So perhaps we need to take empiricism more seriously. In the empiricist view, ethics is conduct favored consistently enough throughout a society to be expressed as a code of principles. It reaches its precise form in each culture according to historical circumstance. The codes, whether adjudged good or evil by outsiders, play an important role in determining which cultures flourish and which decline.

    The crux of the empiricist view is its emphasis on objective knowledge. Because the success of an ethical code depends on how wisely it interprets moral sentiments, those who frame one should know how the brain works, and how the mind develops. The success of ethics also depends on how accurately a society can predict the consequences of particular actions as opposed to others, especially in cases of moral ambiguity.

    The empiricist argument holds that if we explore the biological roots of moral behavior, and explain their material origins and biases, we should be able to fashion a wise and enduring ethical consensus. The current expansion of scientific inquiry into the deeper processes of human thought makes this venture feasible.

    The choice between transcendentalism and empiricism will be the coming century's version of the struggle for men's souls. Moral reasoning will either remain centered in idioms of theology and philosophy, where it is now, or shift toward science-based material analysis. Where it settles will depend on which world view is proved correct, or at least which is more widely perceived to be correct.

    Ethicists, scholars who specialize in moral reasoning, tend not to declare themselves on the foundations of ethics, or to admit fallibility. Rarely do we see an argument that opens with the simple statement This is my starting point, and it could be wrong. Ethicists instead favor a fretful passage from the particular to the ambiguous, or the reverse -- vagueness into hard cases. I suspect that almost all are transcendentalists at heart, but they rarely say so in simple declarative sentences. One cannot blame them very much; explaining the ineffable is difficult.

    I am an empiricist. On religion I lean toward deism, but consider its proof largely a problem in astrophysics. The existence of a God who created the universe (as envisioned by deism) is possible, and the question may eventually be settled, perhaps by forms of material evidence not yet imagined. Or the matter may be forever beyond human reach. In contrast, and of far greater importance to humanity, the idea of a biological God, one who directs organic evolution and intervenes in human affairs (as envisioned by theism), is increasingly contravened by biology and the brain sciences.

    The same evidence, I believe, favors a purely material origin of ethics, and it meets the criterion of consilience: causal explanations of brain activity and evolution, while imperfect, already cover most facts known about behavior we term "moral." Although this conception is relativistic (in other words, dependent on personal viewpoint), it can, if evolved carefully, lead more directly and safely to stable moral codes than can transcendentalism, which is also, when one thinks about it, ultimately relativistic.

    Of course, lest I forget, I may be wrong.

    Moral awareness
    Transcendentalism Versus Empiricism

    THE argument of the empiricist has roots that go back to Aristotle's Nicomachean Ethics and, in the beginning of the modern era, to David Hume's A Treatise of Human Nature (1739-1740). The first clear evolutionary elaboration of it was by Charles Darwin, in The Descent of Man (1871).

    Again, religious transcendentalism is bolstered by secular transcendentalism, to which it is fundamentally similar. Immanuel Kant, judged by history the greatest of secular philosophers, addressed moral reasoning very much as a theologian. Human beings, he argued, are independent moral agents with a wholly free will, capable of obeying or breaking moral law: "There is in man a power of self-determination, independent of any coercion through sensuous impulses." Our minds are subject to a categorical imperative, Kant said, of what our actions ought to be. The imperative is a good in itself alone, apart from all other considerations, and it can be recognized by this rule: "Act only on that maxim you wish will become a universal law." Most important, and transcendental, ought has no place in nature. Nature, Kant said, is a system of cause and effect, whereas moral choice is a matter of free will, absent cause and effect. In making moral choices, in rising above mere instinct, human beings transcend the realm of nature and enter a realm of freedom that belongs exclusively to them as rational creatures.

    Now, this formulation has a comforting feel to it, but it makes no sense at all in terms of either material or imaginable entities, which is why Kant, even apart from his tortured prose, is so hard to understand. Sometimes a concept is baffling not because it is profound but because it is wrong. This idea does not accord, we know now, with the evidence of how the brain works.

