What is causal determinism? What are some of the ways that physics can permit free will? What does emergence have to do with all of this? I discuss these questions and more in today’s Ask a Spaceman!

Support the show: http://www.patreon.com/pmsutter

All episodes: http://www.AskASpaceman.com

Watch on YouTube: http://www.youtube.com/PaulMSutter

Read a book: https://www.pmsutter.com/books

Keep those questions about space, science, astronomy, astrophysics, physics, and cosmology coming to #AskASpaceman for COMPLETE KNOWLEDGE OF TIME AND SPACE!

Big thanks to my top Patreon supporters this month: Justin G, Chris L, Alberto M, Duncan M, Corey D, Michael P, Naila, Sam R, Joshua, Scott M, Rob H, Scott M, Louis M, John W, Alexis, Gilbert M, Rob W, Jessica M, Jules R, Jim L, David S, Scott R, Heather, Mike S, Pete H, Steve S, Lisa R, Kevin B, Aileen G, Steven W, Deb A, Michael J, Phillip L, Steven B, Mark R, Alan B, Craig B, Richard K, Stephen J, Joe R, David P, Justin, Tracy F, Ella F, Thomas K, James C, Syamkumar M, Homer V, Mark D, Bruce A, Tim Z, Linda C, The Tired Jedi, Bob C, Stephen A, James R, Robert O, Allen E, Michael S, Reinaldo A, Sheryl, David W, Chris, Michael S, Erlend A, James D, Larry D, Karl W, Den K, Edward K, Craig M, Scott K, Vivek D, Barbara C, Brad, Azra K, Steve R, Koen G, and Scott N!

Hosted by Paul M. Sutter.

 

EPISODE TRANSCRIPT (AUTO-GENERATED)

Here you are, listening to this show. You made a conscious, willful decision to download this episode, to put your earbuds in, to press play. At any moment, you can decide you've had enough. You can press stop, delete this episode, and never hear from me again. Nobody is stopping you. There's no grand force in the universe that is conspiring to compel you. You made a choice, one of thousands of choices you've made today. You have free will. You have the ability to influence events around you, the capability to affect your words and actions, and the responsibility to be your own moral agent. But hold on, isn't there this thing called physics? Like, isn't the whole point of physics to build a causal structure to the universe? If we were to zoom into your brain as you're making a choice, all we would see is sodium ions wiggling back and forth and some electrical signals passing here and there. That's all physics. And we have laws of physics that describe and predict how it all goes down. So does physics destroy free will? If it's all just forces and laws and actions and reactions going all the way down to a subatomic level, then is what we call free will just an illusion? We have no choice but to try to answer this question.

Get it? It's a free will joke. Listen, if there's no free will, then I'm not really responsible for the quality of my jokes, right? Anyway, check this out. There are some experiments that just make you stop. Make you reconsider everything you've ever known. The kind of experiment where you just need to step outside into the cold air with your favorite beer or favorite kind of cheese or perhaps both and just stare at nothing for a while. And for me, one of those experiments was conducted by Benjamin Libet in the 1980s. He wired people up and asked them to just randomly flick their wrists whenever they feel like it. Totally random, totally their choice. He was measuring something called the readiness potential, which is a buildup of electrical signals in the brain just before you start moving. It's like the brain gearing up for action before it sends the signal down the nerves to make the movement happen. This was all well known for a couple decades, and it was all fine and a little bit boring.

But Libet added a twist. He had his subjects watch a clock and to note the time on the clock when they first felt the conscious sensation to move. In other words, he asked them to keep track of when they decided to flick their wrists. Then he compared that to when the buildup of the readiness potential happened. And it was later. I'm not kidding. According to all these measurements, the participants decided to flick their wrist in the sense that they were consciously aware of their random choice one fifth of a second after the brain had already begun the process of flicking the wrist. Go step outside if you need to. I'll be right here when you get back. There is no settled answer to this experiment. It could be that free will is an illusion and we just think we're making choices when really our brains are following a pre-programmed script set down by the laws of physics. Or maybe the readiness potential is just that, a readiness that preps the brain to activate in the potential for movement, but doesn't necessarily always lead to movement.

