Free will is dead, let’s bury it.

I wish people would stop insisting they have free will. It’s terribly annoying. Insisting that free will exists is bad science, like insisting that horoscopes tell you something about the future – it’s not compatible with our knowledge about nature.

According to our best present understanding of the fundamental laws of nature, everything that happens in our universe is due to only four different forces: gravity, electromagnetism, and the strong and weak nuclear force. These forces have been extremely well studied, and they don’t leave any room for free will.

There are only two types of fundamental laws that appear in contemporary theories. One type is deterministic, which means that the past entirely predicts the future. There is no free will in such a fundamental law because there is no freedom. The other type of law we know appears in quantum mechanics and has an indeterministic component which is random. This randomness cannot be influenced by anything, and in particular it cannot be influenced by you, whatever you think “you” are. There is no free will in such a fundamental law because there is no “will” – there is just some randomness sprinkled over the determinism.

In neither case do you have free will in any meaningful way.

These are the only two options, and all other elaborations on the matter are just verbose distractions. It doesn’t matter if you start talking about chaos (which is deterministic), top-down causation (which doesn’t exist), or insist that we don’t know how consciousness really works (true but irrelevant). It doesn’t change a thing about this very basic observation: there isn’t any known law of nature that lets you meaningfully speak of “free will”.

If you don’t want to believe that, I challenge you to write down any equation for any system that allows for something one could reasonably call free will. You will almost certainly fail. The only thing really you can do to hold on to free will is to wave hands, yell “magic”, and insist that there are systems which are exempt from the laws of nature. And these systems somehow have something to do with human brains.

The only known example for a law that is neither deterministic nor random comes from myself. But it’s a baroque construct meant as proof in principle, not a realistic model that I would know how to combine with the four fundamental interactions. As an aside: The paper was rejected by several journals. Not because anyone found anything wrong with it. No, the philosophy journals complained that it was too much physics, and the physics journals complained that it was too much philosophy. And you wonder why there isn’t much interaction between the two fields.

After plain denial, the somewhat more enlightened way to insist on free will is to redefine what it means. You might settle for example on speaking of free will as long as your actions cannot be predicted by anybody, possibly not even by yourself. Clearly, it is presently impossible to make such a prediction. It remains to be seen whether it will remain impossible, but right now it’s a reasonable hope. If that’s what you want to call free will, go ahead, but better not ask yourself what determined your actions.

A popular justification for this type of free will is insisting that on comparably large scales, like those between molecules responsible for chemical interactions in your brain, there are smaller components which may have a remaining influence. If you don’t keep track of these smaller components, the behavior of the larger components might not be predictable. You can then say “free will is emergent” because of “higher level indeterminism”. It’s like saying if I give you a robot and I don’t tell you what’s in the robot, then you can’t predict what the robot will do, consequently it must have free will. I haven’t managed to bring up sufficient amounts of intellectual dishonesty to buy this argument.

But really you don’t have to bother with the details of these arguments, you just have to keep in mind that “indeterminism” doesn’t mean “free will”. Indeterminism just means there’s some element of randomness, either because that’s fundamental or because you have willfully ignored information on short distances. But there is still either no “freedom” or no “will”. Just try it. Try to write down one equation that does it. Just try it.

I have written about this a few times before and according to the statistics these are some of the most-read pieces on my blog. Following these posts, I have also received a lot of emails by readers who seem seriously troubled by the claim that our best present knowledge about the laws of nature doesn’t allow for the existence of free will. To ease your existential worries, let me therefore spell out clearly what this means and doesn’t mean.

It doesn’t mean that you are not making decisions or are not making choices. Free will or not, you have to do the thinking to arrive at a conclusion, the answer to which you previously didn’t know. Absence of free will doesn’t mean either that you are somehow forced to do something you didn’t want to do. There isn’t anything external imposing on you. You are whatever makes the decisions. Besides this, if you don’t have free will you’ve never had it, and if this hasn’t bothered you before, why start worrying now?

This conclusion that free will doesn’t exist is so obvious that I can’t help but wonder why it isn’t widely accepted. The reason, I am afraid, is not scientific but political. Denying free will is considered politically incorrect because of a wide-spread myth that free will skepticism erodes the foundation of human civilization.

For example, a 2014 article in Scientific American addressed the question “What Happens To A Society That Does not Believe in Free Will?” The piece is written by Azim F. Shariff, a Professor for Psychology, and Kathleen D. Vohs, a Professor of Excellence in Marketing (whatever that might mean).

In their essay, the authors argue that free will skepticism is dangerous: “[W]e see signs that a lack of belief in free will may end up tearing social organization apart,” they write. “[S]kepticism about free will erodes ethical behavior,” and “diminished belief in free will also seems to release urges to harm others.” And if that wasn’t scary enough already, they conclude that only the “belief in free will restrains people from engaging in the kind of wrongdoing that could unravel an ordered society.”

To begin with I find it highly problematic to suggest that the answers to some scientific questions should be taboo because they might be upsetting. They don’t explicitly say this, but the message the article send is pretty clear: If you do as much as suggest that free will doesn’t exist you are encouraging people to harm others. So please read on before you grab the axe.

The conclusion that the authors draw is highly flawed. These psychology studies always work the same. The study participants are engaged in some activity in which they receive information, either verbally or in writing, that free will doesn’t exist or is at least limited. After this, their likeliness to conduct “wrongdoing” is tested and compared to a control group. But the information the participants receive is highly misleading. It does not prime them to think they don’t have free will, it instead primes them to think that they are not responsible for their actions. Which is an entirely different thing.

Even if you don’t have free will, you are of course responsible for your actions because “you” – that mass of neurons – are making, possibly bad, decisions. If the outcome of your thinking is socially undesirable because it puts other people at risk, those other people will try to prevent you from more wrongdoing. They will either try to fix you or lock you up. In other words, you will be held responsible. Nothing of this has anything to do with free will. It’s merely a matter of finding a solution to a problem.

The only thing I conclude from these studies is that neither the scientists who conducted the research nor the study participants spent much time thinking about what the absence of free will really means. Yes, I’ve spent far too much time thinking about this.

The reason I am hitting on the free will issue is not that I want to collapse civilization, but that I am afraid the politically correct belief in free will hinders progress on the foundations of physics. Free will of the experimentalist is a relevant ingredient in the interpretation of quantum mechanics. Without free will, Bell’s theorem doesn’t hold, and all we have learned from it goes out the window.

This option of giving up free will in quantum mechanics goes under the name “superdeterminism” and is exceedingly unpopular. There seem to be but three people on the planet who work on this, ‘t Hooft, me, and a third person of whom I only learned from George Musser’s recent book (and whose name I’ve since forgotten). Chances are the three of us wouldn’t even agree on what we mean. It is highly probable we are missing something really important here, something that could very well be the basis of future technologies.

Who cares, you might think, buying into the collapse of the wave-function seems a small price to pay compared to the collapse of civilization. On that matter though, I side with Socrates “The unexamined life is not worth living.”

10 Misconceptions about Free Will

If somebody talks about a “question that science cannot answer” what they really mean is a question they don’t want an answer to. Science can indeed be very disrespectful to people’s beliefs. I accept the wish to believe rather than know, but I get pissed off if somebody wraps their wishful thinking as an actual argument.

“Do humans have free will?” is a question I care deeply about. It lies at the heart of how we understand ourselves and arrange our living together. It also plays a central role for the foundations of quantum mechanics. In my darker moods I am convinced we’re not making any progress in quantum gravity because physicists aren’t able to abandon their belief in free will. And from the foundations of quantum mechanics the roadblock goes all the way up to neuroscience and politics.

Yes, I just blamed the missing rational discussion about free will for most of mankind’s problems, including quantum gravity.

Suggesting the absence of free will is apparently still an upsetter in the 21st century. You’re not supposed say it because allegedly just saying it makes other people immoral. Do you feel it already? How the immorality creeps from my blogpost into your veins? Aren’t you afraid to read on?

There’s no need to worry. This angst stems from a misunderstanding of what it means not to have free will. In this blogpost I address the most common misunderstandings, but before that let me explain why, to our best present knowledge of the laws of nature, you do not have free will. So, first the facts.

Fact 1: Everything in the universe, including you and your brain, is composed of elementary particles. What these particles do is described by the fundamental laws of physics. Everything else follows from that, in principle.

It follows in principle, but it is arguably not very practical to describe, say, human anatomy in terms of quarks and electrons. Instead, scientists of other disciplines use larger constituents and try to describe their behavior. This practical usefulness of increasingly larger scales, variables, and constituents, and the approximate accuracy of that procedure, is called “emergence”. All of these properties however derive from the fundamental description – in principle. That’s what is called reductionism.