    In Principia Ethica (1903), G. E. Moore, the founder of modern ethical philosophy, essentially agreed with Kant. In his view, moral reasoning cannot dip into psychology and the social sciences in order to locate ethical principles, because those disciplines yield only a causal picture and fail to illuminate the basis of moral justification. So to reach the normative ought by way of the factual is is to commit a basic error of logic, which Moore called the naturalistic fallacy. John Rawls, in A Theory of Justice (1971), once again traveled the transcendental road. He offered the very plausible suggestion that justice be defined as fairness, which is to be accepted as an intrinsic good. It is the imperative we would follow if we had no starting information about our own future status in life. But in making such a suggestion Rawls ventured no thought on where the human brain comes from or how it works. He offered no evidence that justice-as-fairness is consistent with human nature, hence practicable as a blanket premise. Probably it is, but how can we know except by blind trial and error?

    Had Kant, Moore, and Rawls known modern biology and experimental psychology, they might well not have reasoned as they did. Yet as this century closes, transcendentalism remains firm in the hearts not just of religious believers but also of countless scholars in the social sciences and the humanities who, like Moore and Rawls, have chosen to insulate their thinking from the natural sciences.

    Many philosophers will respond by saying, Ethicists don't need that kind of information. You really can't pass from is to ought. You can't describe a genetic predisposition and suppose that because it is part of human nature, it is somehow transformed into an ethical precept. We must put moral reasoning in a special category, and use transcendental guidelines as required.

    No, we do not have to put moral reasoning in a special category and use transcendental premises, because the posing of the naturalistic fallacy is itself a fallacy. For if ought is not is, what is? To translate is into ought makes sense if we attend to the objective meaning of ethical precepts. They are very unlikely to be ethereal messages awaiting revelation, or independent truths vibrating in a nonmaterial dimension of the mind. They are more likely to be products of the brain and the culture. From the consilient perspective of the natural sciences, they are no more than principles of the social contract hardened into rules and dictates -- the behavioral codes that members of a society fervently wish others to follow and are themselves willing to accept for the common good. Precepts are the extreme on a scale of agreements that range from casual assent, to public sentiment, to law, to that part of the canon considered sacred and unalterable. The scale applied to adultery might read as follows:

    Let's not go further; it doesn't feel right, and it may lead to trouble. (Maybe we ought not.)

    Adultery not only causes feelings of guilt but is generally disapproved of by society. (We probably ought not.)

    Adultery isn't just disapproved of; it's against the law. (We almost certainly ought not.)

    God commands that we avoid this mortal sin. (We absolutely ought not.)

    In transcendental thinking, the chain of causation runs downward from the given ought in religion or natural law through jurisprudence to education and finally to individual choice. The argument from transcendentalism takes the following general form: The order of nature contains supreme principles, either divine or intrinsic, and we will be wise to learn about them and find the means to conform to them. Thus John Rawls opens A Theory of Justice with a proposition he regards as irrevocable: "In a just society the liberties of equal citizenship are taken as settled; the rights secured by justice are not subject to political bargaining or to the calculus of social interests." As many critiques have made clear, that premise can lead to unhappy consequences when applied to the real world, including a tightening of social control and a decline in personal initiative. A very different premise, therefore, is suggested by Robert Nozick in Anarchy, State, and Utopia (1974): "Individuals have rights, and there are things no person or group may do to them (without violating their rights). So strong and far-reaching are these rights that they raise the question of what, if anything, the state and its officials may do." Rawls would point us toward egalitarianism regulated by the state, Nozick toward libertarianism in a minimalist state.

