Has Physics Ruled out Free Will (Patreon)

[This is a transcript with links to references.]

The future is determined by the past, except for random quantum jumps which no one can control. Causes have causes have causes, and they go back all the way to the big bang. Does that mean we have no free will? People often ask me that. I find the question stunningly uninteresting. Of course, we don’t have free will. Ok, then, how do we make decisions? Do we make decisions? Did the big bang make me do this video? That’s what we’ll talk about today.

I already made a video about free will a few years ago. But I’ve noticed recently that a lot of people think free will is relevant for addressing climate change. And because I don’t believe in free will I’ve suddenly become a problem. This is complete nonsense. But let’s start at the beginning.

And we begin of course with physics. Everything in the universe is made of 25 particles that, for all we currently know, are not themselves made of any smaller constituents. We collect them in what’s called the standard model of particle physics. That’s everything in the universe, except possibly dark matter, but that’s a different story.

Most of those particles are unstable and decay very quickly. How can it be that a particle which isn’t made of anything can decay? That’s a question I get so frequently, I made a video about that specifically.

For now, let’s stick with the particles that are stable. Those are the ones that we are made of, electrons, up and down quarks, and photons and gluons to hold them together. And good thing they’re stable because otherwise you’d be more radiant than a nuclear fuel rod. You’d also be dead very quickly.

Ok, so humans are one big collection of particles. What the particles do is described by the mathematics of the standard model. It’s a lot of maths, and you need that maths if you want to answer difficult questions like what’s going on in LHC collisions. For simple questions, like whether free will exists, we don’t need to know much about the maths. Relevant is just that, ultimately, what you and I do is also described by the standard model.

And yes, that means that we know the equations for human behaviour. We can write them down. In practice, that’s a completely useless statement, because we can’t solve the equations for all these 10 to the 30 or so particles that humans are made of. Not even the biggest supercomputer in the world could do that.

But we don’t need to solve the equations to draw conclusions from their properties. For the purposes of this video, the most relevant property of these equations is that they are deterministic, which means that if you know the properties and motions of the particles at one time, you can calculate what happens at any later time.

Ok, it isn’t quite as simple. Because this is quantum physics, so on top of this deterministic behaviour, there’s an occasional quantum jump which happens randomly whenever you make a measurement. Y’all know that I don’t believe this stuff with the quantum jumps. But today I’ll stick with the most generally accepted theory. So, we have particles that behave deterministically plus random jumps.

In quantum mechanics we use wave-functions to describe the particles, and this implies that there are some quantities, like position and momentum, whose values you can’t know precisely at the same time. But the wave-function still changes deterministically. If you want, you can include gravity, but that is just a deterministic theory. A non-quantum theory, or a “classical” theory as physicists say. So, gravity just adds some more determinism on top.

And that’s how the universe works, for all we currently know. It’s one big wave-function that contains all those particles. Its change in time is deterministic with the occasional random jump. The deterministic part is fixed by the past. The random jumps cannot be influenced by anything because that’s what it means for them to be random. And that’s it. Please don’t blame me for this. I swear it wasn’t my idea.

Physics is great, but it doesn’t tell you much about human anatomy, other than possibly that flapping your arms won’t make you fly. That’s because if you combine many particles, then things get very complicated very quickly. You get new, “emergent” behaviour as it’s often called.

You don’t even need to look at difficult things like human beings to see that. If you do as much as combine atoms to big chunks called metals you get new behaviour, like the ability to conduct electricity. Or being very shiny. Or being very painful if they fall on your foot.

Emergent properties don’t exist on the level of the constituents, they arise from the properties and interactions of the constitution. A single electron doesn’t have a conductivity. That just doesn’t make sense. Conductivity is a property that only makes sense for large collections of electrons.

It doesn’t make sense to talk about the conductivity of an electron for the same reason it doesn’t make sense to ask whether a single oxygen atom is a gas, or what’s the marital status of your small intestine. It’s what philosophers call a “category error”. It’d be trying to assign a property to a class to which it doesn’t belong. Emergent properties don’t make sense on the underlying levels. But that doesn’t mean they don’t exist. Chairs exist, alright, but they exist on the macroscopic level, and not on the level of elementary particles.

