Far from being empty receptacles or universal learners, then, children are equipped with a toolbox of implements for reasoning and learning in particular ways, and those implements must be cleverly recruited to master problems for which they were not designed. That requires not just inserting new facts and skills in children’s minds but debugging and disabling old ones. Students cannot learn Newtonian physics until they unlearn their intuitive impetus-based physics.14 They cannot learn modern biology until they unlearn their intuitive biology, which thinks in terms of vital essences. And they cannot learn evolution until they unlearn their intuitive engineering, which attributes design to the intentions of a designer.15
Schooling also requires pupils to expose and reinforce skills that are ordinarily buried in unconscious black boxes. When children learn to read, the vowels and consonants that are seamlessly woven together in speech must be forced into children’s awareness before they can associate them with squiggles on a page.16 Effective education may also require co-opting old faculties to deal with new demands. Snatches of language can be pressed into service to do calculation, as when we recall the stanza “Five times five is twenty-five.”17 The logic of grammar can be used to grasp large numbers: the expression four thousand three hundred and fifty-seven has the grammatical structure of an English noun phrase like hat, coat, and mittens. When a student parses the number phrase she can call to mind the mental operation of aggregation, which is related to the mathematical operation of addition.18 Spatial cognition is drafted into understanding mathematical relationships through the use of graphs, which turn data or equations into shapes.19 Intuitive engineering supports the learning of anatomy and physiology (organs are understood as gadgets with functions), and intuitive physics supports the learning of chemistry and biology (stuff, including living stuff, is made out of tiny, bouncy, sticky objects).20
Geary points out a final implication. Because much of the content of education is not cognitively natural, the process of mastering it may not always be easy and pleasant, notwithstanding the mantra that learning is fun. Children may be innately motivated to make friends, acquire status, hone motor skills, and explore the physical world, but they are not necessarily motivated to adapt their cognitive faculties to unnatural tasks like formal mathematics. A family, peer group, and culture that ascribe high status to school achievement may be needed to give a child the motive to persevere toward effortful feats of learning whose rewards are apparent only over the long term.21
THE LAYPERSON’S INTUITIVE psychology or “theory of mind” is one of the brain’s most striking abilities. We do not treat other people as wind-up dolls but think of them as being animated by minds: nonphysical entities we cannot see or touch but that are as real to us as bodies and objects. Aside from allowing us to predict people’s behavior from their beliefs and desires, our theory of mind is tied to our ability to empathize and to our conception of life and death. The difference between a dead body and a living one is that a dead body no longer contains the vital force we call a mind. Our theory of mind is the source of the concept of the soul. The ghost in the machine is deeply rooted in our way of thinking about people.
A belief in the soul, in turn, meshes with our moral convictions. The core of morality is the recognition that others have interests as we do—that they “feel want, taste grief, need friends,” as Shakespeare put it—and therefore that they have a right to life, liberty, and the pursuit of their interests. But who are those “others”? We need a boundary that allows us to be callous to rocks and plants but forces us to treat other humans as “persons” that possess inalienable rights. Otherwise, it seems, we would place ourselves on a slippery slope that ends in the disposal of inconvenient people or in grotesque deliberations on the value of individual lives. As Pope John Paul II pointed out, the notion that every human carries infinite value by virtue of possessing a soul would seem to give us that boundary.
Until recently the intuitive concept of the soul served us pretty well. Living people had souls, which come into existence at the moment of conception and leave their bodies when they die. Animals, plants, and inanimate objects do not have souls at all. But science is showing that what we call the soul—the locus of sentience, reason, and will—consists of the information-processing activity of the brain, an organ governed by the laws of biology. In an individual person it comes into existence gradually through the differentiation of tissues growing from a single cell. In the species it came into existence gradually as the forces of evolution modified the brains of simpler animals. And though our concept of souls used to fit pretty well with natural phenomena—a woman was either pregnant or not, a person was either dead or alive—biomedical research is now presenting us with cases where the two are out of register. These cases are not just scientific curiosities but are intertwined with pressing issues such as contraception, abortion, infanticide, animal rights, cloning, euthanasia, and research involving human embryos, especially the harvesting of stem cells.
In the face of these difficult choices it is tempting to look to biology to find or ratify boundaries such as “when life begins.” But that only highlights the clash between two incommensurable ways of conceiving life and mind. The intuitive and morally useful concept of an immaterial spirit simply cannot be reconciled with the scientific concept of brain activity emerging gradually in ontogeny and phylogeny. No matter where we try to draw the line between life and nonlife, or between mind and nonmind, ambiguous cases pop up to challenge our moral intuitions.
