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A Physicist on Free Will

by Bill Meacham on September 5th, 2023

Last time I criticized some of Sartre’s ideas about free will but didn’t address whether we even have free will in the first place. Sartre thinks we do, but his view is not shared by everyone. In particular, many think that we have no free will because the world is entirely predetermined. This idea has been set forth recently by Sabine Hossenfelder, a particle physicist and a popularizer of physics for the layperson.

Book cover - Existential Physics

I am not qualified to evaluate her competence as a physicist, but I can attest that her recent Existential Physics is a highly readable and entertaining account of what physics tells us about a number of issues. One of them is whether we have free will. She asserts that we do not because the world is deterministic. Our choices and decisions she says, although seemingly made freely by us, are actually the result of interactions of the physical elements of which we are composed, and these elements obey fixed laws, so our actions and decisions are predetermined. Let’s go through her argument.

We start with the observation that the world contains regularities:

We implicitly assume nature is uniform, constant, and reliable in its proceedings. The laws of nature don’t suddenly change. If they did, we wouldn’t call them laws.(1)

Now, there are some philosophical questions about what the laws of nature really are. Are they just simple regularities? Are they elements in deductive theories that enable us to make accurate predictions? Are they somehow metaphysically necessary regularities?(2) For our purposes, we don’t need to decide. They enable us to understand and control our environment, and that’s good enough. In practice we rely on the assumption that nature is predictable, and so far that assumption has worked out just fine, so we continue to rely on it.

The next step in the argument is called “reductionism” or “materialism.” It’s the idea that, as Hossenfelder says,

things are made of smaller things, and if you know what the small things do, then you can tell what the large things do. There is not a single known exception to this rule. … The behavior of a composite object (for example, you) is determined by the behavior of its constituents—that is, subatomic particles.(3)

And that’s that, according to this argument. All of our behavior, including our decisions, is determined by inexorable laws of nature because the behavior of big things is determined by their constituent small things, and the tiniest things we are made of obey fixed laws.

Except they don’t. Or rather, they do, but some of the laws are only probabilistic. At the level of very tiny things, the quantum level, events are indeterminate. We can’t predict the outcome of a single quantum event, only its statistical probability. Hossenfelder, of course, recognizes this fact—”The future is fixed,” she says, “except for occasional quantum events that we cannot influence.”(4)—but thinks it doesn’t matter. We can’t change the laws of nature, and we can’t influence quantum events, so we have no choice in what happens.

Her dismissal of occasional quantum effects is crucial to her argument, but it is a mistake. At the macroscopic level of everyday experience, certainly, whatever quantum events that may happen have such a minuscule effect that they are safely ignored. But quantum events happen in the brain, as she recognizes:

… deep down all our brain processes are quantum processes ….(5)

She doesn’t go into details, and there is more than one theory about such processes. Roger Penrose and Stuart Hameroff cite quantum collapse in microtubules inside neurons.(6) Henry Stapp cites calcium ions in quantum-scale neuronal channels.(7) Whatever the details, quantum effects do take place in our brains. Of course submicroscopic events trigger larger events, which are then causally determined. But the initial events, the beginnings of chains of causality, are indeterminate. That means that our thoughts and behaviors are not fully determined in advance.

Does that indeterminacy mean that our will is free? Hossenfelder thinks not. She says

… there is no “will” in quantum randomness ….(8)

In this she agrees with psychologists Joshua Green and Jonathan Cohen, who say

If it turns out that your [actions are] completely determined by the laws of physics, the state of the universe … and the outcomes of myriad subatomic coin flips, your [action] is no more freely chosen than before. Indeed, it is randomly chosen, which is no help ….(9)

But neither she nor they are looking for will in the right place. The concept of will does not apply to submicroscopic physical events or even to macroscopic entities like neurons. The concept of will applies at a higher level of explanation, namely that of persons. By a “higher level of explanation” I mean what Hossenfelder calls an “effective model.”

