Does Quantum Mechanics allow for Free Will?

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Do the laws of physics rule out free will? Neuroscientist Kevin Mitchell has a recently argued (paper and blog post):

  • If the laws of physics are deterministic, then free will is ruled out
  • If the laws of physics are indeterministic, then this makes room for the reality of free will.

It’s a really interesting paper but I have some disagreements, which I would like to outline here.

A quick preliminary remark: there is a huge debate in philosophy as to whether or not human freedom is compatible with determinism (we can define determinism as the thesis that the initial state of the universe, in conjunction with the laws of nature, determine everything that will happen subsequently). Compatibilists believe is that free will and determinism can happily co-exist. Mitchell is well aware of this debate, and briefly motivates his commitment to incompatibilism: that view that if the universe is determined, we’re not really free. For the purposes of this blog post I will assume incompatibilism.

Given the assumption of incompatibilism, Mitchell argues that the way to avoid the clash between freedom and indeterminism is to embrace the indeterminism entailed by many interpretations of quantum mechanics. Now, many have pointed out that mere randomness isn’t what we need to make sense of freedom, and Mitchell acknowledges this. But he thinks that the absence of total determinism in fundamental physics provides some ‘causal slack’ that mental processes at the neurophysiological level can then take advantage of:

“The inherent indeterminacy of physical systems means that any given arrangement of atoms in your brain right at this second, will not lead, inevitably, to only one possible specific subsequent state of the brain. Instead, multiple future states are possible, meaning multiple future actions are possible. The outcome is not determined merely by the positions of all the atoms, their lower-order properties of energy, charge, mass, and momentum, and the fundamental forces of physics. What then does determine the next state? What settles the matter?”

Mitchell’s answer this posed question is the agency of the organism: physics leaves certain options open, the organism then decides from among those options.

It sounds intuitive, but I don’t think this strategy ultimately works. Even among indeterministic interpretations of quantum mechanics, although the physics doesn’t conclusively settle what will happen, it does determine the objective probability of what will result from any given physical circumstance. Although we can’t predict with certainty, say, where a given particle will be located when we make a measurement, the Born rule tells us, for any given location in the universe, precisely how likely we are to find the particle in that location. It’s not determinism, but it’s not a ‘free for all.’

Mitchell worries that if the physics determines what I’m going to do, then I’m not really free. But physics determining the objective probability of what I will do is no less constraining. If whether I water Susan (my Madagascan dragon tree) is really up to me – in the strong incompatibilist sense – then surely the physics can’t fix how likely it is that I will water Susan. If it’s just totally up to me, then it could go either way depending on my radically free choice.

Here’s a little thought experiment to make the point clear. Take the moment when I’m about to decide whether or not to water Susan. Let’s say the Born rule determines that there’s a 90% change my particles will be located in the way they would be if I watered Susan and a 10% chance there’ll be located in the way that corresponds to not watering Susan (obviously this is a ludicrously over-simplistic example, but it serves to make the point). Now imagine someone duplicated me a million times and waited to see what those million physical duplicates would decide to do. The physics tells us that approximately 900,000 of the duplicates will water Susan and approximately 100,000 of them will not. If we ran the experiment many times, each time creating a million more duplicates and waiting for them to decide, the physics tells us we would get roughly the same frequencies each time. But if what happens is totally up to each duplicate – in the radical incompatibilist sense – then there ought to be no such predictable frequency. The number that do and don’t water the plant should change each time, as the radically free choices of each individual varies.

In other word, indeterministic quantum mechanics doesn’t provide the kind of causal slack Mitchell is seeking. The problem is that objective probabilities constrain our choices as much as deterministic laws. After all, a deterministic law is just a law that yields an objective probability of 1 that a given outcome will occur.

All is not lost, however. I think Mitchell is conflating two claims:

  • The laws of physics are deterministic
  • The universe as a whole is deterministic

How could these come apart? They come apart if the laws of physics are ceteris paribus laws, i.e. laws that tell us what will happen in the absence of other causal influences. On this interpretation of physical law, the probabilities yielded by the Born rule are the objective probability of what will occur in the absence of some other causal influence. Such other causal influences might include the kind of irreducible causal powers Mitchell believes reside at the level of neurobiology. Mitchell seems to be concerned to avoid a violation of the laws of physics. But if the laws of physics are ceteris paribus laws, then higher-level causal powers should be thought of as complementing the laws of physics rather than contradicting them. If physics basically tells us ‘X will happen unless there are some higher-level causal forces,’ and X doesn’t happen precisely because there are higher-level causal forces, then nothing occurs that is inconsistent with physics.