Or maybe it's something more complex. There's no settled answer to the entire question of free will. We've kind of been debating it for, let me see here, yep, yep, pretty much all history and probably longer. Now, I'm a lot of things. Cosmologist, science communicator, devoted husband and parent, amateur cheese enthusiast. But I'm also not a lot of things. I'm not a neurologist. I'm not a psychologist. I'm not a philosopher. Although, side nitpick, PhD literally stands for philosophy doctor. All scientists are automatically philosophers, just a specialized branch of philosophy. So to clarify, I'm a specialist within that branch, not an expert at other branches of philosophy. What this means is that unlike, I don't know, supernova explosions or the mass of the neutrino, I can't give you an answer to this question. I guess I can't give you an answer to those other questions, but in a different way. And I suspect that I, as a physicist, can't ever give you an answer to that question. You should be really, really cautious when anybody says they do have an answer to the question of free will, especially if they start their answer with, I'm a physicist.

But what we can do is explore what physics has to say about the subject, which while not arriving at a full answer is still a lot. And then we can use what physics has to say about the subject to guide our own thoughts and opinions and arguments. And that's pretty fun. And the first thing that physics has to say is that the universe is causally deterministic. Causal determinism is a mouthful, but what it means is that physics works. Every effect has a cause. A leads to B leads to C leads to a star blowing up or some molecules folding into a protein. And that we have laws of physics to guide us from A to B to C to stars blowing up. Ever since Galileo started the program of applying mathematics to physics, and yes, I really need to do a Galileo series, and I think I've been saying that for a couple years now, but I really mean it. Feel free to ask. That will spur me on. We've become ever more sophisticated in our ability to, A, describe natural processes with clever theories, and B, use those clever theories to predict what the future will hold.

The greatest articulation of this concept comes to us from Pierre-Simon Laplace, the Newton of France, who was smart enough to survive both the French Revolution and the rise and the fall of Napoleon, and in the meantime contribute to almost every single area of science because that's just what Laplace does. Laplace asked us to imagine a super intelligent being. which today we call Laplace's demon because that sounds sick as hell. And this being could take a snapshot of the position and momentum of every single particle in the universe. And from there, the demon could apply Newton's laws of motion to predict every single act that would ever occur in the future. Here's a bit from his 1815 philosophical essay on probabilities. Of course, I'm translating into nonfiction. We may regard the present state of the universe as the effect of its past and the cause of its future. An intellect which at a certain moment would know all forces that set nature in motion and all positions of all items of which nature is composed, if this intellect were also vast enough to submit these data to analysis, it would embrace in a single formula the movements of the greatest bodies of the universe and those of the tiniest atom.

For such an intellect, nothing would be uncertain, and the future, just like the past, could be present before its eyes. So yeah, where's the free will? There ain't none, or even room for the divine when Laplace once presented his work. Mechanique Celeste to Napoleon, the emperor asked him why he never even mentioned its creator, that is, God. Laplace's response? Quote, I had no need of that hypothesis. Dang, dude, tell us how you really feel. All of physics rests on causal determinism. It's like how we do physics. It is physics. It's how we make predictions for experiments and determine what the universe was like in its past. If we didn't have causal determinism, well, life would be a lot more difficult. Yes, Laplace's demon doesn't actually exist. And no, we don't have all the laws of physics. yet. And even if we never did, even if we stopped all of physics research and said, pack it in, everybody, we're giving up, what matters is that Laplace's idea works in principle. As long as you can imagine such a superintelligence, then causal determinism is true, and free will doesn't exist.

But wait, didn't Laplace live over 200 years ago? Hasn't physics advanced since then? Why do we care what some long-dead French guy has to say about the subject? Fair questions. physics has advanced a lot. And there are three branches of physics that, well, they don't exactly restore free will, but they certainly put some cracks in the whole causal determinism thing. And they certainly add a lot of color to this discussion. The first of those branches is chaos theory. If I gave you a pendulum, then I can perfectly predict its motion for all of eternity. You tell me the starting angle, the length of the string, the strength of Earth's gravity. I'm done. I can write down a single formula that will tell you exactly where that pendulum will be at any point in the infinite future. Causal determinism for the wind. Well, what if I gave you a double pendulum? First off, you think that I'm not the most thoughtful gift giver, and if I'm gifting double pendulums, I should just give you a card stuffed full of cash, which is fair.

But anyway, a double pendulum is one pendulum attached to the end of another pendulum. Here's the wild thing about double pendulums. Causal determinism? Check. All forces of nature and possible interactions? Known. Math? Simple. Straightforward. Ability to predict the future? Absolutely gone. A double pendulum is chaotic. These are physical systems that go on to random and unpredictable places despite us knowing the initial state as well as we can. Because if there's any amount of uncertainty whatsoever, even microscopic uncertainty, then our ability to predict the pendulum's behavior far into the future totally falls apart. To be able to predict the future, I don't just need the laws of physics. I need to know the initial state. I need to know exactly at what angle the pendulums started at. With a regular pendulum, if I'm a little off in my measurement of its position, It's no big deal. That uncertainty, that little bit of fuzziness doesn't go anywhere or do anything. It doesn't affect my ability to make future predictions.