An effective model is one that leaves out irrelevant detail. Her analogy is a topographical map with extremely fine detail, having contour lines at a scale of an inch or less of elevation between them, which would show individual cracks and pebbles. You could then zoom out to show the contour lines at 5 or 10-foot intervals of elevation or even more. At a zoomed-out level you lose a lot of detail, but the 5-foot scale would be more useful for planning drainage in a landscape design, and at a 100-yard scale you could plan a hike through mountainous terrain. You pick your scale according to what you want to accomplish.

At these zoomed-out levels

… you have what physicists call an effective model. This model is not fundamentally correct [because some information is left out], but it is good enough at the level of resolution you are interested in. …

It is typical of an effective model that the objects and quantities central to it are not the same as those in the underlying theory; they usually do not even make sense in the underlying theory.(10)

That’s the case with human will, whether free or not. When we consider human action and will, we find things that are best described by using a different effective model, that of personal agency. The patterns of beliefs, desires, aversions and intentions that we ascribe to ourselves and others are at a higher level than the individual neural events which underlie them, and they obey different laws. One of the working assumptions of personal agency is that people can make free choices. The fact is, we all act as if we have free will, regardless of what we say we believe about it. We don’t try to convince a customer to buy our product or a friend to go with us to a concert by altering their brain chemistry. Instead we appeal to their motives and desires, perhaps to their pride or some other emotion, to convince them to make the choice we want.

Pragmatically it makes sense to consider our will as free, regardless of the subatomic and neural events that underlie our behavior. I suspect Hossenfelder would agree with me so far. The agential model is good enough at its applicable level of resolution. But, she would ask, is our will really free? That is to say, is there a way to calculate, deduce or conceptually connect the low level to the high in a rigorous way? Reductionism means that

the behavior of an object can be deduced from (“reduced to,” as the philosophers would say) the properties, behavior, and interactions of the object’s constituents …. (11)

Can we reduce, she would ask, agential properties to those of subatomic quantum events?

Not at present, certainly, and I don’t know whether we will ever be able to. But there is a way to think about the issue that nevertheless seems plausible. Hossenfelder would call this way of thinking “ascientific,” meaning that the scientific method can’t tell you whether or not it is correct.(12) I call it “metaphysical,” meaning that it goes beyond physics to deal with things that physics can’t.

My ascientific, speculative, metaphysical view is that quantum indeterminacy in the brain enables our will to be free. The crux is that what matters is not the outcome of a single quantum event, but the overall pattern of many of them. What appears to be random when you look only at individual events reveals patterns when you look at them in aggregate. Micro-units of quantum indeterminacy cohere into larger arrangements that are not random. Consider a pointillist painting, which consists of distinct dots of pigment. If you look at it up close, all you see is random dots. When you view it from afar, you see identifiable forms and shapes, recognizable objects and patterns. In our case, these patterns are agential.

But what causes (if that is the right word) random events to cohere into agential patterns? What explains such behavior? The process metaphysics of Alfred North Whitehead provides the answer.

I have written about Whitehead’s metaphysics elsewhere, so I won’t go into a lot of detail here. Please refer to my book How To Be An Excellent Human and my essays “Dead or Alive?” and “A Whiteheadian Solution to the Combination Problem“. In brief, Whitehead agrees with modern physics that things are made of smaller things. His insight is that the smallest of them, which we refer to as subatomic “particles,” are better thought of as a series of events, which he calls “actual occasions;”(13) and these events are not only detectable by other entities but are also, in a minimal way, aware of their surroundings. This theory is a variety of panpsychism. As I like to say, everything that has an outside has an inside too.

Whitehead intends his categories of explanation to apply both to the quantum level of reality and to the world revealed by our unaided senses. In our everyday world it is undeniable that, unless we are asleep or sedated, we are aware of our surroundings and remember our past. And, of course, others can be aware of us. So Whitehead posits that the smallest entities are also, in a way, aware of their surroundings and of their own past as well as being detectable by other entities. Whitehead calls them “occasions of experience.”(14) The tiniest actual occasion is structurally similar to a moment of rich human experience, albeit in a primitive, attenuated form. What we think of as a particle is actually a temporal series of these actual occasions. A single electron is a series of momentary electron-occasions that form an enduring object much like the momentary frames of a movie form a continuous picture. And that enduring object experiences its world.