It does not follow that there are no empirical challenges for a proponent of incompatibilist free will. Some philosophers have argued that we have strong empirical grounds for thinking there are no irreducible causal influences of the kind Mitchell believes in, that everything that happens at higher levels can be reduced to the causation we find in physics. But this is an empirical question about neurobiology. My point here is just that the question of whether the laws of physics are deterministic has no bearing on the question of whether the universe as a whole is deterministic, and hence no bearing on the question of whether or not we have free will.

The Author

I am a philosopher and consciousness researcher at Durham University, UK. My research focuses on how to integrate consciousness into our scientific worldview.


  1. cadmar larson says

    I enjoy Stephen Wolfam view that we are in an irreducible computational universe. In the Susan thought experiment, what is missing is that the program would have to start from the very beginning of the universe to get to the situation in which you are deciding to water or not. Will rerunning the program get you to the same individual and to the same situation? Stephen claims there are too many inputs to reach that and this is the natural law of universal computation.

    My take is on that there is a force that is moving all the objects and somehow this force is connected to us, or we are connected to it that gives us this ability to be outside the physical restraints of the universe. This gives us the ability to understand as understanding is the means of looking outside and seeing the entire picture.

  2. Hi Philip,

    Reading along, I was going to suggest a similar workaround for Mitchell, but I wouldn’t put it quite as you do.

    I would not disginguish the determinacy of the laws of physics from the determinacy of the universe, I would distinguish the determinacy of the laws governing the behaviour of particles as observed in experiment to date (the micro-physical laws) from the determinacy of the laws governing the higher-level causal forces, if there are any.

    Personally, I don’t think it is coherent to suppose that anything in nature behaves as an outlaw. The laws of physics just describe how nature behaves. If something appears to behave contrary to the laws of physics, then that just means we don’t understand the laws of physics. The idea that anything *just happens* without any sort of rules or mechanism to account for how it happens or even according to what probability distribution, is to me the essence of supernaturalism and little more than an excuse to stop thinking.

    In a sense, these higher level laws might allow Mitchell some wiggle room, because it is conceivable that the laws of physics allow particles in a brain to behave differently from particles in a double-slit experiment in a way that has not yet been uncovered by scientists (but presumably could be, in principle). But on the other hand, by my lights, it would still mean that those higher level causal forces are still describable by law, and so ultimately no less mechanical than the micro-physical laws. If the micro-physical laws rule out incompatibilist free will, then the same goes for the higher level laws.

  3. High Mass Particle says

    If a particle is a baby universe then it would really be very complex even if they externally behave in very simple ways — a sleeping person has very simple external behavior but internally a lot of very complex things are occurring both physically and mentally (dreaming).

    If particles are sleeping then their external behavior might just revert to default mode which is simple and mostly predictable (quantum mechanics). It is only with high mass particles or quantum coherent molecules that quantum mechanics can transition to libertarian free will physics.

  4. One might also add that it’s standard for physicists themselves to take a ceteris paribus view of physical theories! For example any physicist will tell you that the known laws of quantum mechanics *become invalid* when gravitational forces are large.

    Of course many physicists believe their field will eventually discover an absolute (and fully reductionist) set of laws, so there’s still a wide philosophical gulf between them and conscious realism etc. My point is just that the ceteris-paribus intellectual framework is already well established and the best physics we have today, including QM, uses it.

    The idea that an elegant set of laws can describe things very precisely but break down when circumstances change, is not a stretch at all. It’s standard.

  5. Lee Roetcisoender says

    What I consider to be reckless as well as intellectually immature is this notion that there is such a “thing” as LAW or RULES in the first place. It’s like Disagreeable Me pointed out: without any sort of rules, there has to be another mechanism to account for causation. So, if there are no magical, mysterious RULES or LAWS commanding unwavering, unquestioning obedience from its unknowing unsuspecting subjects; then what are those other mechanisms?

    Intelligence should be the final arbiter on such matters, but intelligence has not evolved to the point where it can be used effectively for purposes other than survival. In laymen’s terms this means that intelligence is fundamentally ego centric. As a result, our species is incapable of setting aside the solipsistic self-model and thinking outside that box of self in an objective manner. Intellectual immaturity is the very reason why our experience is a subjective experience instead of an objective one.

    One should be compelled to consider that our own immune system is much more intelligent than the system of mind, at least the immune system has the capacity to be objective. And ironic as it may seem, in spite of the immune system’s superior intelligence, we do not consider the immune system to be conscious. Homo Sapiens may be a very clever species, but at our core we are just another dumb animal.

