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  • Writer's pictureEdgar Chicurel H

The Opposite of Free Will

Updated: Jul 28, 2021

Can physics predict our actions? If free will does not exist how do our thoughts form?

Lately, it seems that many a well respected author likes to remind us how free will is simply an illusion. Brian Greene, the brilliant physicist says so. So does acclaimed historian and philosopher Yuval Harari. Neuroscientist and philosopher Sam Harris even wrote a book about it. There is no free will, our decisions are not made by free will, we are told. All our decisions are the outcome of the aggregate of the actions of particles we are made of following precisely the laws of physics. We can never do anything that is in conflict with what our particles are going to do, and they are just going to obey whatever the fundamental laws of physics tell them to do. Don't even worry about it, they tell us, just accept it and keep living the illusion. Move on to the next page, please.

But before you move on to the next page, let's look a little closer at this argument. Strictly speaking, if we knew the state of each particle that makes up our brain we could predict what the possible outcomes would be when faced with a decision: each particle would behave unerringly within the dictates of physics. Of course, we would also have to know the state of all the particles in our body, since what we feel throughout our body affects our brain, thoughts and consequently decision making. And if you consider it more carefully, if we are making a decision that has to do with input from the outside world, which is usually the case (unless we are thinking all to ourselves in a perfectly isolated room), we probably need to know about the state of particles that are in our immediate surroundings.

For example, suppose you are on your smart phone finishing up a call with a friend and about to sit down and watch TV, but you are not sure whether to watch a news channel, or, the next episode of an entertaining series. Imagine you are finishing the call and just as you are about to put the phone down an alert pops up on your smartphone about a news item that interests you; there is a new US Open tennis champ reads the alert text. You want to know more about that, so you decide on the news channel; the text alert has made you decide against watching the series, at least for now. But if you had finished the call a moment earlier, or if, as you put the phone away you caught sight of your neighbor waving from her door, you might miss the news alert and settle down to watch the series. So to adequately model exactly what your decision will be you need to also know the state of the particles involved which may have any relevance to your seeing (or not) the news alert. This would include the particles making up your cell phone, your neighbor and the friend you were talking to who may have decided to extend the call a few more seconds (thus allowing you to note the news item alert) or cut it short because, for example her teapot started whistling. Of course the timing of when the tennis game ended and when the news alert is posted is also a factor which must be weighed in. If the person (or algorithm) tasked with posting new items does so a few seconds too late, you watch your series, if they post it earlier, you watch the news. So in this example, your decision depends on the activity of particles in many places, including those making up your friend, your neighbor, the tennis players, the tennis court, rackets and balls, the poster of the news alert, perhaps even the whistling teapot and its contents as well.

To determine what decision will be made based on particles and the laws of physics, even a trivial one like whether or not you take a look at a news show or TV series will depend on many particles in many places at a time. And, of course after predicting one decision the following prediction even a second later will depend on the updated state of all particles involved. Clearly our prediction of human decision-making through particles and laws of physics is becoming more complicated by the minute.

Take a much simpler example, one that does not involve conscious beings at all, in order to explore how predictions are affected by tiny perturbations which seem to have no relevance to our calculations. The physicist Sir Michael Berry proposed and analyzed the case of predicting bounces of billiard balls using straightforward Newtonian mechanics. If you have a billiard table with some billiard balls, a perfectly smooth, frictionless setup, with a few onlookers standing around, and you make your shot with absolute precision, how many bounces can you accurately predict? The onlookers are extremely well behaved, they do not speak or move, they do not touch the table, they hold their breaths and the air in the room is perfectly still so as not to affect the balls movement even a tiny bit. The only outside force that could have any effect on the balls' movements would be gravity, which we cannot block, but the gravity exerted by the onlookers is exceedingly small, so it would seem that there would be no need to include the mass and positions of the onlookers in our calculations. Surprisingly, Berry figured that to accurately predict just 6 or 7 bounces of a billiard ball on a frictionless table would require knowing where any onlooker is standing to account for the gravitational pull they would contribute to the balls movement. Clearly, no billiard player could ever predict the outcome of his shot after 6 bounces! The forces are tiny, but even a tiny change causes a noticeable effect after a few bounces. In fact to predict 50 bounces you would need to take into account the gravitational pull from an electron on the other side of the universe, in effect you would need to know the position of each particle in the universe.

This argument does not prove that free will exists. But it is clear that our thoughts and decisions cannot be predicted, that is to say our wills may not be free but there is no conceivable way that anyone could ever accurately predict what we will decide to do based on the laws of physics. Or, to be more precise, you could predict permitted decisions made by a person (not definite ones, as quantum mechanics gives us probabilities of particle state outcomes at a given moment in time) if you knew the sate of every particle in the universe, and were able to do the calculations necessary to solve for all possible future states.