The idea that the emergent properties of large systems do not derive from the fundamental description is called “strong emergence”. Some people like to claim that just because a system (eg your brain) consists of many constituents it is somehow exempt from reductionism and something (free will) “strongly emerges”. But fact is, there exists no known example where this happens, and there exists no known theory – not even an untested one – for how strong emergence can work. It is entirely irrelevant if your large system has adjectives like open, chaotic, complex or self-aware. It’s still just a really large number of particles that obey the fundamental laws of nature. Presently, believing in strong emergence is on the same intellectual level as believing in an immortal soul or in ESP.

Fact 2: All known fundamental laws of nature are either deterministic or random. To our best present knowledge, the universe evolves in a mixture of both, but just exactly how that mixture looks like will not be relevant in the following.

Having said that, I need to explain just exactly what I mean by the absence of free will:

a) If your future decisions are determined by the past, you do not have free will.

b) If your future decisions are random, meaning nothing can influence them, you do not have free will.

c) If your decisions are any mixture of a) and b) you do not have free will either.

In the above, you can read “you” as “any subsystem of the universe”, the details don’t matter. It follows straight from Fact 1 and Fact 2 that according to the definition of the absence of free will in a), b), c) free will is incompatible with what we presently know about nature.

I acknowledge that there are other ways to define free will. Some people for example want to call a choice “free” if nobody else could have predicted it, but for what I am concerned this is just pseudo free will.

Right! I didn’t say anything about neurobiology, the consciousness or the subconsciousness or about people pushing buttons. I don’t have to. For free will to exist it is necessary that free will be allowed by the fundamental laws of physics. It is necessary, but not sufficient: If you could make free will compatible with the laws of physics, it might still be that neurobiology finds your brain can’t make use of that option. Physics cannot tell you that free will exists, but it can tell you that it doesn’t exist. And that’s what I just told you.

Note that I neither claim strong emergence does not exist, nor do I say that a fundamental law has to be a mixture of determinism and randomness. What I am saying is this: If you want to argue that free will exists because strong emergence works, or there is an escape from determinism or randomness, then I want to see an example for how this is supposed to work.

Then let me address the main misconceptions:

1. If you do not have free will you cannot or do not have to make decisions.
   
   Regardless of whether you have free will or not, your brain performs evaluations and produces results and that’s what it means to make a decision. You cannot not make decisions. Just because your thought process is deterministic doesn’t mean the process doesn’t have to be executed in real time. The same is true if it has a random component.
   
   This misconception stems from a split-personality perspective: People picture themselves as trying to make a decision but being hindered by some evil free-will-defying law of nature. That is nonsense of course. You are whatever brain process works with whatever input you receive. If you don’t have free will, you’ve never had free will and so far you’ve lived just fine. You can continue to think the same way you’ve always thought. You’ll do that anyway.
   
   
2. If you do not have free will you have no responsibility for your actions.
   
   This misconception also comes from the split-personality perspective. You are what makes the decisions (takes in information and processes it) and performs the actions (acts on the results). If your actions are problematic for other people, you are the source of the problem and they’ll take measures to solve that problem. It’s not like they have any choice… If the result of your brain processes makes other people’s lives difficult, it’s you who will be blamed, locked away, sent to psychotherapy or get kicked where it really hurts. It is entirely irrelevant that your faulty information processing was inscribed in the initial conditions of the universe, the relevant question is what your future will bring if others try to get rid of you. The word ‘responsibility’ is just a red herring because it’s both ill-defined and unnecessary.
   
   
3. People should not be told they don’t have free will because that would undermine the rules of morally just societies.
   
   This misconception goes back to the first two and is based the idea that if people don’t have free will they don’t have any reason to reflect on their actions and to consider other people’s wellbeing. This is wrong of course. Evolution has endowed us with the ability to estimate the future impact of our actions and natural selection preferred those who acted so that others were supportive of their needs, or at least not outright aggressive towards them. If people don’t have free will they still have to make decisions and they still will be blamed for making other peoples’ lives miserable.
   
   Occasionally somebody refers me to this study which allegedly shows that “Encouraging a Belief in Determinism Increases Cheating.” This study also encourages misconception 2, so the finding is hardly surprising. I would like to see this repeated with the added explanation that the test subjects are of course still making decisions, regardless of whether the outcome was predetermined or not, and of course it matters what that outcome is.
   
   
4. If you do not have free will your actions can be predicted.
   
   Even if your brain processes were predictable in principle it is highly questionable anybody could do this in practice. Besides, as I explained above, these processes might have a random component that is even in principle not predictable. It is presently not very well understood just exactly how relevant such a random component might be.
   
   
5. If you do not have free will the future is determined by the past.
   
   Same misconception that underlies 4. Randomness is for all we presently know a component of the fundamental laws. In this case the future is not determined by the past, but neither do you have free will because nothing can influence this randomness.
   
   
6. If we do not have free will we can derive human morals.
   
   I don’t know why people get so hung up on this. Morals and values are just thought patterns that humans use to make decisions. Their relevance stems from these thought patterns being shared by many in similar versions. If the fundamental laws of the universe are deterministic and if you were really good at computation, then you could in principle compute them. In practice nobody can do it.
   
   It is also not actually what people mean when they talk about ‘deriving morals’. What they actually mean is whether one can derive what humans “should do”. That however one can only do once a goal is defined – “should do” to achieve what? – and that just moves the question elsewere. Science can’t answer this question because it’s ill-defined. Science can’t tell what anybody should be doing because that’s a meaningless phrase. Science can, in the best case, just tell what they will be doing.
   
   More to the point is (as I explained in length in this earlier blogpost) that at any time there are questions that science cannot answer because the knowledge we have is insufficient. These are the questions we leave to political decision. All the “should do” questions are of this type.
   
   
7. Free will is impossible.
   
   Not necessarily. As I explained here (paper here) it is possible to conceive of laws of nature that are neither deterministic nor random and that can plausibly be said to allow for free will. Alas, we do not presently have any evidence whatsoever that this is realized in nature and neither is it known whether this is even compatible with the laws of nature that we know. Send me a big enough paycheck and give me some years and I’ll find out.
   
   
8. You need to be a neuroscientist to talk about free will.
   
   We associate free will with autonomous systems that make choices, with activation patterns in human brains, which is the realm of neurobiology. However, your brain as much as every other part of the universe obeys the fundamental laws of nature. That these fundamental laws allow for free will is a necessary condition for free will to exist, and these laws fall into the realm of physics.
   
   
9. You need to be a philosopher to be allowed to talk about free will.
   
   If you want to know how everybody and their dog throughout the history of mankind defined free will, you had better read several thousand years’ worth of discussion on the issue. But I don’t like to waste time on definitions and I don’t see the merit in listing all variants of free will that somebody sometime has come up with. I told you above very clearly what I mean with ‘absence of free will’ and that is the core of the problem in two paragraphs. If you want to name this other than “free will”, I don’t care, it’s still the core of the problem.
   
   
10. If we do not have free will we cannot do science.
    
    I added this misconception because this comes up every time I talk about superdeterminism in quantum mechanics. The basic reason we can do science is that our universe evolves so that we are able to extract regularities in that evolution. You need to be able to measure what happens to similar systems under similar conditions and find patterns in that. But just how these similar systems came about is entirely irrelevant. It does not matter, for example, whether the laboratory and all the detector settings were predetermined already at the beginning of the universe. All that matters is that there are similar systems, that detections can be done, and the results are processed by you (or some computer) to extract regularities.

Let me be very clear that I didn’t say free will doesn’t exist. I said it doesn’t exist according to our best present knowledge of how nature works. If you want to hang on to free will you better come up with a really good idea how to make that compatible with existing scientific knowledge. I want to see progress, I don’t just want to see smoke screens of “strong emergence” or “qualia” and other fantasies.

You don’t have free will, but don’t worry.

Today I want to talk about an issue that must have occurred to everyone who spent some time thinking about physics. Which is that the idea of free will is both incompatible with the laws of nature and entirely meaningless. I know that a lot of people just do not want to believe this. But I think you are here to hear what the science says. So, I will tell you what the science says. In this video I first explain why free will does not exist, indeed makes no sense, and then tell you why there are better things to worry about.


I want to say ahead that there is much discussion about free will in neurology, where the question is whether we subconsciously make decisions before we become consciously aware of having made one. I am not a neurologist, so this is not what I am concerned with here. I will be talking about free will as the idea that in this present moment, several futures are possible, and your “free will” plays a role for selecting which one of those possible futures becomes reality. This, I think, is how most of us intuitively think of free will because it agrees with our experience of how the world seems to works. It is not how some philosophers have defined free will, and I will get to this later. But first, let me tell you what’s wrong with this intuitive idea that we can somehow select among possible futures.