  6. cadmar larson says

    Laws and Rules of Nature are just observations that fall under certain conditions. Is very convenient and a shortcut without going into repeating details, as from just mentioning the laws, we know exactly what is being stated. That is it and nothing inherent to them! The immune system is stuck within these observations and has no choice in its reactions: if A happens then it does B; if A does not happen, then it does C. Otherwise, nothing gets done and there is no consistency. Human consciousness has the ability to understand and to be outside this restraint of having no options. Zeno’s insight that walking from point A to point B and each successive step is only half-way there, comes from realising he will never make it to point B, even though he will be almost touching it! A turring machine will continue to churn out the steps, getting closer and closer without realising and understanding that it will never reach point B! The computer is under the restraint of having no options and will continue forever until it is arbitrarily shut off. The mind understands this!

    • Lee Roetcisoender says

      But does the mind understand that: “Intellectual immaturity is the very reason why our experience is a subjective experience instead of an objective one.”

  7. cadmar larson says

    Intellectual immaturity is unable to answer as all answers will not have all the information and data for it to make an accurate answer. Intellectual immaturity can only give “gut feelings”, “approximations”, “a belief arising from the path I am on”.

    • Lee Roetcisoender says

      “Intellectual immaturity is unable to answer as all answers will not have all the information and data for it to make an accurate answer.”

      Nice tautology cadmar. Intellectual immaturity is unable to answer not because all the information and data is unavailable; it cannot answer because the data and information that is available is “subordinate” to what the solipsistic self-model says it is, (AKA, subjective experience).

      Intellectual immaturity is an intrinsic genetic defect built into the system of mind expressed as a self-serving solipsistic self-model. Intellectual immaturity places the solipsistic self-modle first in a self-serving, self-perpetuating hierarchy, a hierarchy that irrevocably reduces to the solipsistic self-model being sovereign. This type of immature rationale just keeps going round and round and round and round and round…….

      Conclusion: “…intelligence has not evolved to the point where it can be used effectively for purposes other than survival.”

  8. cadmar larson says

    Our interpretation of data depends on assumptions. Assumptions are what we do not know, but is our best guess from previous experiences, experiments, and rules of logic. For example, the orbits of planets around the sun. Newton assumed that the planets have some inner force that attracts each other (graviton), similar to a magnet. Einstein came along with another assumption that it is the spacetime that creates the gravity.

    So, what do you assume to be the difference between a subjective experience and an objective experience? You are making an assumption and this assumption is either right, or wrong. Either answer will lead one down a certain path of understanding and logic. Immaturity is defined as having assumptions and any assumption always has two different paths.

  9. Lee Roetcisoender says

    “So, what do you assume to be the difference between a subjective experience and an objective experience?”

    A subjective experience is when “Reality” (whatever that is) is subordinate to the solipsistic self-model. An objective experience is when the solipsistic self-model is subordinate to “Reality”.

    Every system in our physical universe including the physical system of mind has an objective experience. But only the physical system we know as mind has the intrinsic power and freedom to disrupt that ubiquitous dynamic. Like all other physical systems, mind is finely tuned and well suited for survival; and like all physical systems, mind has only a limited degree of self determination within an otherwise deterministic system.

  10. cadmar larson says

    Philosophy is about examining with a fair, and hopefully, position that one would be more interested in finding one’s position as being wrong, rather than as being right because when a philosopher realises oneself is wrong, then at that moment, real and deep learning takes place. To get to this deep level of understanding, learning requires an exchange of ideas and hopefully, the examining of assumptions. You never state the assumptions you are making for you to say with full accuracy that the mind is part of the physical world and thus is deterministic. You do not explore your assumptions that you have for you to reach this conclusion.

    • Lee Roetcisoender says

      “You do not explore your assumptions that you have for you to reach this conclusion.”

      I find it ironic that your (subjective) conclusions are based upon information and data that I have not provided therefore, in addition to your dialectic shortcomings you must be telepathic. Real and deep learning takes place when one is intelligent enough to recognize that one’s experience is an objective experience and not a subjective one.

      “(human)…intelligence has not evolved to the point where it can be used effectively for purposes other than survival.”

      Be at peace my friend

  11. Hi Phillip, I appreciate your thoughts. Reminds me of much of what Lewis wrote in his book “Miracles”. I’m not sure whether he’s right that free will is evidence of the miraculous per se, but it does seem that if free will truly exists (I’m not sure), there must be forces outside the laws of physics that allow for that.

    On another note, I discovered your blog through your recent Scientific American article on our improbable existence. I’ve been thinking a lot about this topic (both pre- and post- reading this article), and respectfully disagree with your reasoning in the article.