The closest event we can find to a thunderclap marking the entry of a soul into the world is the moment of conception. At that instant a new human genome is determined, and we have an entity destined to develop into a unique individual. The Catholic Church and certain other Christian denominations designate conception as the moment of ensoulment and the beginning of life (which, of course, makes abortion a form of murder). But just as a microscope reveals that a straight edge is really ragged, research on human reproduction shows that the “moment of conception” is not a moment at all. Sometimes several sperm penetrate the outer membrane of the egg, and it takes time for the egg to eject the extra chromosomes. What and where is the soul during this interval? Even when a single sperm enters, its genes remain separate from those of the egg for a day or more, and it takes yet another day or so for the newly merged genome to control the cell. So the “moment” of conception is in fact a span of twenty-four to forty-eight hours.22 Nor is the conceptus destined to become a baby. Between two-thirds and three-quarters of them never implant in the uterus and are spontaneously aborted, some because they are genetically defective, others for no discernible reason.
Still, one might say that at whatever point during this interlude the new genome is formed, the specification of a unique new person has come into existence. The soul, by this reasoning, may be identified with the genome. But during the next few days, as the embryo’s cells begin to divide, they can split into several embryos, which develop into identical twins, triplets, and so on. Do identical twins share a soul? Did the Dionne quintuplets make do with one-fifth of a soul each? If not, where did the four extra souls come from? Indeed, every cell in the growing embryo is capable, with the right manipulations, of becoming a new embryo that can grow into a child. Does a multicell embryo consist of one soul per cell, and if so, where do the other souls go when the cells lose that ability? And not only can one embryo become two people, but two embryos can become one person. Occasionally two fertilized eggs, which ordinarily would go on to become fraternal twins, merge into a single embryo that develops into a person who is a genetic chimera: some of her cells have one genome, others have another genome. Does her body house two souls?
For that matter, if human cloning ever became possible (and there appears to be no technical obstacle), every cell in a person’s body would have the special ability that is supposedly unique to a conceptus, namely developing into a human being. True, the genes in a cheek cell can become a person only with unnatural i
ntervention, but that is just as true for an egg that is fertilized in vitro. Yet no one would deny that children conceived by IVF have souls.
The idea that ensoulment takes place at conception is not only hard to reconcile with biology but does not have the moral superiority credited to it. It implies that we should prosecute users of intrauterine contraceptive devices and the “morning-after pill” for murder, because they prevent the conceptus from implanting. It implies that we should divert medical research from curing cancer and heart disease to preventing the spontaneous miscarriages of vast numbers of microscopic conceptuses. It impels us to find surrogate mothers for the large number of embryos left over from IVF that are currently sitting in fertility clinic freezers. It would outlaw research on conception and early embryonic development that promises to reduce infertility, birth defects, and pediatric cancer, and research on stem cells that could lead to treatments for Alzheimer’s disease, Parkinson’s disease, diabetes, and spinal-cord injuries. And it flouts the key moral intuition that other people are worthy of moral consideration because of their feelings—their ability to love, think, plan, enjoy, and suffer—all of which depend on a functioning nervous system.
The enormous moral costs of equating a person with a conceptus, and the cognitive gymnastics required to maintain that belief in the face of modern biology, can sometimes lead to an agonizing reconsideration of deeply held beliefs. In 2001, Senator Orrin Hatch of Utah broke with his longtime allies in the anti-abortion movement and came out in favor of stem-cell research after studying the science of reproduction and meditating on his Mormon faith. “I have searched my conscience,” he said. “I just cannot equate a child living in the womb, with moving toes and fingers and a beating heart, with an embryo in a freezer.”23
The belief that bodies are invested with souls is not just a product of religious doctrine but embedded in people’s psychology and likely to emerge whenever they have not digested the findings of biology. The public reaction to cloning is a case in point. Some people fear that cloning would present us with the option of becoming immortal, others that it could produce an army of obedient zombies, or a source of organs for the original person to harvest when needed. In the recent Arnold Schwarzenegger movie The Sixth Day, clones are called “blanks,” and their DNA gives them only a physical form, not a mind; they acquire a mind when a neural recording of the original person is downloaded into them. When Dolly the sheep was cloned in 1997, the cover of Der Spiegel showed a parade of Claudia Schiffers, Hitlers, and Einsteins, as if being a supermodel, fascist dictator, or scientific genius could be copied along with the DNA.
Clones, in fact, are just identical twins born at different times. If Einstein had a twin, he would not have been a zombie, would not have continued Einstein’s stream of consciousness if Einstein had predeceased him, would not have given up his vital organs without a struggle, and probably would have been no Einstein (since intelligence is only partly heritable). The same would be true of a person cloned from a speck of Einstein. The bizarre misconceptions of cloning can be traced to the persistent belief that the body is suffused with a soul. One conception of cloning, which sets off a fear of an army of zombies, blanks, or organ farms, imagines the process to be the duplication of a body without a soul. The other, which sets off fears of a Faustian grab at immortality or of a resurrected Hitler, conceives of cloning as duplicating the body together with the soul. This conception may also underlie the longing of some bereaved parents for a dead child to be cloned, as if that would bring the child back to life. In fact, the clone would not only grow up in a different world from the one the dead sibling grew up in, but would have different brain tissue and would traverse a different line of sentient experience.
