Over the past decade, Robert Sapolsky—a Stanford professor of biology, of neurology, and of neurosurgery, as well as a bestselling author of popular science books—has added another line to his CV: witness in murder trials.
The hours waiting outside courtrooms are long, the pay beside the point. But the role allows Sapolsky to act in service of a core belief, one rooted in an epiphany he had as a 13-year-old and reinforced by everything he has learned since: that the defendants in the trials in which he testifies—“a world of people who were lost before pre-K”—can’t be fairly judged by the court’s normal standards of premeditation and intent. A life of trauma, he explains to the jury, has invariably left one part of the brain atrophied and another part enlarged. To ask, for example, why such a person, acting initially in self-defense, would continue hitting their aggressor after knocking him unconscious is to ignore neurological reality. “Saying ‘Why didn’t he pick the right choice?’ is absurd,” he says. “Because there was no choice at that moment.”
Sapolsky, a soft-voiced man with a face framed by long ringlets and a bushy beard, now mostly gray, doesn’t obviously radiate star power. He has the gentle mien of a guy you might expect to see sporting Tevas and a tote bag at the farmers market. But he is an uncommonly magnetic speaker, a master at drawing an audience in with Socratic questions, unexpected connections, and sardonic quips, all dotted with data and cinched with seamless segues. On Stanford’s official YouTube channel, home to some 4,000 videos, low-fi recordings of Sapolsky lectures account for half of the 10 most viewed videos, including one, “Introduction to Human Behavioral Biology,” that has been watched nearly 17 million times since 2011 despite a camera that can’t decide whether to zoom in or out. Only Steve Jobs’s 2005 Commencement address has more views. “I watched this video when I was in high school and it was the reason why I decided to take AP biology,” a recent comment reads. “Today I’m almost done with medical school. Dr. Sapolsky, I owe you more than you know!”
“He annoys the hell out of me because he’s the best lecturer at the university,” says law professor Hank Greely, ’74, director of the Center for Law and the Biosciences and of the Program in Neuroscience and Society, who has known Sapolsky since the mid-aughts. “He makes me and many others jealous.”
Sapolsky’s rhetorical powers, however, reliably meet their limits in court. Jurors nod in understanding as he explains why damaged brains make horrible decisions (a substantial percentage of people incarcerated for violent crime have a history of concussive head trauma to the prefrontal cortex). Then the jurors generally proceed as if he’d never been there. In 11 of the 13 cases in which he has testified, the defendant has been found guilty of all charges, including premeditated murder. Which is all to say Sapolsky is not expecting a chorus of hosannas when people get hold of the broader thesis at the center of his new book, Determined: A Science of Life Without Free Will. Sapolsky isn’t simply advancing familiar liberal tendencies to show leniency to the less fortunate with a dash of neuroscience to push things along. He is advocating for something even he concedes sounds crazy: that none of us should face retribution for our actions—or be unduly celebrated for our heroics—because we are no more responsible for what we do than a defendant with a damaged prefrontal cortex. Yes, Sapolsky would agree, we can do what we want, but we can’t choose what it is we want to do. We are not the ultimate captains of our own ships. We have no free will. “We are nothing more or less than the cumulative biological and environmental luck, over which we had no control, that has brought us to any moment,” he writes. “There’s not a single crack of daylight to shoehorn in free will.”
That may sound like a load of poppycock to those of us out in the real world flexing our freedom on the daily. The sense of our own ability to author our lives can seem too evident to doubt. But questions about the existence of free will can render newcomers to the debate a little like Wile E. Coyote after he runs off a cliff: It’s all good until you look down. The idea of free will has challenged thinkers of all stripes for millennia, including the fourth-century theologian St. Augustine, who worked to reconcile an omniscient God—who surely knows the future—with human freedom. If God knows the future, how can we do anything but manifest that knowledge? With the dawn of the Enlightenment and the rise of Newtonian physics, another dilemma took center stage. In a universe governed by the laws of science, where every action follows from action, where cause begets cause, how can our choices be anything but another domino in an endless line of necessary consequences? If we are just matter, mustn’t we behave as such? Where’s the free will in that?