But a double pendulum, a chaotic system, if its actual starting position is different by even a super tiny amount like a femtometer from what I think its starting position is, then chaos comes roaring in. The uncertainties in a chaotic system amplify on themselves as time goes on. And what I see is that at first, the double pendulum is kind of sort of close to where I predict it should be. But before long, it gets wildly out of step. And before I know it, I have no idea of what's going on or how to keep track of it. Causal determinism is still there. There's no magic divine finger that's reaching down from the heavens to nudge around the pendulum when I'm not looking. It's all just Newton's laws of gravity and F equals MA and all the usual stuff. It's causal. It's deterministic. It's unpredictable. Chaotic systems are everywhere. It's one of the reasons that weather is so hard to predict. It's not just because it's complex with lots of forces and interactions and particles involved. It's because it's chaotic.

Even a tiny, tiny, tiny, tiny misjudgment or error in measurement spirals out of control to the point that long-term prediction becomes impossible. Now, chaos theory doesn't sway the free will argument one way or the other, but it does color it. Like I said, chaos theory tells us that in certain cases, we can never make fully accurate predictions. Even Laplace's superintelligence is going to fall short because it's impossible to know the exact, precise starting state of every particle in the universe down to infinite precision. So chaos theory doesn't destroy determinism. It just makes it more fun. So it could be that free will still exists, or it could mean that free will doesn't exist, but we'll still never be able to predict the actions that we'll take. Actions and choices like contributing to Patreon. That's patreon.com slash pmsutter, where you get to support this show and keep it going. I truly appreciate all of your contributions. whether it's your free will choice or the universe compelling you.

Doesn't matter. Patreon.com slash PM Sutter. All contributions are accepted. And listen, I need to add a caveat before we keep going. I know I'm tying the question of free will to the question of determinism. I'm linking them together, which isn't necessarily the right thing to do. Because check this out. Because if you say, hey, determinism doesn't exist. And there can be effects without causes. then you can also say that we're not responsible for our actions because we have no will over them. Our choice to choose A or B is itself a cause that leads to an effect. It is in its own way a form of determinism. If you say determinism is out the window, there are things that happen with no cause, then you say, well, then my choices don't matter. I'm not influencing my environment. It's just random stuff happening. with no agency or input of our own. So in a way, you might need determinism to make free will happen because that's the only way we can be responsible for the choices we make. But there are, of course, philosophical arguments around that.

Like I said, we've had a lot of practice for the past few thousand years, and I'm not a philosopher. So I'm going to keep focusing on determinism because that's where physics has the most to say. And quantum mechanics has a lot to say about determinism. So let's say you set up an experiment to measure a quantum property of subatomic particles. Like, I don't know, spin. All fundamental particles have spin. And even though they're not actually tiny little spinning balls, we still pretend they are because the quantum world is weird. And we don't have a lot of experience with it. So we tend to reach for the nearest analogy we can first. And then we just kind of, it just kind of sticks, even though it doesn't make much sense. But then again, nothing really makes sense about quantum mechanics. Slow, exasperated sigh. Here's the thing. You run a quantum experiment, you don't get to know the answer ahead of time. It's all random, all probabilities, all wave function, this and born rule that. Oh, and the Heisenberg uncertainty principle, you know, the one that says we can never know precisely both the position and momentum of a subatomic particle.

Well, there goes any hopes of circumventing chaos theory by finding cheat codes to give you perfectly precise measurements. The Heisenberg uncertainty principle guarantees you never will. So that's nice. So can we find the origins of free will in quantum uncertainty? Kinda yes, kinda no, depending on how you want to take this. For one, quantum mechanics is still a theory of physics, which means it's still based on causal determinism. We just need to be careful about what we're determining. In quantum mechanics, effects still have causes. Event A still leads to event B. Nothing happens for no reason or out of nowhere. There are still laws of physics that govern the evolution of systems and allow us to predict what will happen in the future. But what quantum mechanics messes up is our ability to precisely predict what will happen in the future. We can instead only assign probabilities to various outcomes. You go to measure a quantum spin of a subatomic particle, you get a 50-50 shot of either getting spin up or spin down.