Last week, I explained what differential equations are, and that all laws of nature which we currently know work with those differential equations. These laws have the common property that if you have an initial condition at one moment in time, for example the exact details of the particles in your brain and all your brain’s inputs, then you can calculate what happens at any other moment in time from those initial conditions. This means in a nutshell that the whole story of the universe in every single detail was determined already at the big bang. We are just watching it play out.

These deterministic laws of nature apply to you and your brain because you are made of particles, and what happens with you is a consequence of what happens with those particles. A lot of people seem to think this is a philosophical position. They call it “materialism” or “reductionism” and think that giving it a name that ends on –ism is an excuse to not believe it. Well, of course you can insist to just not believe reductionism is correct. But this is denying scientific evidence. We do not guess, we know that brains are made of particles. And we do not guess, we know, that we can derive from the laws for the constituents what the whole object does. If you make a claim to the contrary, you are contradicting well-established science. I can’t prevent you from denying scientific evidence, but I can tell you that this way you will never understand how the universe really works.

So, the trouble with free will is that according to the laws of nature that we know describe humans on the fundamental level, the future is determined by the present. That the system – in this case, your brain – might be partly chaotic does not make a difference for this conclusion, because chaos is still deterministic. Chaos makes predictions difficult, but the future still follows from the initial condition.

What about quantum mechanics? In quantum mechanics some events are truly random and cannot be predicted. Does this mean that quantum mechanics is where you can find free will? Sorry, but no, this makes no sense. These random events in quantum mechanics are not influenced by you, regardless of exactly what you mean by “you”, because they are not influenced by anything. That’s the whole point of saying they are fundamentally random. Nothing determines their outcome. There is no “will” in this. Not yours and not anybody else’s.

Taken together we therefore have determinism with the occasional, random quantum jump, and no combination of these two types of laws allows for anything resembling this intuitive idea that we can somehow choose which possible future becomes real. The reason this idea of free will turns out to be incompatible with the laws of nature is that it never made sense in the first place. You see, that thing you call “free will” should in some sense allow you to choose what you want. But then it’s either determined by what you want, in which case it’s not free, or it’s not determined, in which case it’s not a will.

Now, some have tried to define free will by the “ability to have done otherwise”. But that’s just empty words. If you did one thing, there is no evidence you could have done something else because, well, you didn’t. Really there is always only your fantasy of having done otherwise.

In summary, the idea that we have a free will which gives us the possibility to select among different futures is both incompatible with the laws of nature and logically incoherent. I should add here that it’s not like I am saying something new. Look at the writing of any philosopher who understand physics, and they will acknowledge this.

But some philosophers insist they want to have something they can call free will, and have therefore tried to redefine it. For example, you may speak of free will if no one was in practice able to predict what you would do. This is certainly presently the case, that most human behavior is unpredictable, though I can predict that some people who didn’t actually watch this video will leave a comment saying they had no other choice than leaving their comment and think they are terribly original.

So, yeah, if you want you can redefine “free will” to mean “no one was able to predict your decision.” But of course your decision was still determined or random regardless of whether someone predicted it. Others have tried to argue that free will means some of your decisions are dominated by processes internal to your brain and not by external influences. But of course your decision was still determined or random, regardless of whether it was dominated by internal or external influences. I find it silly to speak of “free will” in these cases.

I also find it unenlightening to have an argument about the use of words. If you want to define free will in such a way that it is still consistent with the laws of nature, that is fine by me, though I will continue to complain that’s just verbal acrobatics. In any case, regardless of how you want to define the word, we still cannot select among several possible futures. This idea makes absolutely no sense if you know anything about physics.

What is really going on if you are making a decision is that your brain is running a calculation, and while it is doing that, you do not know what the outcome of the calculation will be. Because if you did, you wouldn’t have to do the calculation. So, the impression of free will comes from our self-awareness, that we think about what to do, combined with our inability to predict the result of that thinking before we’re done.

I feel like I must add here a word about the claim that human behavior is unpredictable because if someone told you that they predicted you’d do one thing, you could decide to do something else. This is a rubbish argument because it has nothing to do with human behavior, it comes from interfering with the system you are making predictions for. It is easy to see that this argument is nonsense because you can make the same claim about very simple computer codes.

Suppose you have a computer that evaluates whether an equation has a real-valued root. The answer is yes or no. You can predict the answer. But now you can change the algorithm so that if you input the correct answer, the code will output the exact opposite answer, ie “yes” if you predicted “no” and “no” if you predicted “yes”. As a consequence, your prediction will never be correct. Clearly, this has nothing to do with free will but with the fact that the system you make a prediction for gets input which the prediction didn’t account for. There’s nothing interesting going on in this argument.

Another objection that I’ve heard is that I should not say free will does not exist because that would erode people’s moral behavior. The concern is, you see, that if people knew free will does not exist, then they would think it doesn’t matter what they do. This is of course nonsense. If you act in ways that harm other people, then these other people will take steps to prevent that from happening again. This has nothing to do with free will. We are all just running software that is trying to optimize our well-being. If you caused harm, you are responsible, not because you had “free will” but because you embody the problem and locking you up will solve it.

There have been a few research studies that supposedly showed a relation between priming participants to not believe in free will and them behaving immorally. The problem with these studies, if you look at how they were set up, is that people were not primed to not believe in free will. They were primed to think fatalistically. In some cases, for example, they were being suggested that their genes determine their future, which, needless to say, is only partly correct, regardless of whether you believe in free will. And some more nuanced recent studies have actually shown the opposite. A 2017 study on free will and moral behavior concluded “we observed that disbelief in free will had a positive impact on the morality of decisions toward others”. Please check the information below the video for a reference.

So I hope I have convinced you that free will is nonsense, and that the idea deserves going into the rubbish bin. The reason this has not happened yet, I think, is that people find it difficult to think of themselves in any other way than making decisions drawing on this non-existent “free will.” So what can you do? You don’t need to do anything. Just because free will is an illusion does not mean you are not allowed to use it as a thinking aid. If you lived a happy life so far using your imagined free will, by all means, please keep on doing so.

If it causes you cognitive dissonance to acknowledge you believe in something that doesn’t exist, I suggest that you think of your life as a story which has not yet been told. You are equipped with a thinking apparatus that you use to collect information and act on what you have learned from this. The result of that thinking is determined, but you still have to do the thinking. That’s your task. That’s why you are here. I am curious to see what will come out of your thinking, and you should be curious about it too.

Why am I telling you this? Because I think that people who do not understand that free will is an illusion underestimate how much their decisions are influenced by the information they are exposed to. After watching this video, I hope, some of you will realize that to make the best of your thinking apparatus, you need to understand how it works, and pay more attention to cognitive biases and logical fallacies.

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You probably have no free will. But don’t worry about it.

Railroad tracks. Image source.

Anybody who believes in reductionism and that the standard model of particle physics is correct to excellent precision must come to the conclusion that free will is an illusion. Alas, denial of this conclusion is widely spread, documented in many attempts to redefine “free will” so that it can somehow be accommodated in our theories. I find it quite amusing to watch otherwise sensible physicists trying to wriggle out of the consequences of their own theories. We previously discussed Sean Carroll’s attempt, and now Carlo Rovelli has offered his thoughts on free will in the context of modern physics in a recent Edge essay.

Free will can only exist if there are different possible futures and you are able to influence which one becomes reality. This necessitates to begin with that there are different possible futures. In a deterministic theory, like all our classical theories, this just isn’t the case - there’s only one future, period. The realization that classically the future is fully determined by the presence goes back at least to Laplace and it’s still as true today as it was then.

Quantum mechanics in the standard interpretation has an indeterministic element that is a popular hiding place for free will. But quantum mechanical indeterminism is fundamentally random (as opposed to random by lack of knowledge). It doesn’t matter how you define “you” (in the simplest case, think of a subsystem of the universe), “you” won’t be able to influence the future because nothing can. Quantum indeterminism is not influenced by anything, and what kind of decision making is that?

Another popular hiding place for free will is chaos. Yes, many systems in nature are chaotic and possibly the human mind has chaotic elements to it. In chaotic systems, even smallest mistakes in knowledge about the present will lead to large errors in the future. These systems rapidly become unpredictable because in practice measurement always contains small mistakes and uncertainties. But in principle chaos is entirely deterministic. There’s still only one future. It’s just that chaotic behavior spoils predictability in practice.

That brings us to what seems to me like the most common free will mirage, the argument that it is difficult if not impossible to make predictions about human behavior. Free will, in this interpretation, is that nobody, possibly not even you yourself, can tell in advance what you will do. That sounds good but is intellectually deeply unsatisfactory.

To begin with, it isn’t at all clear that it’s impossible to predict human behavior, it’s just presently not possible. Since ten thousand years ago people couldn’t predict lunar eclipses, this would mean the moon must have had free will back then. And who or what makes the prediction anyway? If no human can predict your behavior, but a computer cluster of an advanced alien civilization could, would you have free will? Would it disappear if the computer is switched on?