For Sapolsky, the answer has seemed obvious since he was 13. He’d grown up in an Orthodox Jewish home, complete with two refrigerators and two kitchen sinks to keep kosher. But his own religious beliefs came crashing down after he read biblical commentary on a passage in Leviticus that restricts a disabled man from the priesthood. Sapolsky wore leg braces for part of his childhood, and this stricture sent him searching for explanation from a rabbi, who answered by analogy: Much like you wouldn’t sacrifice a lamb with a blemish on its lip, you wouldn’t present God with a priest likewise blemished. The answer struck Sapolsky as unfathomably unfair, precipitating a crisis in his young mind. “One night at 2 o’clock I suddenly woke up and said, ‘Oh, I get it. There’s no such thing as God,’ and then I paused a few seconds, and I said, ‘and there’s no free will,’ and I paused, and I said, ‘and this is a vast, indifferent, empty universe,’” he says. “And suddenly everything fell into place.”
Born of religious angst, this realization began a lifelong interest. As undergrads at Harvard, he and a friend ran a lecture series in their dorm called “The Ethics of Free Will and Determinism,” where they’d entice academic stars such as Noam Chomsky and B.F. Skinner to speak, then spend hours arguing about what they had heard. Some of the notes he consulted while writing his book date back to this era. “That’s how long all of this stuff has been percolating,” he says.
In Determined, Sapolsky takes readers on a tour of their own biology, arguing that what appears to be a decision in any particular instant is shaped not just by events in the moment but also by what was happening seconds, hours, days, weeks, years, and even millennia before. His examination of free will begins as many do, with the experiments of Benjamin Libet, a neurophysiologist at UCSF. In the early ’80s, Libet measured the brain signals of participants who performed a simple task—pushing a button or flexing a wrist—noting on a timer the moment that they made the decision to do so. Their brain signals showed that the people had committed to the act a small but significant amount of time before they believed they had decided to act.
Those findings prompted headlines announcing the end of free will, but Sapolsky acknowledges that the results don’t say much about deeper, more involved decision-making. Free will survives Libet, he says, as it does any single experiment. But Libet’s work is just a small part of the case Sapolsky builds in his book. Our decisions, big and small, are boxed in by the hormones in our blood and the receptors in our brains at the moment of an action, our emotional state in the hours before, our sleep the night before, the development of our prefrontal cortex in adolescence, our stress and fear levels as children, the fetal environment we developed in, the genes we were born with, and the culture we descend from. Communities that trace back to pastoralists, such as shepherds, vulnerable to having their livelihoods rustled away, often have “cultures of honor,” in which relatively minor violations are more likely to meet violent responses than in communities whose ancestors didn’t face the same dread. “Put all the scientific results together from all the relevant scientific disciplines, and there’s no room for free will,” he writes.
Sapolsky is a curious messenger for the notion that free will is an illusion, if only because his early life reads like a Choose Your Own Adventure book. Born in 1957 and raised in long-ago, pre-hip Brooklyn, he developed an early fascination with primates. By 9 or so, while his classmates were lamenting the hapless Mets, he was wearing his parents down with constant visits to the mountain gorilla exhibit at the American Museum of Natural History in Manhattan. By 12, he was writing fan letters to some of the world’s leading primatologists. By high school, he’d cajoled administrators into letting him to do a self-paced study of Swahili. Nearly as soon as he graduated from Harvard, he was living in the Serengeti alongside a troop of baboons, a species with sufficient free time and social insecurity to spend their days literally making each other sick with misery. Those beginnings launched him as a leading field and lab researcher in the health effects of stress, and later, as a pioneer in gene therapy, which in turn gave grist to a critically acclaimed writing career. His 2017 book, Behave: The Biology of Humans at Our Best and Worst, was dubbed “science book of the year” by a New York Times critic. That’s a lot of carpe diem for someone who doesn’t believe he has any free will.