    The empiricist view, in contrast, searching for an origin of ethical reasoning that can be objectively studied, reverses the chain of causation. The individual is seen as predisposed biologically to make certain choices. Through cultural evolution some of the choices are hardened into precepts, then into laws, and, if the predisposition or coercion is strong enough, into a belief in the command of God or the natural order of the universe. The general empiricist principle takes this form: Strong innate feeling and historical experience cause certain actions to be preferred; we have experienced them, and have weighed their consequences, and agree to conform with codes that express them. Let us take an oath upon the codes, invest our personal honor in them, and suffer punishment for their violation. The empiricist view concedes that moral codes are devised to conform to some drives of human nature and to suppress others. Ought is the translation not of human nature but of the public will, which can be made increasingly wise and stable through an understanding of the needs and pitfalls of human nature. The empiricist view recognizes that the strength of commitment can wane as a result of new knowledge and experience, with the result that certain rules may be desacralized, old laws rescinded, and formerly prohibited behavior set free. It also recognizes that for the same reason new moral codes may need to be devised, with the potential of being made sacred in time.

    The Origin of Moral Instincts

    IF the empiricist world view is correct, ought is just shorthand for one kind of factual statement, a word that denotes what society first chose (or was coerced) to do, and then codified. The naturalistic fallacy is thereby reduced to the naturalistic problem. The solution of the problem is not difficult: ought is the product of a material process. The solution points the way to an objective grasp of the origin of ethics.

    A few investigators are now embarked on just such a foundational inquiry. Most agree that ethical codes have arisen by evolution through the interplay of biology and culture. In a sense these investigators are reviving the idea of moral sentiments that was developed in the eighteenth century by the British empiricists Francis Hutcheson, David Hume, and Adam Smith.

    What have been thought of as moral sentiments are now taken to mean moral instincts (as defined by the modern behavioral sciences), subject to judgment according to their consequences. Such sentiments are thus derived from epigenetic rules -- hereditary biases in mental development, usually conditioned by emotion, that influence concepts and decisions made from them. The primary origin of moral instincts is the dynamic relation between cooperation and defection. The essential ingredient for the molding of the instincts during genetic evolution in any species is intelligence high enough to judge and manipulate the tension generated by the dynamism. That level of intelligence allows the building of complex mental scenarios well into the future. It occurs, so far as is known, only in human beings and perhaps their closest relatives among the higher apes.

    A way of envisioning the hypothetical earliest stages of moral evolution is provided by game theory, particularly the solutions to the famous Prisoner's Dilemma. Consider the following typical scenario of the dilemma. Two gang members have been arrested for murder and are being questioned separately. The evidence against them is strong but not irrefutable. The first gang member believes that if he turns state's witness, he will be granted immunity and his partner will be sentenced to life in prison. But he is also aware that his partner has the same option, and that if both of them exercise it, neither will be granted immunity. That is the dilemma. Will the two gang members independently defect, so that both take the hard fall? They will not, because they agreed in advance to remain silent if caught. By doing so, both hope to be convicted on a lesser charge or escape punishment altogether. Criminal gangs have turned this principle of calculation into an ethical precept: Never rat on another member; always be a stand-up guy. Honor does exist among thieves. The gang is a society of sorts; its code is the same as that of a captive soldier in wartime, obliged to give only name, rank, and serial number.

    In one form or another, comparable dilemmas that are solvable by cooperation occur constantly and everywhere in daily life. The payoff is variously money, status, power, sex, access, comfort, or health. Most of these proximate rewards are converted into the universal bottom line of Darwinian genetic fitness: greater longevity and a secure, growing family.

    And so it has most likely always been. Imagine a Paleolithic band of five hunters. One considers breaking away from the others to look for an antelope on his own. If successful, he will gain a large quantity of meat and hide -- five times as much as if he stays with the band and they are successful. But he knows from experience that his chances of success are very low, much less than the chances of the band of five working together. In addition, whether successful alone or not, he will suffer animosity from the others for lessening their prospects. By custom the band members remain together and share equitably the animals they kill. So the hunter stays. He also observes good manners in doing so, especially if he is the one who makes the kill. Boastful pride is condemned, because it rips the delicate web of reciprocity.