In other words, perhaps in theory we can predict what a person will do armed with the complete laws of physics as well as a complete knowledge of the present state of the universe. Realistically, however, not only is this an impossible task based on our current tools and abilities, it is not conceivable that we could ever be able to perform these calculations. Moreover, it may well be that calculating states of the universe would require computer power that would exceed the resources of the universe itself.

From a physics point of view our decisions are, in fact, unpredictable. In other words, our will may not be free, but no one (using scientific principles) can ever predict what we will do. This means that the argument against free will is based only on the notion that we are somehow slaves to our particle states and the laws of physics they unswervingly obey. Our will is not free. It is enslaved will. To put it succinctly, the argument is that the laws of physics imply enslaved will.

So if free will cannot exist in a universe with the laws of physics we are familiar with, where could it ever exist? Are there laws of physics that could co-exist with free will? Imagine a world where everyone could agree there IS free will, what would it be made of? Particles that do what they are told? Or just pure and simple conscious agents? Cognitive psychologist Donald Hoffman's reasoning that we are looking at this the wrong way, and the fundamental building blocks of the universe have free will is, perhaps, the alternative.

But aren't our thoughts driven by free will? Didn't Descartes figure that you could doubt everything, your understanding of the world, the physical objects around you, the reality you are immersed in, your very senses but there was one single certainty we have as conscious beings. We know we think. I think therefore I am. But if free will is an illusion, then thought is also an illusion, because the basis of thought lies precisely in making decisions.

If you are going to turn the page on accepting that free will does not exist, you will also have to accept that free thought does not exist. The particles in our brain obey the laws of physics. But this very reasonable sounding assertion seems to imply that we do not control what we think. Really? Have we actually discovered, through physics, that the process of discovery itself is an illusion?

I believe we need a definition of free will which does not compete or contradict the fact that the universe and the stuff it is made up of obey laws. Decision making and our thought process are fundamental aspects of our consciousness, and denying that they are free because we know there are laws that govern the behavior of particles seems suspect. The equations of physics can describe our world with great detail and consistency, but let's keep in mind that our thought process, which depends on free will, is what has made it possible for us to formulate these equations in the first place.


I discovered Michael Berry's billiard ball exercise reading a short story called Anxiety is the Dizziness of Freedom from the book Exhalation by Ted Chiang. Despite the story's uninviting title, it is a really good one. Link below to an explanation by Michael Berry of his intriguing areas of research, including chaos theory and the billiard balls example.


Michael Berry interview where he describes the billiard ball prediction problem (PDF)

Brian Greene on Free Will (YouTube snippet)

Yuval Harari on Big Data, Google, and the end of Free Will (FT article)

Donald Hoffman: The Mystery of Free Will (Lecture on YouTube)

Sam Harris on Free Will (Lecture on YouTube)

John Horgan in Scientific American: Will This Post Make Sam Harris Change His Mind About Free Will? (Cross Check blog post)

Michio Kaku on Free Will (YouTube snippet)

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9 comentários

29 de jul. de 2021

Hi Edgar, I enjoyed your podcast, despite having consumed a lot and even thought some on this topic. Thanks for the listen! (and to Marina for the recommendation!) About the billiard balls personally I'd have liked to know what the unpredictability derived from (e.g. microscopic irregularities of the balls and/or the cushions), partly supposing it would flesh out my assumption that you're talking about chaos. It's my impression people will suppose something unrealistic and/or woo to fill such a gap, to the extent it's left vacant. - Oliver

30 de jul. de 2021
Respondendo a

FYI, by consulting your transcript I think I figured out why I idealized-away the thing that makes the 6th or 7th bounce unpredictable. First of all, you didn't *expressly* retract or revise the following aspect of the billiards experiment as you introduced it to us: "The onlookers are extremely well behaved, they do not speak or move, they do not touch the table, they hold their breaths and the air in the room is perfectly still so as not to affect the balls movement even a tiny bit." Second, I arrived with an idea of chaos in mind, and tend to hear things over-literally. Per my sometimes literal way also of talking, chaotic things are like everything else **insensitive** to…


Marina Chicurel
Marina Chicurel
25 de jul. de 2021

Accessible, thought-provoking, and fresh—I love this! Unlike other discussions of free will I’ve read before, this one was both engrossing and easy to follow. I didn’t get hopelessly lost, nor did I feel bored or talked down to. And to top it all off, the concluding thoughts left me surprisingly satisfied.

Edgar Chicurel H
Edgar Chicurel H
25 de jul. de 2021
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