And be that as it may, these distractions don’t change anything about the fact that “you” didn’t have any influence on what happens in the future whether or not somebody else knew what you’ll do. Your brain is still but a machine acting on input to produce output. The evaluation of different courses of action can plausibly be interpreted as “making a choice,” but there’s no freedom to the result. This internal computation that evaluates the results of actions might be impossible to predict indeed, but this is clearly an illusion of freedom.

To add another buzzword, it also doesn’t help to refer to free will as an “emergent property”. Free will almost certainly is an emergent property, unless you want to argue that elementary particles also have free will. But emergent properties of deterministic systems still behave deterministically. In principle, you could do without the “emergent” variables and use the fundamental ones, describing eg the human brain in terms of the standard model. It’s just not very practical. So appealing to emergence doesn’t help, it just adds a layer of confusion.

Rovelli in his essay now offers a new free will argument that is interesting.

First he argues that free will can be executed when external contraints on choice are absent. He doesn’t explain what he means with “external constraints” though and I’m left somewhat confused about this. Is for example, alcohol intoxication a constraint that’s “external” to your decision making unit? Is your DNA an external constraint? Is a past event that induced stress trauma an external constraint? Be that as it may, this part of Rovelli’s argument is a rephrasing of the idea that free will means it isn’t possible to predict what course of action a person will take from exclusively external observation. As we’ve seen above, this still doesn’t mean there are different future options for you to choose from, it just means prediction is difficult.

Then Rovelli alludes to the above mentioned idea that free will is “emergent”, but he does so with a new twist. He argues that “mental states” are macroscopic and can be realized by many different microscopic arrangements. If one just uses the information in the mental states - which is what you might experience as “yourself” - then the outcome of your decisions might not be fully determined. Indeed, that might be so. But it’s like saying if you describe a forest as a lot of trees and disregard the details, then you’ll fail to predict an impending pest infection. Which brings us to the question whether forests have free will. And once again, failure to predict by disregarding part of the degrees of freedom in the initial state doesn’t open any future options.

In summary, according to our best present theories of nature humans don’t have free will in the sense explained above, which in my opinion is the only sensible meaning of the phrase. Now you could dismiss this and claim there must be something about nature then that these theories don’t correctly describe and that’s where free will hides. But that’s like claiming god hides there. It might be possible to construct theories of nature that allow for free will, as I suggested here, but we presently have absolutely zero evidence that this is how nature works. For all we know, there just is no free will.

But don’t worry.

People are afraid of the absence of free will not because it’s an actual threat to well-being, but because it’s a thought alien to our self-perception. Most people experience the process of evaluating possible courses of action not as a computation, but as making a decision. This raises the fear that if they don’t have free will they can no longer make decisions. Of course that’s wrong.

To begin with, if there’s no free will, there has never been free will, and if you’ve had a pleasant and happy life so far there is really no reason why this should change. But besides this, you still make your decisions. In fact, you cannot not make decisions. Do you want to try?

And the often raised concern about moral hazard is plainly a red herring. There’s this idea that if people had no free will “they” could not be made responsible for their decisions. Scare quotes because this suggests there are two different parts of a person, one making a decision and the other one, blameless, not being able to affect that decision. People who commit crimes cause pain to other people, therefore we take actions to prevent and deter crime, for which we identify individuals who behave problematically and devise suitable reactions. But the problem is their behavior and that needs to be addressed regardless of whether “they” have a freedom in their decision.

I believe that instead of making life miserable accepting the absence of free will will improve our self-perception and with it mutual understanding and personal well-being. This acceptance lays a basis for curiosity about how the brain operates and what part of decision making is conscious. It raises awareness of the information that we receive and its effect on our thoughts and resulting actions. Accepting the absence of free will doesn’t change how you think, it changes how you think about how you think.

I hope that this made you think and wish you a nice weekend :o)

Predetermined Lunch and Moral Responsibility

The final session of the 2011 FQXi conference concluded with a brief survey. The question “Is a ‘perfect predictor’ of your choices possible?” was answered with “Yes” by 17 out of 40 respondents. The follow-up question “If there were, would it undermine human free will?” was answered with “Yes” by 18 out of 38 respondents.

I’m in the Yes-Yes camp, and I was surprised that doubting one’s own free will was so common among the conference participants. It is striking how unrepresentative this result is for the general population who likes to hold on to the belief that personal choices are undetermined and unpredictable. In a cross-cultural study with participants from the United States, Hong Kong, India and Colombia, Sarkassian et al found that more than two thirds of respondents (82% USA, 85% India, 65% Hong Cong, 77% Colombia) believe that our universe is indeterministic and human decisions are “not completely caused by the past”(exact wording used in the study).

One of the likely reasons many people believe in free will is that if fundamentally there is no such thing as free will, how come that most of us* have the feeling that we do make decisions?

Lacking a good theory of consciousness, it may be that rather than making decisions, the role of our consciousness is to simply provide aggregated information about what our brain and body was doing, is currently doing, and provide a crude extrapolation of this information into the future. As we grow up, we become better at predicting what will be happening next –in our surrounding as well as with our own body and mind – and may mistake our prediction of what we will be doing for an intent to do it, and our imperfection of making precise predictions creates the illusion that we had a choice. (I doubt I'm the first to have this thought. If you know a reference with similar spirit, please let me know.)

This would mean, if you slap your forehead now, rather than consciously deciding to do so and making the choice to perform this action (which we may call the “standard interpretation”) your neuronal network has arrived at the necessary state that immediately precedes this action and your consciousness notes that next thing that will likely happen is you’ll be slapping your forehead, which it interprets as your impulse to do so (we may call it the “self-extrapolation interpretation”). You are not entirely certain about this since you have learned that your subconscious on occasion makes twists that your consciousness fails to properly predict, thus the possibility remains you’ll not be slapping your forehead after all.

It has in fact been argued that the reason why most people reject determinism it is their inability to predict actions, first by Thomas Reid I am told, and later by Spinoza, not that I actually read either. So possibly theoretical physicists are more inclined to believe in determinism because making precise predictions is their day job ;-)

Sean Carroll recently argued that free will can have a peaceful coexistence with modern science on an emergent level, in an effective description of human beings. That only works though if in the process of arriving at that effective level you throw away information that was fundamentally there. I believe Sean is aware of that when he writes “But we don’t know [all the necessary information to predict human decisions], and we never will, and therefore who cares?”

Well, I'd say that if you make room for free will by neglecting in principle available information, then his notion of free will is an empty concept that, as I've learned from the comments to his blogpost, the philosopher Edward Fredkin more aptly named “pseudo free will.”

I'm only picking around on Sean's post because it's short enough for you to go and read it unlike hundreds of pages that some philosophers have spent to say essentially the same thing. In any case, it is interesting how some scientists desperately try to hold on to some notion of free will in the face of an uncaring universe. I believe one of the reasons is that rejecting free will sheds a light of doubt on ones' moral responsibility, and since I feel personally offended, some words on that.

Morals and Responsibility

Whether the universe evolves deterministically, or whether its time evolution has a random element, an individual, fundamentally, has no choice over his or her actions in either case. It is then difficult to hold somebody responsible for actions if they had no way to make a different choice. This and similar thoughts have spurred a number of studies that claim to have shown that priming people’s belief in a deterministic universe reduces their moral responsibility.

For example, a study by psychologists Kathleen Vohs and Jonathan Schooler (summary here) had half of the participants read a text passage arguing against the existence of free will. All participants then filled out a survey on their belief in free will and completed an arithmetic test in which they had an option to cheat, but were asked not to. It turned out that disbelief in free will was correlated with the amount of cheating. Also, in the previously mentioned study by Sarkassian et al, most participants held the opinion that in a deterministic universe people are not responsible for their actions.

However, the issue of moral responsibility is a red herring, for morals are human constructs whether or not we have free will . From the viewpoint of natural selection, the reason why most of us don’t go around cheating, stealing, or generally making others suffer is not that it’s illegal or immoral or both, but that our self-extrapolation correctly predicts we will be suffering in return. Not primarily because we may be thrown into jail but because our brains would keep returning to that moment of offense, imagining how other people suffered because of our wrongdoing, telling us that way that we did act against the interests of our species, and more generally reducing our overall fitness.

In fact, that our species still exists and seems to be doing reasonably well means that most of us do not take pleasure in letting others suffer. The reason we don’t perform “immoral” acts is that we can’t: We’re the product of a billion years of natural selection that has done well to sort out those who pose a risk to our future, and we've called the result “moral.” (I am far from saying one can derive morals.)

