# Robert Sapolsky Is Simply Not Talking About Compatibilism

Imagine someone wrote a 500-page book called *Taking Down Vegetarianism* and every chapter was about how animals can feel pain. The arguments are well-researched, the science is fascinating, and by the end you're completely convinced that animals suffer. You look up from the book and say: “Yes, that's why I'm a vegetarian… wait, why was it called *Taking Down Vegetarianism?”* That was roughly my experience reading *Robert Sapolsky's* [*Determined: A Science of Life without Free Will*](https://www.amazon.com/Determined-Science-Life-without-Free/dp/0525560971).

The book is a much-lauded [New York Times bestseller](https://www.nytimes.com/books/best-sellers/2023/11/05/hardcover-nonfiction/) for good reason. Sapolsky, a professor of neuroscience at Stanford, is an engaging and articulate writer, and he does a lot to make recent advances in neuroscience accessible.

The trouble comes when he attempts to add philosophy on top of it. He wants to demolish free will, and specifically to "take on" compatibilism, the position I defended in [my previous post](https://thegreymatter.substack.com/p/contra-sam-harris-on-free-will). Unfortunately, he doesn’t. He barely engages with it. Instead, he attacks an incoherent notion so bizarre it wouldn't be free will even if it existed.

![](https://res.cloudinary.com/lesswrong-2-0/image/upload/f_auto,q_auto/v1/mirroredImages/KttJGKQMScHDbJbFt/30076fc22314de222b61f549f4f07a94694544bb9e02fda59b3d473a1e79b2c0/ylxzfw6hrdlfkeqalzjj)

The Problem
-----------

Sapolsky commits his original sin, appropriately enough, at the origin. He tells us that he has written a book about free will, and explains the landscape of beliefs as follows (his italics, my bolding):

> I’m going to be discussing some of the common attitudes held by people writing about free will. These come in four basic flavors:  
> *The world is deterministic and there’s no free will.* In this view, if the former is the case, the latter has to be as well; determinism and free will are not compatible. I am coming from this perspective of “hard incompatibilism.”  
> *The world is deterministic and there is free will.* These folks are emphatic that the world is made of stuff like atoms \[...\] this deterministic world is viewed as compatible with free will. This is roughly 90 percent of philosophers and legal scholars, and **the book will most often be taking on these “compatibilists.”**  
> *The world is not deterministic; there’s no free will.* This is an oddball view that everything important in the world runs on randomness, a supposed basis of free will. \[...\]  
> *The world is not deterministic; there is free will.* These are folks who believe, like I do, that a deterministic world is not compatible with free will—however, no problem, the world isn’t deterministic in their view, opening a door for free-will belief. These “libertarian incompatibilists” are a rarity, and I’ll only occasionally touch on their views.

Then he says this (his italics, my bolding):

> *What Do I Mean by* Free Will?  
> People define *free will* differently. Many focus on agency, whether a person can control their actions, act with intent. Other definitions concern whether, when a behavior occurs, the person knows that there are alternatives available. Others are less concerned with what you do than with vetoing what you don’t want to do. Here’s my take.  
> Suppose that a man pulls the trigger of a gun. Mechanistically, the muscles in his index finger contracted because they were stimulated by a neuron having an action potential (i.e., being in a particularly excited state). That neuron in turn had its action potential because it was stimulated by the neuron just upstream. Which had its own action potential because of the next neuron upstream. And so on.  
> Here’s the challenge to a free willer: **Find me the neuron that started this process in this man’s brain, the neuron that had an action potential for no reason, where no neuron spoke to it just before. Then show me that this neuron’s actions were not influenced by whether the man was tired, hungry, stressed, or in pain at the time. That nothing about this neuron’s function was altered by the sights, sounds, smells, and so on, experienced by the man in the previous minutes, nor by the levels of any hormones marinating his brain in the previous hours to days, nor whether he had experienced a life-changing event in recent months or years. And show me that this neuron’s supposedly freely willed functioning wasn’t affected by the man’s genes, or by the lifelong changes in regulation of those genes caused by experiences during his childhood. Nor by levels of hormones he was exposed to as a fetus, when that brain was being constructed. Nor by the centuries of history and ecology that shaped the invention of the culture in which he was raised. Show me a neuron being a causeless cause in this total sense.**

Sapolsky is making the causal regress argument: trace any decision back through the neural chain, and you'll find prior causes all the way down—neurons, hormones, genes, childhood, culture, and so on. His challenge is to find a break in this chain, a "causeless cause."