Curiously enough, our universe is organized so that the details of what happens at short distances become less important at large distances. This is why, if you want to understand planetary motion you don’t need to know the population of New York City. This is why, if you want to understand chemical reactions you don’t need to know the standard model of particle physics. And this is why, if you want to become a YouTuber, you don’t need to know anything.

Physicists call it the “decoupling of scales”, the mysterious but empirically well-confirmed fact that the details of what goes on small scales can be disregarded if you’re only interested in what happens on large scales. And this is why we have so many disciplines of science. Because each discipline of science has its own language about emergent properties that are adequate to its subject.

But that we get new, emergent, properties from the interactions of the constituents, doesn’t mean the equations that determine the behaviour of the constituents no longer apply. Emergent behaviour is a consequence of combining large numbers of particles with complicated interactions. It *follows from the underlying laws, it doesn’t make them go away.

Some philosophers have speculated that large systems could have emergent behaviours which *don’t follow from the laws of the constituents. This is sometimes called “strong emergence”. But there is no evidence this happens in the real world.

Though there are some mathematical examples. If you have an infinite number of constituents or an infinite number of properties of the constituents, or anything else being actually infinite, there are cases where it becomes impossible to calculate one or the other quantity of the entire system. A few examples for this have been constructed in the literature. Usually, the proof works by a map to the halting problems or similar examples of computational complexity. However, those are mathematical constructions that have no real-world counterpart because in the real world nothing is ever truly infinite.    

Ok, so emergent properties are an interesting consequence of the underlying laws, but we’re still governed by a mix of determinism and indeterminism. What does this mean for free will?

Free will is often described as the possibility that one could have done otherwise. But this description stopped being useful with quantum mechanics, because it’d mean that single particles also have free will.

If you take for example a photon, a single quantum of light, and you send it through a beam splitter, then there’s a 50 percent chance the photon goes left and 50 percent chance the photon goes right. If you measure the photon on the left you can say, well, it could have done otherwise. It could have gone right, right? Does that mean it has free will? Well, I’d say that’s not what normal people would call free will, though some physicists actually believe that photons are observers. One of the consequences of that is that they’ve concluded reality doesn’t exist. I talked about this in an earlier video.

This is also what happens in the “Free Will Theorem”. This theorem was mathematically proved by John Conway and Simon Kochen in 2006. It says that if humans have free will, then elementary particles also have free will. But the statement of the theorem is logically equivalent to the statement, “If particles do not have free will, then neither have humans.” I don’t know about you, but to me it seems reasonable to assume that particles do not have free will. And either way you put it, the free will theorem says nothing about the existence of free will in the first place.

So let’s return to the question of what we mean by free will. We have seen that the idea that you could have done otherwise or that your actions were not determined is not descriptive because of this random element from quantum mechanics. Contemporary philosophers have therefore tried to capture the essence of free will in the idea that human decisions are to a large extent independent from external factors, and instead dominantly driven by internal deliberation.

Different philosophers have put somewhat different spins on this story. But it always comes down to the idea that human decisions are difficult, if not impossible, to predict from external input and observations alone.

The philosopher Daniel Dennett for example captures the essence of free will in our “ability to see probable futures – futures that seem like they’re going to happen” and then the possibility to take steps that something else happens instead, like, for example an autonomous vehicle does. The philosopher Jennan Ismael has even written a book called “How Physics Makes Us Free”. She basically says that free will lies in the large degree of autonomy that our brain has from environmental factors as it operates.

Those are typical examples of what is called “compatibilism”, that’s the philosophy that free will is compatible with the laws of nature as they are, a mixture of determinism and indeterminism. Most contemporary philosophers are compatibilists. According to a 2020 survey, almost 60 percent. But it’s not like this is a new idea, well known philosophers like David Hume and John Stuart Mill were compatibilists.

The other big camp is that of libertarianism, whose supporters also believe in free will. Their philosophy comes in several variants. First, there are those who insist that the randomness of quantum mechanics makes place for free will. As I said, I don’t see how this makes sense. Then there are those who acknowledge that an element of indeterminism doesn’t entail free will, but who then throw out some established science to make place for miracles. Like for example the ability to change the past by your thoughts.

And then there are those who just insist that free will exists but it’s nonphysical. The latter is a well-trodden road. For example, Rene Descartes and Immanuel Kant were both in that camp. I’d say the idea is not wrong, but I never understood what the point is. Because if free will is not physical it doesn’t explain anything in the physical world, so why bother inventing it?