It won't be spin sideways or spin double, and it won't be 1% spin up and 99% spin down. We can make a prediction. You're going to get either spin up or spin down, and you have an equal chance of getting either of those two possibilities. We can't say which one you're guaranteed to get, but we can assign the probabilities and make calculations. We can still predict the future. We can still rest assured that causes lead to effects and the normal ordering of the flow of time makes sense and all that. We just have to insert a little bit of quantum fuzziness when we're talking about quantum systems. And then there's the whole correspondence principle. Quantum mechanics doesn't exist in a vacuum. It's part of a wider universe of the universe. We use quantum rules to understand quantum systems, which are almost always subatomic systems. We don't use quantum rules to describe literally everything else happening in the cosmos. If I throw an electron at you, quantum mechanics. If I throw a baseball at you, normal mechanics.

There must be a correspondence between these two realms, and that correspondence is governed by the correspondence principle, hence the name. It basically says that, yes, you can use quantum mechanics for quantum systems, but once you get a lot of particles together to make a macroscopic object, you're going to have to switch over to regular, not quantum at all physics. And this isn't just some fun idea. It's baked into quantum theory. When we first started encountering quantum systems, we had no idea what to use to guide our thinking in deciding what laws and rules and mathematics to apply and what not to apply. The correspondence principle helps us. If you want to make a quantum theory, then you better make sure that it recovers normal physics when you get to normal systems. But when and how this changeover from quantum to normal physics takes place is a bit of an unknown. So if the inner workings of our brains, especially the generation of decisions and the origin of free will, lays firmly in the quantum realm, then there may be some aspect of free will that we can never predict.

But since we strongly believe that the correspondence principle is true, and we have no reason to doubt it so far, and brains are obviously macroscopic systems, you can hold them in your hand if you work hard enough, it could be that quantum mechanics has absolutely nothing to say about free will at all, and this is just a red quantum herring. I do have to mention that there may be a way to get rid of all the quantum probabilities. That's through a concept called super determinism. If causal determinism wasn't enough for you, now we have super determinism. And the way this works is we usually think of quantum experiments from two sides. There's the quantum side involving the subatomic particles that do whatever the heck they want. And then there's us, the observers, the experimenters, the measurement makers who are not quantum objects at all and have things like free will. And we're here running our experiment on the quantum system. The quantum system is isolated and doing its quantum thing while us non-quantum things are doing the measurements.

The extremely short version of superdeterminism, I'm willing to do a whole episode on this if you want, is that we're all quantum systems, all entangled and interconnected with each other. And instead of random events, the entire quantum state of the universe evolved from a highly specific set of initial conditions to lead to a precise experimental predetermined outcome. In other words, you can get rid of the randomness of quantum experiments if you find a way for the universe to have no other choice but to lead to that result. Super determinism is not super well regarded because it opens up a lot of nasty, unanswered questions like how in the world did the entire universe's initial state be so perfectly finely tuned to give me this result and even our very existence instead of just a jumbled morass of incoherence. Also, it kind of destroys all the science because we don't learn anything about the universe by running experiments because all the outcomes are all predetermined, even at a quantum level.

But it also destroys free will at a quantum level, which is nice if that's the kind of thing you're going for. But then you're going to have to, you've got a lot explaining to do there, buddy. But like I said, happy to do a full episode on it if you want. But in this episode, we're not going for one thing or another. I'm not trying out here to destroy free will or support it. We're here to explore ideas. That's the fun part anyway. And there's one more aspect of physics that takes part in the free will discussion. And that's the concept of emergence. We have all these really fun and cool theories of physics, right? We have electromagnetism. We have quantum field theory. We have the Navier-Stokes equation. They're all really good and really powerful, and they tell us how very particular systems will evolve with time. They tell us the history of the universe, our weekend weather outlook, or what kinds of weird subatomic particles will come out when we smash stuff together really hard. But there's more to life and life in the universe than these laws.

And just because you can write down a law that describes one phenomena in one domain, it doesn't mean that you can automatically predict how other, larger, more complex systems will behave. Sometimes you can, for sure. Sometimes you can, like temperature. A single particle doesn't have a temperature. It has a position and a velocity. You ask a, hey, particle, what's your temperature? I said, what the heck are you talking about? I have position and velocity. That's what I got. What's this thing called temperature? I don't even know what you're talking about. But if you get a zillions of particles together, all of a sudden you get a new property of the whole system. the temperature of a box of particles. Temperature emerges from the individual motions of the particles, even though each individual particle has no idea what the heck you're talking about when you bring up the subject of temperature. And what's really cool about thermodynamics is that we actually have a way of connecting the microscopic properties of particles with the emergent macroscopic behavior.