But compatibilists don't claim there's a break in the chain. Compatibilists fully accept that decisions are caused by neural processes shaped by biology, environment, and history. That's the whole point of *compatibilism*—free will is *compatible* with this.

So what do compatibilists actually mean by free will? In [my post laying out the case for free will](https://thegreymatter.substack.com/p/contra-sam-harris-on-free-will), I defined free will as the process of running a decision-making algorithm. This process gives us the feeling of free will and is the causal mechanism behind making choices. Unlike Sapolsky's criterion of doing things for "no reason," it *responds* to reasons. Yes, it's influenced by whether you're tired or hungry, but this doesn’t make it unfree. That's it working properly. A decision that could be otherwise if your desires, reasoning, or circumstances were different is exactly the kind of decision compatibilists call free.

But the problem with Sapolsky's definition isn't just that it's *different* from mine; it's that it’s incoherent. It describes something that couldn't exist and wouldn't be free will even if it did. Consider what he's actually asking for: a neuron that fires for no reason, influenced by nothing—not your environment, not your history, not your desires, not your reasoning. What would that even be?

If it's uncorrelated with your past actions, then how is it your free will? Suppose your friends are all playing basketball and you want to play with them. On Sapolsky's account, you *can't*, because then your behavior (playing basketball) would be influenced by your experiences (your friends asking you to play). What kind of “free will” is this? Your "free" actions would have to be disconnected from everything you care about.

It wouldn't let you interact with the world. Imagine a neuron that makes you say your own name, but since it can't respond to your environment, it can't fire *because* someone asked "What's your name?" You'd blurt out your name at random, unable to respond appropriately to anything. This is not free will in any reasonable sense.

Sapolsky frames this as setting a high bar. **But it’s not a high bar. It's an incoherent and nonsensical bar.** If his definitions were satisfied, if we found such causeless neurons, that wouldn’t look the slightest bit like free will. It would be random noise that happens to occur inside your skull. If we found such a neuron, it wouldn't vindicate free will so much as be evidence of a brain malfunction.

This is why I say this isn't just a semantic dispute. If Sapolsky simply defined free will differently from compatibilists, we could argue about whose definition better captures the concept. But you can't have that argument when one side hasn't described a coherent concept at all. Sapolsky could define "your achievement" as an outcome you had no role in causing, but there's no productive debate to be had about whether that definition is too strict or too lenient. It's just not what the word means.

Sloppy Engagement
-----------------

Despite claiming to take on *compatibilism*, he repeatedly tries to disprove it by arguing for *determinism*. Early on, he says:

> This version of compatibilism[^-AEzcZRuetKDKJi49F-1]has produced numerous papers by philosophers and legal scholars concerning the relevance of neuroscience to free will. After reading lots of them, I’ve concluded that they usually boil down to three sentences:
> 
> 1.  Wow, there’ve been all these cool advances in neuroscience, all reinforcing the conclusion that ours is a deterministic world.
> 2.  Some of those neuroscience findings challenge our notions of agency, moral responsibility, and deservedness so deeply that one must conclude that there is no free will.
> 3.  Nah, it still exists.

Perhaps he thinks he’s arguing against compatibilism, but he’s not. Here he is, for example, attributing to compatibilists a view they don't hold:

> For free-will believers, the crux of the issue is lack of predictability—at innumerable junctures in our lives, including highly consequential ones, we choose between X and not-X. And even a vastly knowledgeable observer could not have predicted every such choice.
> 
> \[...\]
> 
> Compatibilists and incompatibilists debate whether free will is possible in a deterministic world, but now you can skip the whole brouhaha because chaoticism supposedly shows that the world isn’t deterministic.