The discovery that what we call “the person” emerges piecemeal from a gradually developing brain forces us to reframe problems in bioethics. It would have been convenient if biologists had discovered a point at which the brain is fully assembled and is plugged in and turned on for the first time, but that is not how brains work. The nervous system emerges in the embryo as a simple tube and differentiates into a brain and spinal cord. The brain begins to function in the fetus, but it continues to wire itself well into childhood and even adolescence. The demand by both religious and secular ethicists that we identify the “criteria for personhood” assumes that a dividing line in brain development can be found. But any claim that such a line has been sighted leads to moral absurdities.
If we set the boundary for personhood at birth, we should be prepared to allow an abortion minutes before birth, despite the lack of any significant difference between a late-term fetus and a neonate. It seems more reasonable to draw the line at viability. But viability is a continuum that depends on the state of current biomedical technology and on the risks of impairment that parents are willing to tolerate in their child. And it invites the obvious rejoinder: if it is all right to abort a twenty-four-week fetus, then why not the barely distinguishable fetus of twenty-four weeks plus one day? And if that is permissible, why not a fetus of twenty-four weeks plus two days, or three days, and so on until birth? On the other hand, if it is impermissible to abort a fetus the day before its birth, then what about two days before, and three days, and so on, all the way back to conception?
We face the same problem in reverse when considering euthanasia and living wills at the end of life. Most people do not depart this world in a puff of smoke but suffer a gradual and uneven breakdown of the various parts of the brain and body. Many kinds and degrees of existence lie between the living and the dead, and that will become even more true as medical technology improves.
We face the problem again in grappling with demands for animal rights. Activists who grant the right to life to any sentient being must conclude that a hamburger eater is a party to murder and that a rodent exterminator is a perpetrator of mass murder. They must outlaw medical research that would sacrifice a few mice but save a million children from painful deaths (since no one would agree to drafting a few human beings for such experiments, and on this view mice have the rights we ordinarily grant to people). On the other hand, an opponent of animal rights who maintains that personhood comes from being a member of Homo sapiens is just a species bigot, no more thoughtful than the race bigots who value the lives of whites more than blacks. After all, other mammals fight to stay alive, appear to experience pleasure, and undergo pain, fear, and stress when their well-being is compromised. The great apes also share our higher pleasures of curiosity and love of kin, and our deeper aches of boredom, loneliness, and grief. Why should those interests be respected for our species but not for others?
Some moral philosophers try to thread a boundary across this treacherous landscape by equating personhood with cognitive traits that humans happen to possess. These include an ability to reflect upon oneself as a continuous locus of consciousness, to form and savor plans for the future, to dread death, and to express a choice not to die.24 At first glance the boundary is appealing because it puts humans on one side and animals and conceptuses on the other. But it also implies that nothing is wrong with killing unwanted newborns, the senile, and the mentally handicapped, who lack the qualifying traits. Almost no one is willing to accept a criterion with those implications.
There is no solution to these dilemmas, because they arise out of a fundamental incommensurability: between our intuitive psychology, with its all-or-none concept of a person or soul, and the brute facts of biology, which tell us that the human brain evolved gradually, develops gradually, and can die gradually. And that means that moral conundrums such as abortion, euthanasia, and animal rights will never be resolved in a decisive and intuitively satisfying way. This does not mean that no policy is defensible and that the whole matter should be left to personal taste, political power, or religious dogma. As the bioethicist Ronald Green has pointed out, it just means we have to reconceptualize the problem: from finding a boundary in nature to choosing a boundary that best trades off the conflicting goods and evils f
or each policy dilemma.25 We should make decisions in each case that can be practically implemented, that maximize happiness, and that minimize current and future suffering. Many of our current policies are already compromises of this sort: research on animals is permitted but regulated; a late-term fetus is not awarded full legal status as a person but may not be aborted unless it is necessary to protect the mother’s life or health. Green notes that the shift from finding boundaries to choosing boundaries is a conceptual revolution of Copernican proportions. But the old conceptualization, which amounts to trying to pinpoint when the ghost enters the machine, is scientifically untenable and has no business guiding policy in the twenty-first century.
The traditional argument against pragmatic, case-by-case decisions is that they lead to slippery slopes. If we allow abortion, we will soon allow infanticide; if we permit research on stem cells, we will bring on a Brave New World of government-engineered humans. But here, I think, the nature of human cognition can get us out of the dilemma rather than pushing us into one. A slippery slope assumes that conceptual categories must have crisp boundaries that allow in-or-out decisions, or else anything goes. But that is not how human concepts work. As we have seen, many everyday concepts have fuzzy boundaries, and the mind distinguishes between a fuzzy boundary and no boundary at all. “Adult” and “child” are fuzzy categories, which is why we could raise the drinking age to twenty-one or lower the voting age to eighteen. But that did not put us on a slippery slope in which we eventually raised the drinking age to fifty or lowered the voting age to five. Those policies really would violate our concepts of “child” and “adult,” fuzzy though their boundaries may be. In the same way, we can bring our concepts of life and mind into register with biological reality without necessarily slipping down a slope.