The less consequences an act has for ones’ own future and that of others the larger the variety in people’s behavior. (There are more people jaywalking than strangling talk show hosts in front of running cameras.) That we have laws enforcing rules is because there remain people among us whose brains are some sigma away from the average and our laws are one more channel of natural selection, keeping these people off the streets, trying to readjust their brain’s functionality, or at least generally making their lives difficult. David Eagleman recently made a very enlightened argument for a rethinking of our justice system in light of neurobiological evidence for our reduced capability to change our brain’s working.

In a world without free will, we should not ask if a person is worth blaming, but simply look for the dominant cause of the problem and take steps to solve it.

Similarly, instead of asking if who is morally responsible we should ask what incentives do people have. The problem with the above mentioned test for moral responsibility in a deterministic universe it that the consequences of the alleged “immoral” act of cheating are entirely negligible. Putting forward the plausible thesis that the illusion of free will is beneficial to our brain’s performance (or otherwise, why is it so universal?), the test subject’s cheating might have been simply a reassurance of their illusion. If one would replace the temptation to cheat on a test with a questionnaire for the participant’s likings in food and then offer snacks, chances are those who were suggested a deterministic universe would feel the urge to select a food they do not usually prefer. Better still, one may have told the test subjects that the better their brains in the deterministic universe are adapted to living a modern life in modern times, the less likely they will be to perform “immoral acts” that violate the (written or unwritten) rules and values of that society (whether that is true or not doesn't matter).

Predetermined Lunch: Not Free Either

That our decisions are determined does not mean that we do not have to make them, which is a common misunderstanding, nicely summarized by Sean Carroll’s anecdote

“John Searle has joked that people who deny free will, when ordering at a restaurant, should say ‘just bring me whatever the laws of nature have determined I will get.’”

The decision what you will eat may be predetermined, but your brain still has to crunch the numbers and spit out a result. One could equally well joke that your computer, rather than running the code you’ve written, returns it back to you with the remark that the result is predetermined and follows from your input. Which is arguably true, but still somebody or something has to actually perform the calculation. Though in a deterministic universe it is in principle possible, it is highly questionable that the cook will be able to make the prediction about your order in your place, even after asking Laplace’s demon for input.

In other words, even if you don't have a free will, to make a decision you still have to collect all the information you deem necessary and scan your memory and experience to build an opinion, or perform whatever other process you have come to think is a good way to make decisions, may that be rolling a dice or calling your mom. Whether or not you believe you have a freedom in making a decision doesn’t save you the energy needed to do it.

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The original version of this post had a poll included on the question "Do you believe in free will?" but the applet is no longer functional. The results were

• I believe human decisions are in principle predictable and there is no free will. 35.4% (45)
• I believe human decisions are in principle predictable, but still there can be free will. 28.3% (36)
• I believe human decisions are not predictable, neither in practice nor in principle, and we have free will. 27.6% (35)
• I believe something else that I'll explain in the comments. 8.7% (11)

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* The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, describes Depersonalization Disorder as follows: “The essential features of Depersonalization Disorder are persistent or recurrent episodes of depersonalization characterized by a feeling of detachment or estrangement from one's self. The individual may feel like an automaton or as if he or she is living in a dream or a movie. There may be a sensation of being an outside observer of one's mental processes, one's body, or parts of one's body.”

Thus, interestingly enough, not all of us share the feeling of being in charge of one's actions. That the failure to relate to oneself is filed under "disorder" seems to me to show that believing in free will is beneficial to the individual's functionality and well-being.

How to live without free will

Lego sculpture.
By Nathan Sawaya.
[Image Source]

It’s not easy, getting a PhD in physics. Not only must you learn a lot, but some of what you learn will shake your sense of self.

Physics deals with the most fundamental laws of nature, those from which everything else derives. These laws are, to our best current knowledge, differential equations. Given those equations and the configuration of a system at one particular time, you can calculate what happens at all other times.

That is for what the universe without quantum mechanics is concerned. Add quantum mechanics, and you introduce a random element into some events. Importantly, this randomness in quantum mechanics is irreducible. It is not due to lack of information. In quantum mechanics, some things that happen are just not determined, and nothing you or I or anyone can do will determine them.

Taken together, this means that the part of your future which is not already determined is due to random chance. It therefore makes no sense to say that humans have free will.

I think I here spell out only the obvious, and use a notion of free will that most people would agree on. You have free will if your decisions select one of several possible futures. But there is no place for such a selection in the laws of nature that we know, laws that we have confirmed to high accuracy. Instead, whatever is about to happen was already determined at the big bang – up to those random flukes that come from quantum mechanics.

Now, some people try to wiggle out of this conclusion by defining free will differently, for example by noting that no one can in practice predict your future behavior (at least not currently). One can do such redefinitions, of course, but this is merely verbal gymnastics. The future is still fixed up to occasional chance events.

Others try to interpret quantum randomness as a sign of free will, but this is in conflict with evidence. Quantum processes are not influenced by conscious thought. Chaos is deterministic, so it doesn’t help. Goedel’s incompleteness theorem, remarkable as it is, has no relevance for natural laws.

The most common form of denial that I encounter is to insist that reductionism must be wrong. But we have countless experiments that document humans are made of particles, and that these particles obey our equations. This means that also humans, as collections of those particles, obey these equations. If you try to make room for free will by claiming humans obey other equations (or maybe no equation at all), you are implicitly claiming that particle physics is wrong. And in this case, sorry, I cannot take you seriously.

These are the typical objections that I hear, and none of them makes much sense.

I have had this discussion many times. Many people find it hard to comprehend that I do not believe in free will. And any such debate will, inevitably, be accompanied by the joke that the outcome of the argument was determined already, haha, aren’t you so original.

I have come to the conclusion that a large fraction of people are cognitively unable to question the existence of free will, and there is no argument that can change their mind. Therefore, the purpose of this blogpost is not to convince those who are resistant to rational arguments. The purpose is to help those who understand the situation but have trouble making sense of it. Like I have had trouble. The following shifts in perspective may help you without the need to resort to denial:

1. You never had free will.

It’s not like your free will suddenly evaporated when you learned the Euler-Lagrange equations. Your brain still functions the same way as before. So keep on doing what you have been doing. To first approximation that will work fine: Free will is a stubbornly persistent illusion, just use it and don’t worry about it being an illusion.

2. Your story hasn’t yet been told.

Free will or not, you have a place in history. Whether yours will be a happy story or a sad story, whether your research will ignite technological progress or remain a side-note in obscure journals, whether you will be remembered or forgotten – we don’t yet know. Instead of thinking of yourself as selecting a possible future, try to understand your role, and remain curious about what’s to come.

3. Input matters.

You are here to gather information, process it, and come to decisions that may, or may not result in actions. Your actions, and the information you share, will then affect the decisions and actions of others. These decisions are determined by the structure of your brain and the information you obtain. Rather than despairing over the impossibility of changing either, decide to be more careful which information you seek out, analyze, and pass on. Instead of thinking about influencing the future, ask yourself what you have learned, eg, from reading this. You may not have free will, but you still make decisions. You cannot not make decisions. You may as well be smart about it.

4. Understand yourself.

No one presently knows exactly what consciousness is or what it is good for, but we know that parts of it are self-monitoring, attentional focus, and planning ahead. A lot of the processes in your brain are not conscious, presumably because that would be computationally inefficient. Unconscious processes, however, can affect your conscious decisions. If you want to make good decisions, you must understand not only the relevance of input, but also how your own brain works. Instead of thinking that your efforts are futile, identify your goals and the strategies you have for working towards them. You are monitoring the monitor, if you wish.

Does Superdeterminism save Quantum Mechanics? Or Does It Kill Free Will and Destroy Science?

[This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.]


Superdeterminism is a way to make sense of quantum mechanics. But some physicists and philosophers have argued that if one were to allow it, it would destroy science. Seriously. How does superdeterminism work, what is it good for, and why does it allegedly destroy science? That’s what we’ll talk about today.

First things first, what is superdeterminism? Above all, it’s a terrible nomenclature because it suggests something more deterministic than deterministic and how is that supposed to work? Well, that’s just not how it works. Superdeterminism is exactly as deterministic as plain old vanilla determinism. Think Newton’s laws. If you know the initial position and velocity of an arrow, you can calculate where it will land, at least in principle. That’s determinism: Everything that happens follows from what happened earlier. But in quantum mechanics we can only predict probabilities for measurement outcomes, rather than the measurement outcomes themselves. The outcomes are not determined, so quantum mechanics is indeterministic.

Superdeterminism returns us to determinism. According to superdeterminism, the reason we can’t predict the outcome of a quantum measurement is that we are missing information. This missing information is usually referred to as the “hidden variables”. I’ll tell you more about those later. But didn’t this guy what’s his name Bell prove that hidden variables are wrong?

No, he didn’t, though this is a very common misunderstanding, depressingly, even among physicists. Bell proved that a hidden variables theory which is (a) local and (b) fulfills an obscure assumption called “statistical independence” must obey an inequality, now called Bell’s inequality. We know experimentally that this inequality is violated. It follows that any local hidden variable theory which fits to our observations, has to violate statistical independence.