He specifically mentions compatibilists here, but then goes on to say this:

> But now to the critical mistake running through all of this: determinism and predictability are very different things. Even if chaoticism is unpredictable, it is still deterministic.

Sure, chaotic systems are still deterministic, but how is that a refutation of compatibilism? Going back to *his own definition*, compatibilism is the belief that “*The world is deterministic and there is free will*.” How could more evidence of determinism be a refutation of compatibilism?

Also, note that predictability is not a crux. From [my essay](https://thegreymatter.substack.com/p/contra-sam-harris-on-free-will):

> Free will doesn’t require unpredictability. If I offer you a choice between chocolate ice cream and a poke in the eye with a sharp stick, you’ll pick the ice cream every time. That predictability doesn’t mean you lack free will; it just means the algorithm reached an obvious conclusion. The question isn’t about whether the results were predictable, but whether the deliberative control process served as a guide versus being bypassed.

There are other examples of this (see the appendix for one more), but you get the idea.

Dismissiveness
--------------

Instead of engaging with compatibilism, he’s very dismissive of it. Near the end, he says:

> One compatibilist philosopher after another reassuringly proclaims their belief in material, deterministic modernity…yet somehow, there is still room for free will. As might be kinda clear by now, I think that this doesn’t work (see chapters 1, 2, 3, 4, 5, 6…). I suspect that most of them know this as well. When you read between the lines, or sometimes even the lines themselves in their writing, a lot of these compatibilists are actually saying that there has to be free will because it would be a total downer otherwise, doing contortions to make an emotional stance seem like an intellectual one.

This is not even engaging with the arguments. For what it’s worth, I explicitly say I’m not using this as an argument in [my piece](https://thegreymatter.substack.com/p/contra-sam-harris-on-free-will):

> The metaphysical question (does free will exist?) is separate from the sociological question (what happens if people believe it does or doesn’t?). Some argue for free will by saying belief in it leads to good outcomes (personal responsibility, motivation), or that disbelief leads to nihilism or fatalism. Sam \[Harris\] and I agree these arguments are irrelevant to whether free will actually exists. The truth of a claim is independent of the consequences of believing it.

Trying to Answer a Philosophical Question with Science
------------------------------------------------------

This is all very disappointing for a book purportedly about free will. I think where Sapolsky goes wrong is that he's trying to answer a philosophical question with science alone. Science can certainly *inform* the question but it cannot *settle* it.

Look, I like science. Science can tell us a lot about the world. It can tell us the neural mechanisms behind decision-making in the brain, the timing of conscious awareness relative to neural activity (as in the famous Libet experiments), and how factors like brain lesions or physical trauma (e.g. [Phineas Gage](https://en.wikipedia.org/wiki/Phineas_Gage)) affect behavior.

But science can’t tell us everything. Science tells us what the world is like, but it can’t tell us, given that world, which concepts make sense and how to apply them.

Consider a thermostat. Science can tell us every physical fact about it: how there’s a bimetallic strip and a circuit and so on. But it can't tell us whether the thermostat is "making a decision." That's a conceptual question about what it means to "make a decision" and where we draw its boundaries. No additional measurement will resolve it. No scientist will ever find a belief, a self, or an iota of free will under a microscope. That's the domain of philosophy.

The free will debate has exactly this structure. Sapolsky and compatibilists agree on the neuroscience. They disagree about whether what the brain does counts as "free will”. Does "free will" require freedom from the laws of physics? Or does it mean the ability to act according to one's desires and reasons, even if those are physically caused? These are questions about how to understand agency, responsibility, and explanation in light of the science. They’re not questions that brain scans can settle.

Sapolsky writes as if piling up scientific facts settles the question. It doesn't. We still have to think carefully about which concepts have earned their keep and which haven't. We have to think about how we interpret the human experience in light of the data. And he simply refuses to consider such questions.

Conclusion
----------

I worry this review has made the book seem worse than it is. There's genuinely interesting neuroscience in it. If you're skeptical of determinism, this is a good book to read and the science is mostly[^69wmi049bt3]solid and often fascinating.