    You seem to confuse 3 different types of probability:
    1. the probability that an event will occur in a specific attempt
    2. the probability that an event will occur, period
    3. the post-event “probability” that it has occurred in a specific attempt

    A lot of it boils down to whether other “attempts” are relevant or not. You choose good examples of scenarios where they are not. But I could just as easily come up with scenarios where they are.

    For example, instead of the inverse gambler’s fallacy as presented (where the only relevant event is the single time the gambler roles when you happen to walk in), say that the casino gives anyone who rolls a double six a special crown to wear, to show that they won. Now, you walk into a casino and see someone wearing such a crown. It would be logical to assume they probably have been playing for a long time (especially if, say, we use 1 in a million odds instead of 1/36). While each time they play has zero bearing on the chances their NEXT role will be a win (independent events), the more they play, the higher their chances that they do win, period (law of large numbers).

    Using the monkey typewriter example, the author is of course right that the presence of other monkeys has no bearing on whether the one monkey is writing good English. But let’s say this scenario: You are told there will be an unknown number of ghost monkeys overnight that type, and if any happens to type English, they will materialize and be visible to you. You wake up and see a monkey typing English. It would be perfectly logical to say it’s likely there are a very large number of monkeys present. Their presence does not affect that particular monkey’s skill/luck; but the presence of many does mean it is more likely there will be one that types English, period, which is what you observe.

    That last sentence may seem contradictory when one overthinks it, but this gets to the 3 types of probability I mentioned. A very simple example would be rolling a 6-sided die.

    1. what are the chances a given roll is a 1? 1/6
    2. If I roll it a million times, what are the chances I get at least one 1? 100%
    3. Say I do roll it a million times, and on the 12th attempt get a 1. I excitedly call a friend. They try to tell me they don’t think I actually got a 1 on the 12th time, because that is an improbable outcome (1/6), and the number of times I otherwise role has no bearing on the outcome of the 12th attempt. Of course, this fails to account for the fact that once an improbable event has occurred, it’s probability is now 100% (the a priori probability is now meaningless, a moot point). And with enough attempts, it is 100% likely it will happen (once again, regardless of the a priori probability), even while still unlikely it will happen (a priori) at any given attempt. And if I only phone my friend whenever I roll a 1, each time my friend gets a phone call he can be 100% sure an unlikely event just occurred, without being at all surprised about it.

    Similarly, with the universe question, I don’t think anyone postulates that having other universes “out there” has any bearing on the probability THIS universe supports life. From that lens the other universes are completely irrelevant, and all that matters is the a priori probability for this given universe/attempt. But, the whole point is that if you take the lens of an infinite (or very large) number of universes, the a priori probability of supporting life (by definition #1) becomes irrelevant as the probability of life being supported, period (#2 definition) approaches 100%, and then the observed supporting of life (#3 definition) is rather expected. And in that case, just as it would be flawed for my friend to disbelieve the plausibility of I having rolled a 1 on the 12th time (after it occurred), it would be flawed for us to think it improbable that our particular universe happens to support life, now that we are aware it is one that does so.

    I’m not saying there necessarily are multiple or infinite universes, only that the logic has merit to it.

    (I think an even more compelling argument for parallel universes though is on the quantum level: what if rather than wave functions collapsing (which we seem to observe but there is no logical consistency in why that should be the case), what happens in interactions is not a collapse of the wave but rather entanglements of waves, with both/all possibilities and combinations simultaneously existing in parallel. So then the Schrodinger equations are universally consistent, rather than inexplicably collapsing. I’m no physicist though, but that’s my understanding of how some of them approach it).

  12. Rafael A Bernal says

    Re your SciAm article on Our Improbable Existence, I really liked it, perhaps out of an aversion to multiple universes. One point I have never seen is this: Saying that we live in an improbable universe is like saying that the jackpot winner is absurd because it’s so improbable that that specific number would come up. Turning the question around, I’d say that, if a universe is born with one law: Emergence, it will evolve perhaps to reach consciousness, like ours. Life and intelligence do not necessarily have to be like us and neither the universe has to be as this one in order to evolve.

  13. Joseph Sabella says

    I believe we have a partial, probabilistic “free will,” in contrast to a total “free will.” I base my belief on the assumption that we emerged from and are immersed in a universal quantum field, the quantum vacuum, and that just as the Totalitarian Principle moderates the quantum vacuum, I believe the Totalitarian Principle also moderates our “free will.” Here’s why I believe this.