If statistical independence is violated, this means that what a quantum particle does depends on what you measure. And that’s how superdeterminism works: what a quantum particle does depends on what you measure. I’ll give you an example in a moment. But first let me tell you where the name superdeterminism comes from and why physicists get so upset if you mention it.

Bell didn’t like the conclusion which followed from his own mathematics. Like so many before and after him, Bell wanted to prove Einstein wrong. If you remember, Einstein had said that quantum mechanics can’t be complete because it has a spooky action at a distance. That’s why Einstein thought quantum mechanics is just an average description for a hidden variables theory. Bell in contrast wanted physicists to accept this spooky action. So he had to somehow convince them that this weird extra assumption, statistical independence, makes sense. In a 1983 BBC interview he said the following:

“There is a way to escape the inference of superluminal speeds and spooky action at a distance. But it involves absolute determinism in the universe, the complete absence of free will. Suppose the world is super-deterministic, with not just inanimate nature running on behind-the-scenes clockwork, but with our behavior, including our belief that we are free to choose to do one experiment rather than another, absolutely predetermined, including the “decision” by the experimenter to carry out one set of measurements rather than another, the difficulty disappears.”

This is where the word “superdeterminism” comes from. Bell called a violation of statistical independence “superdeterminism” and claimed that it would require giving up free will. He argued that there are only two options: either accept spooky action and keep free will which would mean that Bell was right, or reject spooky action but give up free will which would mean that Einstein was right. Bell won. Einstein lost.

Now you all know that I think free will is logically incoherent nonsense. But even if you don’t share my opinion, Bell’s argument just doesn’t work. Spooky action at a distance doesn’t make any difference for free will because the indeterministic processes in quantum mechanics are not influenced by anything, so they are not influenced by your “free will,” whatever that may be. And in any case, throwing out determinism just because you don’t like its consequences is really bad science.

Nevertheless, the mathematical assumption of “statistical independence” has since widely been called the “free will” assumption, or the “free choice” assumption. And physicists stopped questioning it to the point that today most of them don’t know that Bell’s theorem even requires this additional assumption.

This is not a joke. All the alleged strangeness of quantum mechanics has its origin in nomenclature. It was forced on us by physicists who called a mathematical statement the “free will assumption”, never mind that it’s got nothing to do with free will, and then argued that one must believe in it because one must believe in free will.

If you find this hard to believe, I can’t blame you, but let me read you a quote from a book by Nicolas Gisin, who is Professor for Physics in Geneva and works on quantum information theory.

“This hypothesis of superdeterminism hardly deserves mention and appears here only to illustrate the extent to which many physicists, even among specialists in quantum physics, are driven almost to despair by the true randomness and nonlocality of quantum physics. But for me, the situation is very clear: not only does free will exist, but it is a prerequisite for science, philosophy, and our very ability to think rationally in a meaningful way. Without free will, there could be no rational thought. As a consequence, it is quite simply impossible for science and philosophy to deny free will.”

Keep in mind that superdeterminism just means statistical independence is violated which has nothing to do with free will. However, even leaving that aside, fact is, the majority of philosophers either believe that free will is compatible with determinism, about 60% of them, or they agree with me that free will doesn’t exist anyway, about 10% of them.

But in case you’re still not convinced that physicists actually bought Bell’s free will argument, here is another quote from a book by Anton Zeilinger, one of the probably most famous physicists alive. Zeilinger doesn’t use the word superdeterminism in his book, but it is clear from the context that he is justifying the assumption of statistical independence. He writes:

“[W]e always implicitly assume the freedom of the experimentalist. This is the assumption of free will… This fundamental assumption is essential to doing science.”

So he too bought Bell’s claim that you have to pick between spooky action and free will. At this point you must be wondering just what this scary mathematical expression is that supposedly eradicates free will. I am about to reveal it, brace yourself. Here we go.

I assume you are shivering in fear of being robbed of your free will if one ever were to allow this. And not only would it rob you of free will, it would destroy science. Indeed, already in 1976, Shimony, Horne, and Clauser argued that doubting statistical independence must be verboten. They wrote: “skepticism of this sort will essentially dismiss all results of scientific experimentation”. And here is one final quote about superdeterminism from the philosopher Tim Maudlin: “besides being insane, [it] would undercut scientific method.”

As you can see, we have no shortage of men who have strong opinions about things they know very little about, but not like this is news. So now let me tell you how superdeterminism actually works, using the double slit experiment as an example.

In the double slit experiment, you send a coherent beam of light at a plate with two thin openings, that’s the double slit. On the screen behind the slit you then see an interference pattern. The interference isn’t in and by itself a quantum effect, you can do this with any type of wave, water waves or sound waves for example.

The quantum effects only become apparent when you let a single quantum of light go through the slits at a time. Each of those particles makes a dot on the screen. But the dots build up… to an interference pattern. What this tells you is that even single particles act like waves. This is why we describe them with wave-functions usually denoted psi. From the wave-function we can calculate the probability of measuring the particle in a particular place, but we can’t calculate the actual place.

Here’s the weird bit. If you measure which slit the particles go through, the interference pattern vanishes. Why? Well, remember that the wave-function – even that of a single particle – describes probabilities for measurement outcomes. In this case the wave-function would first tell you the particle goes through the left and right slit with 50% probability each. But once you measure the particle you know 100% where it is.

So when you measure at which slit the particle is you have to “update” the wave-function. And after that, there is nothing coming from the other slit to interfere with. You’ve destroyed the interference pattern by finding out what the wave did. This update of the wave-function is sometimes also called the collapse or the reduction of the wave-function. Different words, same thing.

The collapse of the wave-function doesn’t make sense as a physical process because it happens instantaneously, and that violates the speed of light limit. Somehow the part of the wave-function at the one slit needs to know that a measurement happened at the other slit. That’s Einstein’s “spooky action at a distance.”

Physicists commonly deal with this spooky action by denying that wave-function collapse is a physical process. Instead, they argue it’s just an update of information. But information about… what? In quantum mechanics there isn’t any further information beyond the wave-function. Interpreting the collapse as an information update really only makes sense in a hidden variables theory. In that case, a measurement tells you more about the possible values of the hidden variables.

Think about the hidden variables as labels for the possible paths that the particle could take. Say the labels 1 2 3 go to the left slit and the labels 4 5 6 go to the right slit and the labels 7 to 12 go through both. The particle really has only one of those hidden variables, but we don’t know which. Then, if we measure the particle at the left slit, that simply tells us that the hidden variable was in the 1 2 3 batch, if we measure it right, it was in the 4 5 6 batch, if we measure it on the screen, it was in the 7 - 12 batch. No mystery, no instantaneous collapse, no non-locality. But it means that the particle’s path depends on what measurement will take place. Because the particles must have known already when they got on the way whether to pick one of the two slits, or go through both. This is just what observations tell us.

And that’s what superdeterminism is. It takes our observations seriously. What the quantum particle does depends on what measurement will take place. Now you may say uhm drawing lines on YouTube isn’t proper science and I would agree. If you’d rather see equations, you’re most welcome to look at my papers instead.

Let us then connect this with what Bell and Zeilinger were talking about. Here is again the condition that statistical independence is violated. The lambda here stands for the hidden variables, and rho is the probability distribution of the hidden variables. This distribution tells you how likely it is that the quantum particle will do any one particular thing. In Bell’s theorem, a and b are the measurement settings of two different detectors at the time of measurement. And this bar here means you’re looking at a conditional probability, so that’s the probability for lambda given a particular combination of settings. When statistical independence is violated, this means that the probability for a quantum particle to do a particular thing depends on the detector settings at the time of measurement.

Since this is a point that people often get confused about, let me stress that it doesn’t matter what the setting is at any earlier or later time. This never appears in Bell’s theorem. You only need to know what’s the measurement that actually happens. It also doesn’t matter how one chooses the detector settings, that never makes any appearance either. And contrary to what Bell and Zeilinger argued, this relation does not restrict the freedom of the experimentalist. Why would it? The experimentalist can measure whatever they like, it’s just that what the particle does depend on what they measure.

And of course this won’t affect the scientific method. What these people were worrying about is that random control trials would be impossible if choosing a control group could depend on what you later measure.

Suppose you randomly assign people into two groups to test whether a vaccine is efficient. People in one group get the vaccine, people in the other group a placebo. The group assignment is the “hidden variable.” If someone falls ill, you do a series of tests to find out what they have, so that’s the measurement. If you think that what happens to people depends on what measurement you will do on them, then you can’t draw conclusions about the efficiency of the vaccine. Alrighty. But you know what, people aren’t quantum particles. And believing that superdeterminism plays a role for vaccine trials is like believing Schrödinger’s cat is really dead and alive.