I should also note that Sapolsky and I are pushing in the same direction on the question of retributive punishment, which is arguably what matters most. He says:

> And we need to accept the absurdity of hating any person for anything they've done; ultimately, that hatred is sadder than hating the sky for storming, hating the earth when it quakes, hating a virus because it's good at getting into lung cells.

I'm with him on this point. You don't need to deny free will to reject retribution, but if that's where his argument leads people, I'll take it.

I do wish he had actually engaged with compatibilism, the position he claimed to take on. The book promised such, yet delivered an attack on an incoherent strawman. Read it for the neuroscience. Just know that the confrontation with compatibilism he promises never quite arrives.

Appendix
========

You’ve got the idea by now. But if you’d like one more example of how he’s not talking about compatibilist free:

> Let’s frame this in the context of human behavior. It’s 1922, and you’re presented with a hundred young adults destined to live conventional lives. You’re told that in about forty years, one of the hundred is going to diverge from that picture, becoming impulsive and socially inappropriate to a criminal extent. Here are blood samples from each of those people, check them out. And there’s no way to predict which person is above chance levels.
> 
> It’s 2022. Same cohort with, again, one person destined to go off the rails forty years hence. Again, here are their blood samples. This time, this century, you use them to sequence everyone’s genome. You discover that one individual has a mutation in a gene called MAPT, which codes for something in the brain called the tau protein. And as a result, you can accurately predict that it will be that person, because by age sixty, he will be showing the symptoms of behavioral variant frontotemporal dementia.
> 
> Back to the 1922 cohort. The person in question has started shoplifting, threatening strangers, urinating in public. Why did he behave that way? Because he chose to do so.
> 
> Year 2022’s cohort, same unacceptable acts. Why will he have behaved that way? Because of a deterministic mutation in one gene.
> 
> According to the logic of the thinkers just quoted \[He had quoted many different scientists and philosophers, whose views I do not know\], the 1922 person’s behavior resulted from free will. Not “resulted from behavior we would erroneously attribute to free will.” It was free will. And in 2022, it is not free will. In this view, “free will” is what we call the biology that we don’t understand on a predictive level yet, and when we do understand it, it stops being free will. Not that it stops being mistaken for free will. It literally stops being. There is something wrong if an instance of free will exists only until there is a decrease in our ignorance. As the crucial point, our intuitions about free will certainly work that way, but free will itself can’t.

I can’t speak to what other people believe, but he’s simply not talking about compatibilists here. He might think he is, but he’s not.

[^-AEzcZRuetKDKJi49F-1]:  

[^69wmi049bt3]: There is a noticeable step-down in quality when he gets to science outside his field though. For example, he approvingly cites the famous Israeli “hungry judges” study:It’s the same with hunger. Here’s one study that should stop you in your tracks (and was first referred to in the last chapter). The researchers studied a group of judges overseeing more than a thousand parole board decisions. What best predicted whether a judge granted someone parole versus more jail time? How long it had been since they had eaten a meal. Appear before the judge soon after she’s had a meal, and there was a roughly 65 percent chance of parole; appear a few hours after a meal, and there was close to a 0 percent chance.A separate study followed up and interviewed people from the Israeli Prison Service and learned that “case ordering is not random”. They found that groups of cases were done in a single session, and “within each session, unrepresented prisoners usually go last and are less likely to be granted parole than prisoners with attorneys.”I can hear the angel with PRCTSD (post-replication crisis traumatic stress disorder) on my shoulder yelling, “Confounders! Have you ensured there are absolutely NO confounders?” The effect size is simply too large for us not to be suspicious. The study sounds shocking, but is completely meaningless if there’s a single confounding factor. The implicit correlation -> causation connection relies on the hidden assumption that the order that cases reach a judge is random. I’ve talked about this paper before (clearly he’s not a blog reader—big mistake imho) where I said: Since then, the study has also failed to replicate in other (better-controlled) contexts. See Hungry Professors? Decision Biases Are Less Widespread than Previously Thought by Bergonzoli et al.