Yes, this idea is quite anthropomorphic, but that’s a feature, not a bug. Instead of trying to figure out how conscious beings arise from dead particles, we assume that it works the other way around and the particles are minimally conscious.

So let’s get really anthropomorphic. Imagine that you are a calcium ion in a neuron just arriving at a vesicle full of neurotransmitters.(15) Do you proceed to strike (i.e., be detectable at) a site that will trigger the release of neurotransmitters to the synaptic cleft? Or do you strike somewhere else? Or do you just hang out and wait for a bit? It depends on how you feel. Just as a person might pick vanilla or strawberry ice cream depending on nothing more than what they feel like having in the moment, you as a calcium ion just do what you feel like doing.

And what determines what you feel like doing? The feelings of all the other quantum events and enduring objects in your vicinity.

A critical part of Whitehead’s account of how reality works is that feelings “leak” from mind to mind. Whitehead has a technical term—he calls it “prehension”(16)—for the process by which each actual occasion comes into being by incorporating into itself elements, both physical and mental, of its predecessors and its surroundings. The upshot is that an elementary particle is not like a little billiard ball being pushed around. It is more like a succession of tiny agents deciding what do next. The mental aspect of these tiny agents, these actual occasions, combine into a greater mental whole just as the atoms, molecules and cells combine into a greater physical whole. And that greater whole, especially in the case of us humans, obeys agential laws as well as physical ones. The beliefs, desires and choices of the whole exert a downward influence on the tiny events that make it up. Although the neural events are individually random, as a whole they conform to the larger agential pattern.

Hossenfelder might well sneer at this idea. She says “If you say ‘holism,’ I hear ‘bullshit.'”(17) But despite this account of free will being not experimentally confirmable there are reasons to believe it true.

Crucially, this account is not in conflict with the physics of elementary particles. Any individual quantum event in a neuron is indeterministic. Given the possibility of causing a nerve impulse to fire, it might and it might not; we can’t tell in advance (even if we could observe it without destroying the organism it’s a part of, not to mention causing an unintended collapse of its wave function). Only when we look at the interaction of many of them do we find patterns that make sense in agential terms, including the belief that our will is free.

This account, bare bones as it is, conflicts with no physical laws, contains no internal contradictions and supports the very useful attribution of mental states, desires, beliefs and free will to ourselves and other people. Thus it is reasonable to believe it.

Our will is indeed free. Now it is up to each of us to figure out what to do with it.

(For a more detailed account how our will is free, please see my free ebook, How To Exert Free Will.)


(1) Hossenfelder, Existential Physics, p. 38.

(2) Bain, “Laws of Nature.”

(3) Hossenfelder, p. 82.

(4) Hossenfelder, p. 125.

(5) Hossenfelder, p. 113.

(6) Hameroff, “Consciousness, Cognition and the Neuronal Cytoskeleton.”

(7) Stapp, Mindful Universe, pp. 30-32. I discuss Stapp’s theory in more detail in Meacham, “The Quantum Level of Reality.”

(8) Hossenfelder, p. 130.

(9) Greene and Cohen, p. 1777.

(10) Hossenfelder, p. 85.

(11) Hossenfelder, pp. 82-83.

(12) Hossenfelder, p. 113.

(13) Whitehead, Process and Reality, p. 32.

(14) Whitehead, Adventures of Ideas, p. 221.

(15) Meacham, “The Quantum Level of Reality.”

(16) Whitehead, Process and Reality, pp. 28-29, 32, 35.

(17) Hossenfelder, p. 83.


Bain, Jonathan. “Laws of Nature.” Online publication as of 1 September 2023.

Greene, Joshua and Jonathan Cohen. “For the law, neuroscience changes nothing and everything.” Philosophical Transactions of the Royal Society of London B (Biological Sciences), Vol. 359 No. 1451, pp. 1775-1785. Online publication as of 7 March 2013. Available at as of 3 September 2023.

