Can Science Disprove Free Will?

A Review of Robert M. Sapolsky's Book on the Science of Free Will

Photo by Ousa Chea on Unsplash

Anyone who's devoted attention to free will stuff knows that meddlesome, wayward scientists trespassing on philosophical turf is a longstanding bugbear of the armchair-bound set. Shockingly, it's been over a decade since the public fracas between former New Atheist teammates

Sam Harris

and Dan Dennett over free will: Harris (a neuroscience PhD) published a short book on the topic back in 2012; Dennett (an eminent Tufts philosophy prof who recently passed away) reviewed the book with an undeniable soupçon of patronization: “I am not being disingenuous when I say this museum of mistakes is valuable.”¹ Jerry Coyne, a biologist at the University of Chicago, has also attempted to defenestrate free will, and now Robert Sapolsky (Stanford neurobiology professor, MacArthur Genius Grant Recipient, etc.) has made an attempt with his recent book Determinism: the Science of Life Without Free Will.

The scientific threat to free will dates back (at least) to Laplace’s demon. In a classical (i.e., non-quantum-mechanical) world, you can calculate where a particle will be at t₂ with some information about the particle at t₁. So, given determinism, someone with enough data and compute (such as Laplace’s demon) can predict the future—thus, how could anyone have free will?²

The neuroscientific threat to free will is much newer and has focused on Libet studies, wherein scientists measure temporal lacuna between when someone’s brain looks like it made a decision and when that person thinks they made that decision: basically, if scientists looking at your brain can predict your decision-making, then how could you have free will? These studies have invited endless controversy and variation for years, and Sapolsky breezily outlines the various minutiae and snafus like whether the decisions in Libet studies are too inconsequential to resemble decision-making that utilizes free will, etc. He ultimately contends that the Libet controversy is unwarranted, however, because the studies focus on the timing and awareness of peoples’ intentions, and science repeatedly demonstrates that chasing the causality of those intentions further upstream reveals a panoply of inputs that agents mostly don’t even know about (let alone have control over):

“But here’s why these Libetian debates, as well as a criminal justice system that cares only about whether someone’s actions are intentional, are irrelevant to thinking about free will. As first aired at the beginning of this chapter, that is because neither asks a question central to every page of this book: Where did that intent come from in the first place?”³

In short, Tout comprendre, c’est tout pardonner. It’s sound reasoning, but does Sapolsky push that logic far enough? Sure, the Libet experiments can be jettisoned once you realize that people’s intentions aren’t themselves little causeless miracles, but then so can the neuroscience of whatever precedes those intentions—so, why bother with all the neuroscience? He’s so perceptive about the shortcomings of using neuroscience to scrutinize free will in one instance—why not extend that reasoning to neuroscience more broadly?

It’s not like free will skepticism began with Libet studies, but I think the scientific interlopers’ instincts here are somewhat defensible: the science Sapolsky details is a viable onramp to begin questioning the origins of human agency—it’s a powerful way to highlight the problem, and certain ultra-pragmatic people (like Sapolsky) will be much more receptive to a posteriori arguments with scientific hooks rather than a priori philosophizing, which they probably view as linguistic chicanery.

A Scientific Approach

While science might clarify the problematics of free will or be especially persuasive for some people, none of this justifies a scientific monopoly on the topic. But, as the subtitle indicates, Sapolsky focuses on the science. Indeed, he oozes contempt for philosophy, grumbling about having to touch the stuff:

What is free will? Groan, we have to start with that, so here comes something totally predictable along the lines of “Different things to different types of thinkers, which gets confusing.” Totally uninviting. Nevertheless, we have to start there, followed by “What is determinism?” I’ll do my best to mitigate the drag of this.⁴

He also remarks that “In order to prove there’s free will, you have to show that some behavior just happened out of thin air . . . It may be possible to sidestep that with some subtle philosophical arguments, but you can’t with anything known to science.”⁵ Sapolsky’s so anti-philosophical, in fact, that he doesn’t even truly fulfill this reluctant promise to define free will (which is important and doable).

Appeals to science are fair game, and they sometimes enable lucid point-making, but the refusal to leverage philosophy when interpreting science can undercut the potential for insight. Many people view philosophy as a trouble-making or mystifying pursuit, and maybe they presume that excising philosophy will eliminate unneeded disputes, but a lack of disputation isn’t necessarily the upshot of enlightenment—it could also result from parties being unable to even identify disagreements.