But Sapolsky isn’t saying we can’t do what we want; he’s saying we can’t choose what it is we want. There was no end of forces pushing him down his outwardly unlikely path to the Serengeti—not least a baked-in propensity to do things to the nth degree. But while he wanted to study Swahili and to live with baboons, he didn’t choose to want those things. His desires arose unbidden from an unknown chain of causes. If it were possible for a do-over of the moments when he decided both—with everything down to the atom in the same place—there could only be one outcome: the same one. We don’t stand outside that chain of causality, nudging which way the dominoes fall. It’s not a new idea. “A man can do what he wills, but he cannot will what he wills” is a notion ascribed to the 19th-century German philosopher Arthur Schopenhauer. “You can’t successfully wish for what you’re going to wish for,” Sapolsky says. “You can’t think of what you’re going to think of next, you can’t will yourself to have more willpower, and you can’t make yourself feel things [that] you don’t feel.”
To be sure, “hard determinists” like Sapolsky are a distinct minority. John Martin Fischer, ’75, MA ’75, a philosophy professor at UC Riverside and leading contributor to the philosophy of free will and moral responsibility, believes Sapolsky doesn’t adequately consider the possibility that determinism is consistent with freedom and responsibility. “Assuming determinism,” he says, Sapolsky “leaps too quickly to the conclusion that we lack free will.” In fact, a 2020 survey of more than 1,700 English-speaking philosophers found that just 11 percent believed in no free will. The majority were, like Fischer, compatibilists, who believe that a causally determined universe can be compatible with free will. It’s an eternal debate that can shift on what you mean by free will, according to Alfred Mele, a professor of philosophy at Florida State University who for four years headed the Big Questions in Free Will project, a $4.4 million initiative funded by the John Templeton Foundation, a philanthropic organization that supports scholarship in the sciences, theology, and philosophy. In one “modest” version, Mele says, free will is “having the ability to make—and act on the basis of—rational, informed decisions when you’re not being subject to undue force.” Under that definition, Mele absolutely believes in free will.
It’s more ambiguous if you think free will requires what Mele calls deep openness—that, all things the same, a decision could have gone another way; we could have turned left instead of right or traveled the road not taken. But even with this more “ambitious” version of free will, the jury is still out, he says. “Scientists most definitely have not proved that free will—even ambitious free will—is an illusion,” Mele wrote in his 2014 book Free: Why Science Hasn’t Disproved Free Will. While he agrees there are tremendous influences on our decisions, “the question really is, do all those influences add up to something that gives us no real choice at all?” he says. “I still haven’t seen an argument, a science-based argument, or any argument, that shows that’s the case—that the influences are so great we have no elbow room at all.”
Sapolsky, on the other hand, sees not the slightest wiggle room for even a modest version of free will. Our decisions are the consequences of a “seamless string of influences” extending back through time. “Why did that moment just occur?” he asks. “Because of what came before it”—a cycle repeating forever into the past. If we “freely” choose to do something but there was never a possibility of choosing something else, we’re not free. And if we’re not free, Sapolsky says, there is no more reason to castigate a killer than to punish a broken machine. Killers should receive medical and psychological treatment to address the larger issues that caused the problem; if someone presents a danger, they should be kept safely away from others, he says, offering the model of a medical quarantine or a product recall, where the focus is on avoiding future harm. “Keep dangerous people from damaging others,” he writes, “but do so as straightforwardly and nonjudgmentally as keeping a car with faulty brakes off the road.” If you accept that behavior is the inevitable result of biology and environment, rather than of something as mysterious as morality, you can focus on the serious work to change those concrete causes without the distraction of retribution.