Hameroff, Stuart. “Consciousness, Cognition and the Neuronal Cytoskeleton – A New Paradigm Needed in Neuroscience.” Frontiers of Molecular Neuroscience, 15:869935. doi: 10.3389/fnmol.2022.869935. Online publication as of 1 September 2023.

Hossenfelder, Sabine. Existential Physics: A Scientist’s Guide to Life’s Biggest Questions. New York: Viking, 2022.

Meacham, Bill. How To Exert Free Will. Available online at

Meacham, Bill. “The Quantum Level of Reality.” Online publication

Stapp, Henry P. Mindful Universe: Quantum Mechanics and the Participating Observer. Berlin: Springer-Verlag, 2007.

Whitehead, Alfred North. Adventures of Ideas. New York: The Free Press, 1967.

Whitehead, Alfred North. Process and Reality: An Essay in Cosmology. New York: Harper and Row Harper Torchbook, 1960.

From → Philosophy

  1. Thanks for your latest essay. I would like to agree with what you said but I cannot. Try as I might, I am pre-determined to think otherwise. If I had a choice, I would agree. But alas!

  2. Parmenides permalink

    Arguments against determinism:
    1. Quantum mechanics
    2. Chaos theory

    Of the two, chaos theory is easier and more convincing, although quantum mechanics might be more fundamental. I have friends who work (or have worked) on Newtonian mechanics. It is an open problem whether the Solar System is stable. In the future, will the planets possibly go on wild excursions a la Velikovsky? Nobody knows. So much for “if you know how the small things work you know how the bigger things work.” I’m surprised that an actual physicist is writing in favor of determinism in this century.

    In about 1969 I had (on LSD) what I thought at the time was a brilliant insight: even an electron has some consciousness, specifically, enough to exercise free will about when to come down from an excited state in a hydrogen atom. As many electrons make their choice, we do see statistical regularities, of course, just as humans making free choices show statistical regularities. However, I had enough sense to keep this wild idea to myself over the years.

  3. It’s interesting how so many people who argue against free will, also can’t see the point of punishment. I think Kant was on the right track when he argued that free will could not be understood scientifically. Free-will or the human will are not physical things or processes. We can experience free will in our own actions but we can’t observe it in other people, other than by imagining ourselves in their place, or by observing its absence (when people are physically forced to do things, or they are incapacitated through drugs, hypnosis, or delirium) Kant’s concept of “things-in-themselves” is a non-starter because it is speculation with no possible evidence that could either support or refute it. It’s better to understand free-will as an integral part of all human moral systems. Every moral system is a self-organized way of regulating human behaviour which requires each person to agree to be bound by moral rules, and to be more or less guided by moral ideals. By living in a human society we each implicitly agree to follow the moral rules. In a moral system we assign guilt to those who break the moral rules and we usually believe that they deserve to be punished. This is based on the principle of free-will. We believe that if the person broke the moral rule but could have done otherwise, they are guilty of a moral crime and ought to be punished. There is no point in punishment if people actually do not have free will. Punishment doesn’t have to be rigidly applied but can depend not just on the gravity of the offence but also on extenuating circumstances,justifiable excuses, and the intentions of the perpetrator. Punishment for moral offences can range from being the subject of gossip, being publicly ridiculed, shunned, exiled, imprisoned, and executed. Enforcement is the lynch pin of a moral system because it is what keeps the system working in the face of inevitable transgressions. Without enforcement, people can see that other people can literally get away with murder, and they come to reject moral obligation and the system breaks down into every man for himself. We take for granted that we live under a moral system and that we have free will. Those who don’t believe in free will misunderstand the nature of morality and it’s impossibility in the absence of enforcement.

  4. George H permalink

    Thanks. She should stick to particle physics.

    I agree we appeal to “motives and desires”, and of course “emotions” as well. But, when you write a book about philosophy you need to appeal to reason.

    What is the lowest level we ground this determinism? Could we reason at that level?

    We reason about the contents of our neural circuits. What Tse calls patterns of energy. We certainly do not reason with neurons let alone elementary particles.

    One more point. I don’t see a need for anything additional to explain consciousness. Our intentionality is embedded in the contents of neural circuitry. I personally see no need for pan-psychism; I prefer emergence.

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