The correlation between the detector settings and the behavior of a quantum particle which is the hallmark of superdeterminism only occurs when quantum mechanics would predict a non-local collapse of the wave-function. Remember that’s what we need superdeterminism for: that there is no spooky action at a distance. But once you have measured the quantum state, that’s the end of those violations of statistical independence.

I should probably add that a “measurement” in quantum mechanics doesn’t actually require a measurement device. What we call a measurement in quantum mechanics is really any sufficiently strong or frequent interaction with an environment. That’s why we don’t see dead and alive cats. Because there’s always some environment, like air, or the cosmic microwave background. And that’s also why we don’t see superdeterministic correlations in people.

Okay, so I hope I’ve convinced you that superdeterminism doesn’t limit anyone’s free will and doesn’t kill science, now let’s see what it’s good for.

Once you understand what’s going on with the double slit, all the other quantum effects that are allegedly mysterious or strange also make sense. Take for example a delayed choice experiment. In such an experiment, it’s only after the particle started its path that you decide whether to measure which slit it went through. And that gives the same result as the usual double slit experiment.

Well, that’s entirely unsurprising. If you considered measuring something but eventually didn’t, that’s just irrelevant. The only relevant thing is what you actually measure. The path of the particle has to be consistent with that. Or take the bomb experiment that I talked about earlier. Totally unsurprising, the photon’s path just depends on what you measure. Or the quantum eraser. Of course the path of the particle depends on what you measure. That’s exactly what superdeterminism tells you!

So, in my eyes, all those experiments have been screaming us into the face for half a century that what a quantum particle does depends on the measurement setting, and that’s superdeterminism. The good thing about superdeterminism is that since it’s local it can easily be combined with general relativity, so it can help us find a theory of quantum gravity.

Let me finally talk about something less abstract, namely how one can test it. You can’t test superdeterminism by measuring violations of Bell’s inequality because it doesn’t fulfil the assumptions of Bell’s theorem, so doesn’t have to obey the inequality. But superdeterminism generically predicts that measurement outcomes in quantum mechanics are actually determined, and not random.

Now, any theory that solves the measurement problem has to be non-linear, so the reason we haven’t noticed superdeterminism is almost certainly that all our measurements so far have been well in the chaotic regime. In that case trying to make a prediction for a measurement outcome is like trying to make a weather forecast for next year. The best you can do is calculate average values. That’s what quantum mechanics gives us.

But if you want to find out whether measurement outcomes are actually determined, you have to get out of the chaotic regime. This means looking at small systems at low temperatures and measurements in a short sequence, ideally on the same particle. Those measurements are currently just not being done. However, there is a huge amount of progress in quantum technologies at the moment, especially in combination with AI which is really good for finding new patterns. And this makes me think that at some point it’ll just become obvious that measurement outcomes are actually much more predictable than quantum mechanics says. Indeed, maybe someone already has the data, they just haven’t analyzed it the right way.

I know it’s somewhat boring coming from a German but I think Einstein was right about quantum mechanics. Call me crazy if you want but to me it’s obvious that superdeterminism is the correct explanation for our observations. I just hope I’ll live long enough to see that all those men who said otherwise will be really embarrassed.

Limits of Reductionism

Almost forgot to mention I made it 3rd prize in the 2018 FQXi essay contest “What is fundamental?”

The new essay continues my thoughts about whether free will is or isn’t compatible with what we know about the laws of nature. For many years I was convinced that the only way to make free will compatible with physics is to adopt a meaningless definition of free will. The current status is that I cannot exclude it’s compatible.

The conflict between physics and free will is that to our best current knowledge everything in the universe is made of a few dozen particles (take or give some more for dark matter) and we know the laws that determine those particles’ behavior. They all work the same way: If you know the state of the universe at one time, you can use the laws to calculate the state of the universe at all other times. This implies that what you do tomorrow is already encoded in the state of the universe today. There is, hence, nothing free about your behavior.

Of course nobody knows the state of the universe at any one time. Also, quantum mechanics makes the situation somewhat more difficult in that it adds randomness. This randomness would prevent you from actually making a prediction for exactly what happens tomorrow even if you knew the state of the universe at one moment in time. With quantum mechanics, you can merely make probabilistic statements. But just because your actions have a random factor doesn’t mean you have free will. Atoms randomly decay and no one would call that free will. (Well, no one in their right mind anyway, but I’ll postpone my rant about panpsychic pseudoscience to some other time.)

People also often quote chaos to insist that free will is a thing, but please note that chaos is predictable in principle, it’s just not predictable in practice because it makes a system’s behavior highly dependent on the exact values of initial conditions. The initial conditions, however, still determine the behavior. So, neither quantum mechanics nor chaos bring back free will into the laws of nature.

Now, there are a lot of people who want you to accept watered-down versions of free will, eg that you have free will because no one can in practice predict your behavior, or because no one can tell what’s going on in your brain, and so on. But I think this is just verbal gymnastics. If you accept that the current theories of particle physics are correct, free will doesn’t exist in a meaningful way.

That is as long as you believe – as almost all physicists do – that the laws that dictate the behavior of large objects follow from the laws that dictate the behavior of the object’s constituents. That’s what reductionism tells us, and let me emphasize that reductionism is not a philosophy, it’s an empirically well-established fact. It describes what we observe. There are no known exceptions to it.

And we have methods to derive the laws of large objects from the laws for small objects. In this case, then, we know that predictive laws for human behavior exist, it’s just that in practice we can’t compute them. It is the formalism of effective field theories that tells us just what is the relation between the behavior of large objects and their interactions to the behavior of smaller objects and their interactions.

There are a few examples in the literature where people have tried to find systems for which the behavior on large scales cannot be computed from the behavior at small scales. But these examples use unrealistic systems with an infinite number of constituents and I don’t find them convincing cases against reductionism.

It occurred to me some years ago, however, that there is a much simpler example for how reductionism can fail. It can fail simply because the extrapolation from the theory at short distances to the one at long distances is not possible without inputting further information. This can happen if the scale-dependence of a constant has a singularity, and that’s something which we cannot presently exclude.

With singularity I here do not mean a divergence, ie that something becomes infinitely large. Such situations are unphysical and not cases I would consider plausible for realistic systems. But functions can have singularities without anything becoming infinite: A singularity is merely a point beyond which a function cannot be continued.

I do not currently know of any example for which this actually happens. But I also don’t know a way to exclude it.

Now consider you want to derive the theory for the large objects (think humans) from the theory for the small objects (think elementary particles) but in your derivation you find that one of the functions has a singularity at some scale in between. This means you need new initial values past the singularity. It’s a clean example for a failure of reductionism, and it implies that the laws for large objects indeed might not follow from the laws for small objects.

It will take more than this to convince me that free will isn’t an illusion, but this example for the failure of reductionism gives you an excuse to continue believing in free will.

Full essay with references here.

The Free Will Function

Last year's FQXi conference was a memorable event for me. Not only because it doesn't happen all that often that my conversation partners abandon their arguments to hurry away and find some more of these pills against motion sickness. But also because I was reassured that I am not the only physicist with an interest in questions that might become relevant only so far into the future that the time spent on them rests precariously on the edge between philosophy and insanity.

Scott Aaronson (who blogs at Shtetl-Optimized) went ahead and gave a talk about free will (summarized by George Musser here), which in return encouraged me to write up my thoughts on the topic, though I've still hidden them in physics.hist-ph (which I previously didn't even know exists!):

The Free Will Function

So, here's the executive summary.

In my previous post on free will, I explained that I don't buy the explanation that in a deterministic universe, or one with a random element, free will exists as an emergent property. If you call something free will that emerges from the fundamentally deterministic or probabilistic laws that we know, then I can't prevent you from doing that, but there isn't anything free to your will anymore. If free will is as real as a baseball, then you have as much freedom in making decisions as a baseball has to change its trajectory in Newtonian mechanics, namely none.

You might seek comfort in the fact that it is quite plausible that nobody can predict what you are doing, but this isn't freedom, it's just that nobody is able to document your absence of freedom. If your "will" is a property of a system that emerges from some microscopic laws, its laws might be for all practical purposes unknown, but in principle they still exist. If time evolution is deterministic, any choice that you make now strictly followed from an earlier state of the universe. If time evolution has a probabilistic element, as in quantum mechanics, then choices that you make now must not necessarily follow from earlier times, but you didn't have any choice either because the non-deterministic ingredient was just random.

Needless to say, I have greatly simplified. Notably, I've omitted everything about consciousness and the human brain. Look, I'm a particle physicist, not a neurologist. The exact working of the brain and the question whether quantum mechanics is relevant for biological processes don't change anything about the actual root of the problem: There is no room for anything or anybody to make a decisions in the fundamental laws of Nature that we know.