    Now suppose that human propensities to cooperate or defect are heritable: some people are innately more cooperative, others less so. In this respect moral aptitude would simply be like almost all other mental traits studied to date. Among traits with documented heritability, those closest to moral aptitude are empathy with the distress of others and certain processes of attachment between infants and their caregivers. To the heritability of moral aptitude add the abundant evidence of history that cooperative individuals generally survive longer and leave more offspring. Following that reasoning, in the course of evolutionary history genes predisposing people toward cooperative behavior would have come to predominate in the human population as a whole.

    Such a process repeated through thousands of generations inevitably gave rise to moral sentiments. With the exception of psychopaths (if any truly exist), every person vividly experiences these instincts variously as conscience, self-respect, remorse, empathy, shame, humility, and moral outrage. They bias cultural evolution toward the conventions that express the universal moral codes of honor, patriotism, altruism, justice, compassion, mercy, and redemption.

    The dark side of the inborn propensity to moral behavior is xenophobia. Because personal familiarity and common interest are vital in social transactions, moral sentiments evolved to be selective. People give trust to strangers with effort, and true compassion is a commodity in chronically short supply. Tribes cooperate only through carefully defined treaties and other conventions. They are quick to imagine themselves the victims of conspiracies by competing groups, and they are prone to dehumanize and murder their rivals during periods of severe conflict. They cement their own group loyalties by means of sacred symbols and ceremonies. Their mythologies are filled with epic victories over menacing enemies.

    The complementary instincts of morality and tribalism are easily manipulated. Civilization has made them more so. Beginning about 10,000 years ago, a tick in geological time, when the agricultural revolution started in the Middle East, in China, and in Mesoamerica, populations increased tenfold in density over those of hunter-gatherer societies. Families settled on small plots of land, villages proliferated, and labor was finely divided as a growing minority of the populace specialized as craftsmen, traders, and soldiers. The rising agricultural societies became increasingly hierarchical. As chiefdoms and then states thrived on agricultural surpluses, hereditary rulers and priestly castes took power. The old ethical codes were transformed into coercive regulations, always to the advantage of the ruling classes. About this time the idea of law-giving gods originated. Their commands lent the ethical codes overpowering authority -- once again, no surprise, in the interests of the rulers.

    Because of the technical difficulty of analyzing such phenomena in an objective manner, and because people resist biological explanations of their higher cortical functions in the first place, very little progress has been made in the biological exploration of the moral sentiments. Even so, it is astonishing that the study of ethics has advanced so little since the nineteenth century. The most distinguishing and vital qualities of the human species remain a blank space on the scientific map. I doubt that discussions of ethics should rest upon the freestanding assumptions of contemporary philosophers who have evidently never given thought to the evolutionary origin and material functioning of the human brain. In no other domain of the humanities is a union with the natural sciences more urgently needed.

    When the ethical dimension of human nature is at last fully opened to such exploration, the innate epigenetic rules of moral reasoning will probably not prove to be aggregated into simple instincts such as bonding, cooperativeness, and altruism. Instead the rules will most probably turn out to be an ensemble of many algorithms, whose interlocking activities guide the mind across a landscape of nuanced moods and choices.

    Such a prestructured mental world may at first seem too complicated to have been created by autonomous genetic evolution alone. But all the evidence of biology suggests that just this process was enough to spawn the millions of species of life surrounding us. Each kind of animal is furthermore guided through its life cycle by unique and often elaborate sets of instinctual algorithms, many of which are beginning to yield to genetic and neurobiological analyses. With all these examples before us, we may reasonably conclude that human behavior originated the same way.


    The online version of this article appears in two parts. Click here to go to part two.

    Edward O. Wilson is the Pellegrino University Research Professor and Honorary Curator in Entomology at Harvard University. His article in this issue is drawn from his book
    Consilience, to be published this month by Knopf.

    Illustrations by Robert Goldstrom

    Copyright © 1998 by The Atlantic Monthly Company. All rights reserved.
    The Atlantic Monthly; April 1998; The Biological Basis of Morality; Volume 281, No. 4; pages 53 - 70.

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