    According to physics, the quantum vacuum is a field of quantum possibilities, with each quantum possibility possessing some probability of eventually transitioning to an actuality, such as our universe, providing that transition is not forbidden by a few conservation laws, such as conservation of energy, charge, or momentum. Consequently, even possibilities with a low probability of transitioning to actuality must eventually transition. In 1956, physicist Murray Gell-Mann named the eventual transition of quantum possibilities to actualities, the Totalitarian Principle, and he concisely stated it as, “Everything not forbidden is compulsory.”

    In my opinion, this means the quantum vacuum has a set of possibilities that it is free to actualize as long as those actualizations don’t violate a few conservation laws. I would call this “partial free will,” which is in contrast to “total free will,” where the quantum vacuum would be free to actualize any possibility. There is also the ever-present state where the quantum vacuum has “no free will.” The quantum vacuum must actualize possibilities. The quantum vacuum is not free to not actualize. The Totalitarian Principle compels the quantum vacuum to actualize possibilities. However, even though the quantum vacuum must actualize possibilities, not forbidden by a few conservation laws, the possibility it actualizes is not predetermined. The possibility the quantum vacuum actualizes is probabilistic, meaning there’s a chance the quantum vacuum could actualize one possibility or another. I would call this “partial probabilistic free will.”

    On a moment to moment basis, I believe each of us finds ourselves with the same type of “free will” as the quantum vacuum. Each moment we have a set of possibilities (thoughts, feelings, images, actions) that we are free to actualize as long as those actualizations don’t violate a few conservation laws. I would call this our “partial free will,” which is in contrast to “total free will,” where we would be free to actualize any possibility. There is also the ever-present state where we have “no free will.” We must actualize possibilities. We are not free to not actualize. Just like the quantum vacuum, the Totalitarian Principle compels us to actualize possibilities. However, even though we must actualize possibilities, not forbidden by a few conservation laws, the possibility (thought, feeling, image, action) we actualize is not predetermined. The possibility we actualize is probabilistic, meaning there’s a chance we could actualize one possibility or another. I would call this “partial probabilistic free will.” Consequently, I believe that we have partial probabilistic free will and that our partial probabilistic free will is based on the physics of quantum fields and the Totalitarian Principle.

  14. The question of Free Will and QM depends on which of the interpretations of QM one finds most compelling and whether that interpretation is compatible with a concept of ‘free will’. I have my favorite interpretation and it is sad that it is not getting more ‘air play’ because it deserves much more attention. That is the ‘Possibiliistic/Relativistic Transactional Interpretation’ of Ruth E Kastner. ( See: )

    I find it to be a compelling and powerful approach that has fundamental philosophical implications not only for free will but also for the connection between QM and panpsychism.

      • You bet it is. And Ruth is a tremendous person who has struggled as a woman in a field that is dominated by white men who have not given her approach a fair read. I happen to think she is on to something extremely important with her approach which differentiates between a relational realm of ‘possibility’ (ie. QuantumWorld in her books for the layperson published by World Scientific) which corresponds to David Bohm’s ‘Implicate Order’ and a realm of physical ‘actuality’ (ie. ManifestWorld) which we live in and which Nominalism tells us, quite falsely as it turns out, that this is our only reality. What you see is what you get–right? That is the by-line for Nominalism. And Charles Sanders Peirce told us a long time ago that inherent in Nominalism is a ‘deep threat’ which we now see playing out in our world to the detriment of the planet and everything on it. There is a scientific extension for physical science–it is called ‘Semiotics’, the science of Relationality. The science that operates out of a foundation laid by Iain McGilchrist’s ‘Master’ right hemisphere. We are stuck in the quicksand of Nominalism. Which is the science of the ‘Emissary’ left hemisphere which has assumed the role of the ‘Master’ much to the detriment of the planet, our glorious and abiding Mother. Who is now calling out desperately for our help and our attention and our compassion.

        As Peter Kingsley says in his book, ‘A Story Waiting to Pierce You’, we have forgotten the ‘original instructions’ of Western civilization that he traces back to a pact between Pythagorus and Abaris the Hyperborean, carrier of the Golden Arrow. As Kingsley points out in a very poignant way, we are doomed if we continue along the current track of Nominalism that sees no value in Relation, only in Substance. It de-personalizes and it puts the ‘Emissary’ in charge of the ‘Master’ creating a ‘topsy-turvy’ situation that is taking the planet down.

        We need a new story, a new narrative. The indigenous Elders are telling us that. Their prophecy is telling us that. We are in dire straits as they say.

        There is much more to be said about all of this but I will stop here…

  15. Pingback: Does Quantum Mechanics allow for Free Will? – Conscience and Consciousness - Nobodys word

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