It’s a perspective that attracts plenty of skepticism. Stephen Morse, a professor of law and of psychology and law in psychiatry at the University of Pennsylvania, has, over the years, criticized those making similar arguments as having “brain overclaim syndrome,” whereby scientists and those in their sway make connections too confidently between neurology and questions of the law. “Brains do not commit crimes; people commit crimes,” he writes. And as a practical matter, Sapolsky’s ideas are unlikely to be implemented. Even someone like Greely—who regards Sapolsky’s opinions as occupying “a thoroughly respectable position in the debate”—doubts the fullness of his vision could ever go anywhere. “He’s rowing up Niagara Falls,” he says. “Retributivism is, I think, deeply ingrained in American culture.”
Sapolsky knows he’s asking for the incredible. It’s a mindset even he fails to fulfill far more often than he achieves. But he thinks it’s the only intellectually honest response. He was once asked to work on the case of a white supremacist who, a month after attempting to burn down a mosque, invaded a synagogue and shot four people, killing one. Sapolsky had family members who died in Nazi camps during World War II; as a kid, he held a measuring tape for hours as his architect father worked to rebuild their synagogue, heavily damaged by arson; when his wife put on a production of Cabaret, he struggled to hand out costumes emblazoned with swastikas; from childhood, he has fantasized about capturing Hitler before the dictator could “escape” by suicide. The request to help an antisemitic killer, in other words, chilled him to the core. “Like thousands of ancestors were turning over in their graves,”he says, “and thousands of moral reflexes were running over in my stomach. But, you know, if you really believe this, you gotta do that.” To his great relief, the defendant plea-bargained before trial. “I’m a flaming hypocrite,” Sapolsky says. “No one says this is going to be easy.”
But we have moved beyond blame before, Sapolsky writes in Determined. Centuries ago, epileptic seizures could get you burned as a witch. With the Enlightenment, the punishment became less severe, but the perception of fault persisted. Seizures were viewed as the result of masturbation, unseemly sex, or reading too many books and not spending sufficient time in nature. But in 1808, a person who fatally injured another while having a seizure was, for the first time, acquitted. Society had developed the sense that it wasn’t him—it was his illness. Far more recently, psychiatrists have changed thinking about disorders such as schizophrenia, which, as recently as the 1960s, was blamed on “schizophrenogenic” mothering. Today, in an era in which science has charted the genetic aspects of the disorder, that kind of thinking would make you a laughingstock. One day, our successors may think the same of how we’ve treated killers and kidnappers.
There is another question, never mind the people we refer to as criminals. How would the rest of us fare in a world with no presumption of free will, where praise and punishment wither away? Perhaps not so well. A frequently cited 2008 paper by psychologists Kathleen Vohs and Jonathan Schooler found that participants who read deterministic texts before participating in a game were more likely to cheat. A study by another research team, at Florida State University, gave participants the opportunity to “punish” someone who had rebuffed them earlier by giving them spicy salsa on a tortilla chip that they had to eat. Those who’d read arguments against free will slapped on nearly double the amount of salsa as those who had read something endorsing free will. And this with someone with a low tolerance for spicy food, or so the participants had been told. True or not, free will might be an illusion worth having. “What will our society do if it finds itself without the concept of free will?” Vohs and another researcher later wrote. “It may well reinvent it.”
Sapolsky, though, sees another side to moving past free will: that people who are born into and spend their lives in poverty, or who were otherwise dealt a difficult hand in life, will be relieved of the stigma of their position. He doesn’t expect Determined to sweep aside belief in free will. The pull toward attribution and judgment is too great for any one book to undo. He’ll be satisfied with challenging readers to seriously reconsider their sense that they deserve their good fortune any more than others deserve their bad luck. It’s a fight he’ll continue, though likely no longer in the courtroom. The last time he was due to testify, the prosecutor objected on grounds that Sapolsky didn’t believe in free will. The judge dismissed him. “My sneaking suspicion,” Sapolsky says, “is I have done my last trial.”
Sam Scott is a senior writer at Stanford. Email him at sscott3@stanford.edu.
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