Sapolsky most severely hampers his efforts by refusing to clarify what it is about all this determinism that makes free will impossible, besides some allusions to control and luck. For him, I guess the cited science’s ramifications are so plain that res ipsa loquitur. This is a pretty grave blunder: disproving free will requires some argument. Even incompatibilists disagree about exactly why determinism and free will are incompatible, and other philosophers rebut their arguments. Thus, the book reads more like a show of force than an attempt at earnest intellectual combat, like some overconfident diplomat trying to obviate an impending war by giving opposing generals a lengthy tour of their armory: look at all this science—you might as well surrender!

Compatibilism

Sapolsky implies he’s part of a radical minority of freethinkers who don’t believe people have free will, but it’s important to clarify some things here. It’s true that most philosophers aren’t free will skeptics, but the suggestion of radicalism is overblown. Firstly, plenty of past heavyweights and contemporary scholars are/were free will skeptics. Secondly, most of these non-skeptic philosophers are compatibilists, meaning they only believe in a type of free will that’s accessible even when supposing that people’s choices and behaviors are completely predetermined. Much of the Dennett-Harris skirmish referenced earlier centered on whether something of that sort could really count as free will (rather than a genuine dispute over the metaphysical limits of human agency and freedom).⁶ The category of philosophers who believe humans have some kind of free will beyond that (free will that isn’t accessible when supposing determinism)—these are known as libertarians—is also a fringe slice of the profession (though, again, not wildly fringe-y). Even this outline is probably oversimplifying things (there are things like “semi-compatibilists,” for example, that I won’t unpack here), but you get the idea: dispelling this kind of free will may be radical for laypersons, but not for philosophers.

Sapolsky assures readers early on that he’s concentrated on finally defeating these damned compatibilists (philosophers like Dennett), but he doesn’t deliver. I can (I think) discern that he’d endorse to some kind of source incompatibilism (i.e., the view that determinism is incompatible with free will because it precludes someone from being the source of their own actions). Here’s an example of an argument for source incompatibilism from the SEP that resembles Sapolsky’s position (or, at least my reading of it):

1. A person acts of her own free will only if she is the ultimate source.

2. If determinism is true, no one is the ultimate source of her actions.

3. Therefore, if determinism is true, no one acts on her own free will.

Sapolsky’s arguments (which, like a said are mostly facts, innuendo, and invitations for rebuttal more than head-on arguments), focus almost exclusively on showing that (2) is correct and also defusing potential counter-attacks to (2), but here’s what that SEP entry says about (2):

In response to these arguments, compatibilists have denied that… freedom or control require sourcehood. [Compatibilists have only rarely denied Premise 2 of the Source Incompatibilist Argument (McKenna 2008 and perhaps Björnsson & Persson 2012 are important exceptions.]

So, the real controversy is about (1), but (1) doesn’t resemble an especially scientific question. Put differently, compatibilists are largely aware of just how constricting nature is. What Sapolsky repeatedly fails to grasp is that for most philosophers, the question is not how much people’s actions are predetermined, but whether all that determinism really entails the impossibility of free will; or, is there some agentic phenomenon that—even though deterministic—could still deserve to be called free will and/or justify ascribing people moral responsibility? So, every time a scientist runs on stage to detail just how extremely determined we are, compatibilists are going to be unmoved.

The misfire is apparent in his topic selection too, as he devotes substantial energy to scientific concepts (like chaos, emergence, and quantum indeterminacy) that people float as vehicles for trying to evade the logic of determinism. The project is still edifying, but it’s not charging headlong into the fray with compatibilists. Comparing Sapolsky’s book with, say, McKenna and Pereboom’s Introduction to Free Will and Moral Responsibility, there’s shockingly little overlap. Mainline topics go largely undiscussed by Sapolsky (the Principle of Alternate Possibilities, Classical Compatibilism, Manipulation Arguments, Reason-Response theories, etc.).

