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Turtles All the Way Down

When I was in college, my friends and I had an anecdote that we retold frequently; it went like this (and our retelling was so ritualistic that I suspect this is close to verbatim, forty-five years later):

So, it seems that William James was giving a lecture about the nature of life and the universe. Afterward, an old woman came up and said, "Professor James, you have it all wrong."

To which James asked, "How so, madam?"

"Things aren't at all like you said," she replied. "The world is on the back of a gigantic turtle."

"Hmm." said James, bemused. "That may be so, but where does that turtle stand?"

"On the back of another turtle," she answered.

"But madam," said James indulgently, "where does that turtle stand?"

To which the old woman responded triumphantly: "It's no use, Professor James. It's turtles all the way down!"

Oh, how we loved that story, always told it with the same intonation. We thought it made us seem droll and pithy and attractive.

We used the anecdote as mockery, a pejorative critique of someone clinging unshakably to illogic. We'd be in the dinner hall, and someone had said something nonsensical, where their response to being challenged had made things worse. Inevitably, one of us would smugly say, "It's no use, Professor James!" to which the person, who had heard our stupid anecdote repeatedly, would inevitably respond, "Screw you, just listen. This actually makes sense."

Here is the point of this book: While it may seem ridiculous and nonsensical to explain something by resorting to an infinity of turtles all the way down, it actually is much more ridiculous and nonsensical to believe that somewhere down there, there's a turtle floating in the air. The science of human behavior shows that turtles can't float; instead, it is indeed turtles all the way down.

Someone behaves in a particular way. Maybe it's wonderful and inspiring, maybe it's appalling, maybe it's in the eye of the beholder, or maybe just trivial. And we frequently ask the same basic question: Why did that behavior occur?

If you believe that turtles can float in the air, the answer is that it just happened, that there was no cause besides that person having simply decided to create that behavior. Science has recently provided a much more accurate answer, and when I say "recently," I mean in the last few centuries. The answer is that the behavior happened because something that preceded it caused it to happen. And why did that prior circumstance occur? Because something that preceded it caused it to happen. It's antecedent causes all the way down, not a floating turtle or causeless cause to be found. Or as Maria sings in The Sound of Music, "Nothing comes from nothing, nothing ever could."

To reiterate, when you behave in a particular way, which is to say when your brain has generated a particular behavior, it is because of the determinism that came just before, which was caused by the determinism just before that, and before that, all the way down. The approach of this book is to show how that determinism works, to explore how the biology over which you had no control, interacting with environment over which you had no control, made you you. And when people claim that there are causeless causes of your behavior that they call "free will," they have (a) failed to recognize or not learned about the determinism lurking beneath the surface and/or (b) erroneously concluded that the rarefied aspects of the universe that do work indeterministically can explain your character, morals, and behavior.

Once you work with the notion that every aspect of behavior has deterministic, prior causes, you observe a behavior and can answer why it occurred: as just noted, because of the action of neurons in this or that part of your brain in the preceding second. And in the seconds to minutes before, those neurons were activated by a thought, a memory, an emotion, or sensory stimuli. And in the hours to days before that behavior occurred, the hormones in your circulation shaped those thoughts, memories, and emotions and altered how sensitive your brain was to particular environmental stimuli. And in the preceding months to years, experience and environment changed how those neurons function, causing some to sprout new connections and become more excitable, and causing the opposite in others.

And from there, we hurtle back decades in identifying antecedent causes. Explaining why that behavior occurred requires recognizing how during your adolescence a key brain region was still being constructed, shaped by socialization and acculturation. Further back, there's childhood experience shaping the construction of your brain, with the same then applying to your fetal environment. Moving further back, we have to factor in the genes you inherited and their effects on behavior.

But we're not done yet. That's because everything in your childhood, starting with how you were mothered within minutes of birth, was influenced by culture, which means as well by the centuries of ecological factors that influenced what kind of culture your ancestors invented, and by the evolutionary pressures that molded the species you belong to. Why did that behavior occur? Because of biological and environmental interactions, all the way down.

As a central point of this book, those are all variables that you had little or no control over. You cannot decide all the sensory stimuli in your environment, your hormone levels this morning, whether something traumatic happened to you in the past, the socioeconomic status of your parents, your fetal environment, your genes, whether your ancestors were farmers or herders. Let me state this most broadly, probably at this point too broadly for most readers: 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. You're going to be able to recite this sentence in your irritated sleep by the time we're done.

There are all sorts of aspects about behavior that, while true, are not relevant to where we're heading. For example, the fact that some criminal behavior can be due to psychiatric or neurological problems. That some kids have "learning differences" because of the way their brains work. That some people have trouble with self-restraint, because they grew up without any decent role models or because they're still a teenager with a teenager's brain. That someone has said something hurtful merely because they're tired and stressed, or even because of a medication they're taking.

All of these are circumstances where we recognize that sometimes, biology can impinge on our behavior. This is essentially a nice humane agenda that endorses society's general views about agency and personal responsibility but reminds you to make exceptions for edge cases: judges should consider mitigating factors in criminals' upbringing during sentencing; juvenile murderers shouldn't be executed; the teacher handing out gold stars to the kids who are soaring in learning to read should do something special too for that kid with dyslexia; college admissions officers should consider more than just SAT cutoffs for applicants who have overcome unique challenges.

These are good, sensible ideas that should be instituted if you decide that some people have much less self-control and capacity to freely choose their actions than average, and that at times, we all have much less than we imagine.

We can all agree on that; however, we're heading into very different terrain, one that I suspect most readers will not agree with, which is deciding that we have no free will at all. Here would be some of the logical implications of that being the case: That there can be no such thing as blame, and that punishment as retribution is indefensible-sure, keep dangerous people from damaging others, but do so as straightforwardly and nonjudgmentally as keeping a car with faulty brakes off the road. That it can be okay to praise someone or express gratitude toward them as an instrumental intervention, to make it likely that they will repeat that behavior in the future, or as an inspiration to others, but never because they deserve it. And that this applies to you when you've been smart or self-disciplined or kind. Oh, as long as we're at it, that you recognize that the experience of love is made of the same building blocks that constitute wildebeests or asteroids. That no one has earned or is entitled to being treated better or worse than anyone else. And that it makes as little sense to hate someone as to hate a tornado because it supposedly decided to level your house, or to love a lilac because it supposedly decided to make a wonderful fragrance.

That's what it means to conclude that there is no free will. This is what I've concluded, for a long, long time. And even I think that taking that seriously sounds absolutely nutty.

Moreover, most people agree that it sounds that way. People's beliefs and values, their behavior, their answers to survey questions, their actions as study subjects in the nascent field of "experimental philosophy," show that people believe in free will when it matters-philosophers (about 90 percent), lawyers, judges, jurors, educators, parents, and candlestick makers. As well as scientists, even biologists, even many neurobiologists, when push comes to shove. Work by psychologists Alison Gopnik at UC Berkeley and Tamar Kushnir at Cornell shows that preschool kids already have a robust belief in a recognizable version of free will. And such a belief is widespread (but not universal) among a wide variety of cultures. We are not machines in most people's view; as a clear demonstration, when a...