I am in neither of those camps. The science writer John Horgan once called me a “free will denier”. I think that’s a misunderstanding. It’s not that I’m denying people feel like they have free will. But I’m with libertarians in that I think free will is incompatible with determinism. I also think it’s incompatible with indeterminism. And since the real world is governed by a mixture of determinism and indeterminism, I arrive at the conclusion that free will doesn’t exist. It’s sometimes called “hard incompatibilism”.

The good thing about hard incompatibilism is that you don’t need to explain what free will is in any detail. You just need to say: whatever it is, it isn’t compatible with what we know about the laws of nature.

That said, I don’t have a problem with compatibilism. If you want to define whatever as free will, please go ahead, it’s just a definition after all. If your definition leads you to the conclusion that photons also have free will I’d find that a tad bit ridiculous but maybe that’s just me.

I should add that when neurologist discuss the question of free will they talk about something else entirely. They are concerned with the question whether we make decisions consciously or unconsciously. Interesting question, but not what I’m talking about today

I recently gave an interview and the guy said to me if free will doesn’t exist, why don’t I kill myself tomorrow because what’s the point of anything. This isn’t a joke, it actually happened. It wasn’t even the first time people said something like this to me. And I’m afraid it won’t be the last time. Which is why I’m here talking about free will again.

I’m not a psychologist. I’m a physicist. I don’t know what to say to people who have existential angst other than, please see a psychologist. I’m not a philosopher either. For what I am concerned, if free will doesn’t exist, it’s never existed, so what difference could it possibly make for your life.

I believe the problem is that many of us have grown up thinking our brain works in a particular way. Then we learn that this isn’t compatible with science, and we have a hard time readjusting how we think about ourselves.

The free will story suggests that the brain works like this. You use your neural circuits to consider different options, for example, what you could eat for lunch. You draw on your memory, and the associations you have for each possible option, and try to imagine how much you would enjoy it. Then you take this thing called “free will” and use it to pick one. The challenge is now to integrate the knowledge that the thing you call free will is just another part of this algorithm that runs in your neural circuits.

A good way I’ve found to make sense of this goes back to Wittgenstein. We can’t know the result of a calculation that our brain performs before we have completed the calculation. If we did, we wouldn’t have to do the calculation. This is why we have the impression that the decision is “free” until we’ve arrived at the conclusion. But the result ultimately follows from deterministic brain functions, with the occasional random element.

If that sounds weird, all it means is that our decisions follow from what we want. And I think that’s a good thing. I’d find it creepy if there was something else, call it free will or whatever, that would affect the decisions in my brain.

So that you don’t have free will doesn’t mean you don’t make decisions. Of course, you make decisions. You decided to watch this video, didn’t you? Good choice by the way.

Did the big bang made me do this video? No. That’s because all those structures in the universe, including this planet and life on it, were created by quantum fluctuations in the plasma in the early universe. Their details were not determined at the big bang, if there was a big bang. It’s also extremely likely that one or the other quantum event played a role for the world becoming just exactly as it is today.

Why does it matter? It matters because to come to good decisions we need to understand how our own brain works, and how society works overall. And the idea of free will suggests an inaccurate description of reality. It makes people believe they have more control over what goes on in their head than is really the case.

Fact is that our brains will process input whether we want that or not. Once it’s in, we can’t get it out. This is why trauma is so hard to cope with. This is why misinformation is so hard to combat. This is why what the FIFA called “three victorious hands around a soccer ball” will forever look like a facepalm once someone told you it does. You can’t “unsee” something.

And this is also why I take issue with upbeat climate change activists, who attack realists as “doomers” because they believe we just need the “will” to take action. The idea that “will” is all we need has led to utopian plans for staggering amounts of carbon capture, home insulation and renovation, upgrades of the electric grid, energy storage, and a hydrogen economy, all of which is somehow magically supposed to pop out of nowhere if we just have the “will”.  This belief in free will puts the blame on individuals when really the problem is the way that we’ve organized our societies.

I’d say it isn’t me who is a problem for action on climate change, it’s people who disregard the limits of human cognitive ability. I have a chapter about free will in my book “Existential Physics” where I also discuss the question of moral responsibility, so if you want to know more, go check this out.