Conversely, if you look at the Stanford Encyclopedia of Philosophy’s entry on Compatibilism mentioned supra, there’s no discussion of reduction/emergence or chaos theory, yet these phenomena receive lengthy treatment by Sapolsky, and the quantum mechanics chapters are plainly about indeterminism (and therefore not about Compatibilism either). So, it’s tough to view Sapolsky’s effort as earnestly engaging with compatibilist theories beyond a few glancing blows. Instead, he concentrates on grappling with scientific avenues toward a hefty version of free will that he views to be legit; consequently, the spectre of strawmanning haunts the book throughout.

I greatly sympathize with the outlook that Compatibilism is just confused sophistry, but unless Sapolsky’s science gets wired up to some philosophical arguments, it’s merely orthogonal to most of the controversy. I see no great sin in scientists trying to squeeze a bit more lab equipment onto the debate stage, but trying to evade philosophy completely was overambitious.

Conclusion

So, can science disprove free will? Yes and no. Science can rule out certain versions of free will if you’re inclined to go about it that way, but you can’t really apply the science without getting your pragmatic hands all covered in totally impractical, high-grade, uncut philosophy. Maybe the science Sapolsky presents should easily disillusion folks from some naive intuition that people can really be causa sui, but, then again, we didn’t need Libet studies or cutting-edge physics to figure that out; here’s a popular Nietzsche quote about libertarian free will that easily predates Libet studies:

The desire for "freedom of the will" in the superlative metaphysical sense, which still holds sway, unfortunately, in the minds of the half-educated; the desire to bear the entire and ultimate responsibility for one's actions oneself, and to absolve God, the world, ancestors, chance, and society involves nothing less than to be precisely this causa sui, with more than Münchhausen's audacity, to pull oneself up into existence by the hair, out of the swamps of nothingness.⁷

But then who this book is for, given Sapolsky’s unwavering scientific approach? A book on free will for people who dislike philosophy is a somewhat self-defeating sales pitch. Maybe it’s for the professional scientist, who wants to see what philosophy could look like if they finally ousted the humanities profs from academia, or maybe an engineer or a doctor who possesses an ineluctably pragmatic temperament, but in some twist of fate, is forced to learn about free will. It’s unclear. A sizable fraction of people would greatly prefer reading Sapolsky to something more philosophical, but would those people read a book about free will to begin with?

In fairness, the book possesses some gems—his discussion of whether our lack of free will needs to remain an arcane secret to prevent anarchy is strong work that benefits from his empirical approach. And Sapolsky’s philosophical-hands-tied-behind-his-back technique succeeds in dodging a pointless retracing of dusty philosophy—it just doesn’t manage to entirely circumvent the inconvenience of those complications. It’s a Chekov’s gun of a book, ultimately. He promises to define free will but doesn’t; he promises to focus on compatibilism but whiffs; he, at least tacitly, promises to disprove free will, but never truly presents an argument for that.

But just because the book doesn’t achieve its aims doesn’t mean it doesn’t achieve anything. Sure, Sapolsky doesn’t deliver on his promises, but that’s partly because he promises too much. Trying to disprove all versions of free will—over-sophisticated, scientifically confused, and hopelessly naive—all in one sweep and only using science, is too steep a climb for any book. It’s better to think of Sapolsky’s effort as a tour d’horizon of scientific concepts that could be relevant to free will discussions rather than the masterwork of someone applying a blowtorch to the sophistry and verbal decadence of cloistered philosophers. He doesn’t fully point out that the emperor has no clothes, but he still manages to show that the emperor hasn’t needed to do laundry in a suspiciously long time.

1. You can read Harris’s rebuttal here. Harris has sparred with other free will scholars like Tamler Sommers on this, too, and eventually circled back with Dennett on the topic a few years later.

2. Theological versions of this also exist (viz., if God is omniscient and therefore knows the future, how could you be free?)

3. Sapolsky, Robert M. Determined: Life Without Free Will, Random House (2023): 40.

4. Id. at 14.

5. Id. at 83.

6. Dennett put his counterargument like this: “When we found out that the sun does not revolve around the earth, we didn’t then insist that there is no such thing as the sun (because what the folk mean by ‘sun’ is ‘that bright thing that goes around the earth’).  Now that we understand what sunsets are, we don’t call them illusions. They are real phenomena that can mislead the naive.”

7. Nietzsche, Friedrich. Beyond Good & Evil: Prelude to a Philosophy of the Future, Vintage (1989): 28.