One way out of this problem is to believe in what is known as "strong emergence." That would be if the laws of the macroscopic emergent systems (e.g. "you") do not follow from the microscopic laws. The only people I have met who managed to make sense of this idea are philosophers. There is presently no formal way to achieve such a behavior and there is no known example how this could work. (We discussed here a paper that made an attempt into this direction, but note that the assumption of an infinite rather than a large system is crucial for that to work.) But yes, finding an example for strong emergence would be a possibility. Just that I couldn't find one.

My paper is much simpler than that. In my paper I just pointed out that there exist time evolutions that are neither deterministic nor probabilistic, certainly not in practice but also not in principle. Functions that do that for you are just functions physicists don't normally deal with. The functions that we normally use are solutions to differential equations. They can be forward-evolved or they can't and that is exactly the problem. Yet, there are lots of functions which don't fall in this category. These are functions can can be forward evolved, yet you have no way to ever find out how. They are deterministic, yet you cannot determine them.

Take for example a function that spits out one digit of the number π every second, but you don't know when it started or when it will end. You can record as much output from that function as you want, you'll never be able to tell what number you get in the next second: π is a transcendental number; every string that you record, no matter how long, will keep reappearing. If you don't know that the number is π you won't even be able to find out what number the algorithm is producing.

The algorithm is well-defined and it spits out numbers in a non-random fashion that, if you'd know the algorithm, is perfectly determined. But even if somebody monitors all output for an arbitrarily long amount of time to an arbitrarily good precision, it remains impossible to predict what the next output will be. This has nothing to do with chaos, where it's the practical impossibility of measuring to arbitrary precision that spoils predictability: Chaos is still deterministic. The same initial conditions will always give the same result, you just won't be able to know them well enough to tell. Chaos too doesn't allow you to make a choice, it just prevents you from knowing.

But what if you'd make your decisions after a function like the one I described? Then your decisions would not be random, but they wouldn't be determined by the state of the universe at any earlier time either (nor at any later time for that matter). You need to have your function to complete the time evolution, which is why I call it the "Free Will Function."

This is far too vague an idea to be very plausible, but I think it is interesting enough to contemplate. If you would like to believe in free will, yet your physics training has so far prevented you from making sense of it, maybe this will work for you!

If you found this interesting, George Musser has storified the topic, so you can continue reading.

Will the social sciences ever become hard sciences?

The term “hard science” as opposed to “soft science” has no clear definition. But roughly speaking, the less the predictive power and the smaller the statistical significance, the softer the science. Physics, without doubt, is the hard core of the sciences, followed by the other natural sciences and the life sciences. The higher the complexity of the systems a research area is dealing with, the softer it tends to be. The social sciences are at the soft end of the spectrum.

To me the very purpose of research is making science increasingly harder. If you don’t want to improve on predictive power, what’s the point of science to begin with? The social sciences are soft mainly because data that quantifies the behavior of social, political, and economic systems is hard to come by: it’s huge amounts, difficult to obtain and even more difficult to handle. Historically, these research areas therefore worked with narratives relating plausible causal relations. Needless to say, as computing power skyrockets, increasingly larger data sets can be handled. So the social sciences are finally on the track to become useful. Or so you’d think if you’re a physicist.

But interestingly, there is a large opposition to this trend of hardening the social sciences, and this opposition is particularly pronounced towards physicists who take their knowledge to work on data about social systems. You can see this opposition in the comment section to every popular science article on the topic. “Social engineering!” they will yell accusingly.

It isn’t so surprising that social scientists themselves are unhappy because the boat of inadequate skills is sinking in the data sea and physics envy won’t keep it afloat. More interesting than the paddling social scientists is the public opposition to the idea that the behavior of social systems can be modeled, understood, and predicted. This opposition is an echo of the desperate belief in free will that ignores all evidence to the contrary. The desperation in both cases is based on unfounded fears, but unfortunately it results in a forward defense.

And so the world is full with people who argue that they must have free will because they believe they have free will, the ultimate confirmation bias. And when it comes to social systems they’ll snort at the physicists “People are not elementary particles”. That worries me, worries me more than their clinging to the belief in free will, because the only way we can solve the problems that mankind faces today – the global problems in highly connected and multi-layered political, social, economic and ecological networks – is to better understand and learn how to improve the systems that govern our lives.

That people are not elementary particles is not a particularly deep insight, but it collects several valid points of criticism:

1. People are too difficult. You can’t predict them.
   
   Humans are made of a many elementary particles and even though you don’t have to know the exact motion of every single one of these particles, a person still has an awful lot of degrees of freedom and needs to be described by a lot of parameters. That’s a complicated way of saying people can do more things than electrons, and it isn’t always clear exactly why they do what they do.
   
   That is correct of course, but this objection fails to take into account that not all possible courses of action are always relevant. If it was true that people have too many possible ways to act to gather any useful knowledge about their behavior our world would be entirely dysfunctional. Our societies work only because people are to a large degree predictable.
   
   If you go shopping you expect certain behaviors of other people. You expect them to be dressed, you expect them to walk forwards, you expect them to read labels and put things into a cart. There, I’ve made a prediction about human behavior! Yawn, you say, I could have told you that. Sure you could, because making predictions about other people’s behavior is pretty much what we do all day. Modeling social systems is just a scientific version of this.
   
   This objection that people are just too complicated is also weak because, as a matter of fact, humans can and have been modeled with quite simple systems. This is particularly effective in situations when intuitive reaction trumps conscious deliberation. Existing examples are traffic flows or the density of crowds when they have to pass through narrow passages.
   
   So, yes, people are difficult and they can do strange things, more things than any model can presently capture. But modeling a system is always an oversimplification. The only way to find out whether that simplification works is to actually test it with data.
   
   
2. People have free will. You cannot predict what they will do.
   
   To begin with it is highly questionable that people have free will. But leaving this aside for a moment, this objection confuses the predictability of individual behavior with the statistical trend of large numbers of people. Maybe you don’t feel like going to work tomorrow, but most people will go. Maybe you like to take walks in the pouring rain, but most people don’t. The existence of free will is in no conflict with discovering correlations between certain types of behavior or preferences in groups. It’s the same difference that doesn’t allow you to tell when your children will speak the first word or make the first step, but that almost certainly by the age of three they’ll have mastered it.
   
   
3. People can understand the models and this knowledge makes predictions useless.
   
   This objection always stuns me. If that was true, why then isn’t obesity cured by telling people it will remain a problem? Why are the highways still clogged at 5pm if I predict they will be clogged? Why will people drink more beer if it’s free even though they know it’s free to make them drink more? Because the fact that a prediction exists in most cases doesn’t constitute any good reason to change behavior. I can predict that you will almost certainly still be alive when you finish reading this blogpost because I know this prediction is exceedingly unlikely to make you want to prove it wrong.
   
   Yes, there are cases when people’s knowledge of a prediction changes their behavior – self-fulfilling prophecies are the best-known examples of this. But this is the exception rather than the rule. In an earlier blogpost, I referred to this as societal fixed points. These are configurations in which the backreaction of the model into the system does not change the prediction. The simplest example is a model whose predictions few people know or care about.
   
   
4. Effects don’t scale and don’t transfer.
   
   This objection is the most subtle one. It posits that the social sciences aren’t really sciences until you can do and reproduce the outcome of “experiments”, which may be designed or naturally occurring. The typical social experiment that lends itself to analysis will be in relatively small and well-controlled communities (say, testing the implementation of a new policy). But then you have to extrapolate from this how the results will be in larger and potentially very different communities. Increasing the size of the system might bring in entirely new effects that you didn’t even know of (doesn’t scale), and there are a lot of cultural variables that your experimental outcome might have depended on that you didn’t know of and thus cannot adjust for (doesn’t transfer). As a consequence, repeating the experiment elsewhere will not reproduce the outcome.
   
   Indeed, this is likely to happen and I think it is the major challenge in this type of research. For complex relations it will take a long time to identify the relevant environmental parameters and to learn how to account for their variation. The more parameters there are and the more relevant they are, the less the predictive value of a model will be. If there are too many parameters that have to be accounted for it basically means doing experiments is the only thing we can ever do. It seems plausible to me, even likely, that there are types of social behavior that fall into this category, and that will leave us with questions that we just cannot answer.
   
   However, whether or not a certain trend can or cannot be modeled we will only know by trying. We know that there are cases where it can be done. Geoffry West’s city theory I find a beautiful example where quite simple laws can be found in the midst of all these cultural and contextual differences.

In summary.

The social sciences will never be as “hard” as the natural sciences because there is much more variation among people than among particles and among cities than among molecules. But the social sciences have become harder already and there is no reason why this trend shouldn’t continue. I certainly hope it will continue because we need this knowledge to collectively solve the problems we have collectively created.