And that's through a machine called statistical mechanics, which is beyond amazing and sadly not the subject of today's episode. But statistical mechanics is an exception, not a rule. Let me take a sappy extreme. Emotions. We all know that emotions have a physiological component. There are chemical and hormonal and physical changes that happen inside your body and your brain when you experience sadness or joy. Technically, if we boil everything down, it's all just a bunch of subatomic particles whizzing around. And we have a powerful theory of describing how subatomic particles behave. That's quantum field theory. So it should be true in a deterministic universe that you can start with quantum field theory and do enough work to eventually describe all the stuff happening in your brain and body when you get sad. Except we don't. And even worse, we can't. Emotions are an emergent property of the human body-brain system. There is no theory of physics that can describe the appearance of emotions based on fundamental principles.

There is no... And I mean it. I mean it. I'm not just saying hypothetical because it's really complicated. I'm saying you cannot... go from quantum field theory to emotions. Quantum theory has its domain of subatomic particles. But once you get a whole bunch of subatomic particles together to make a macroscopic system, new behaviors emerge that are not products of the fundamental theory. There is no quantum field theory that can describe what is happening in your brain and body when you get sick. even if we knew all the physics there was to know in the entire cosmos, and we ourselves became Laplace's demons, then we still couldn't use those fundamental physics to make predictions because emergence breaks the connection between fundamental microscopic behaviors and macroscopic manifestations. And it's in this language of emergence that there might be a way to preserve free will in a deterministic universe. Most philosophers, align with some shade of thought called compatibilism, which states that free will as we understand it, which is the freedom to make choices that are not caused or forced, with causal determinism.

I mean, let's say I give you a choice. Do you want a slice of, let me see here, I've got French Mimolette or, I don't know, a lovely Italian Scamorza? Either of those choices is compatible with all known laws of physics. Once you make the choice, the universe sets itself in motion. All else follows. Once you decide to eat the cheese, you just eat it. There's nothing weird there. The only thing that we're worried about is the choice itself. So maybe, big maybe here, there is some law of physics that we have not yet discovered that permits free will even in a deterministic universe. And the only reason that free will appears mysterious to us is that we have not yet advanced enough in our understanding of physics to make that kind of connection. One of my favorite books of all time is Gödel, Escher, Bach by Douglas Hofstadter, a philosopher. In the book, he uses examples from music and art and mathematics to show how simple, meaningless elements, when repeated in certain ways, can give rise to exceptionally complex, meaningful systems.

He proposes this as a way to understand consciousness and free will and choices, that there are rules that the universe obeys that can give rise to things like free will, where you can have your metaphysical cake and eat it too. That's generally my approach, but I'm not going to sit here and tell you what to think. Maybe physicists don't like the compatibilism option all that much because it makes us look sort of ignorant. They say, oh yeah, free will looks mysterious because you're not done doing physics yet, which I don't know, maybe there's a point there. Personally, I lean towards compatibilism because the nature of emergence, it's a very compelling angle to me. The way it colors this argument to say, yeah, we can write down fundamental physics, but that doesn't guarantee that we can use it to describe nature. And all sorts of surprising things happen in complex systems that we cannot predict from fundamental theories. On the other hand, there is so much we have yet to learn about how nature works.

And while determinism has served us well for many centuries, there should be no expectation that the way we currently understand it will be useful in the future. And maybe there's something special about free will that we'll never be able to capture with any of our understanding of physics. And that's okay. Or maybe free will doesn't exist after all, and all of this is just a blind alley and the universe really is deterministic. We don't know. We just have to keep our minds open to the choices the universe offers us. And yeah, that was another free will. Thank you to Darnell O, Francisco P, and Mike M for the questions that led to today's episode. Keep those questions coming. AskASpaceman at gmail.com or the website AskASpaceman.com. Love the questions, the lifeblood of this show. Please keep the reviews coming in on your favorite podcasting platform that really bumps the show's visibility. And of course, If you are able and willing, patreon.com slash pmsutter is how you can financially contribute to keeping this show going.

I'd like to thank my top Patreon contributors this month. They're Justin G., Chris L., Berto M., Duncan M., Corey D., Michael P., Nyla, Sam R., Joshua, Scott M., Rob H., Scott M., Lewis M., John W., Alexis, Gilbert M., Rob W., Jessica M., Jules R., Jim L., David S., Scott R., Heather, Mike S., Pete H., Steve S., Lisa R., Kevin B., Eileen G., Steven W, Deb A, Michael J, Philip L, and Steven B. That's patreon.com slash pmsutter. And I will see you next time for more complete knowledge of time and space. Thank you.

Comment