Reggie Ugwu

After we’ve made a decision, to stay home rather than go to a dinner party, say, or to profess our love to someone, we ruminate over what we imagine as equally plausible alternative outcomes. Would we be happier if we had decided to go to the party? Would we regret not having shared how we feel?

But in what sense were those other futures available to us? Did we ever really have a choice? Or was what we perceived to be a decision actually predetermined, the result of a hidden conspiracy between our physical environment — the chance of rain, the temperature of the room — and the hard wiring of our brains?

Those questions, the subject of a centuries-old scientific debate about the possibility of free will, lay at the center of two high-profile television shows this season, “Westworld” (HBO) and “Devs” (FX on Hulu). In different ways, both series invoked the idea of “determinism,” which holds that our every thought, blink and utterance was ordained at the Big Bang and predicted by immutable laws of physics.

On “Devs,” a limited series created by Alex Garland, the writer and director of “Ex Machina,” a shamanic Silicon Valley founder named Forest (Nick Offerman) drops the truth bomb. “The life we lead, with all its apparent chaos, is actually a life on tram lines,” he says. Annoyingly to Forest, those tram lines are invisible. So he devises an astonishing workaround: an extraordinarily powerful quantum computer (art-directed to look like the real ones at Google and IBM) that can reveal the past and future of every particle in existence.

Season 3 of “Westworld,” which concluded on Sunday, also involves a clairvoyant supercomputer that allows its creator to play God. A French megalomaniac (Vincent Cassel) has built a system that can predict and manipulate the behavior of nearly everyone on earth. Despite their delusions of supremacy and monstrous ingenuity, the human characters, it turns out, aren’t any more autonomous than the androids they’ve been tormenting.

As in all good sci-fi, what makes these ideas unsettling is the ring of truth. But what does science really tell us about free will? Did I write these words of my own volition? Are you reading them according to yours? Or are our lives, as Forest says, hauntingly, just “something we watch unfold, like pictures on a screen?”

Seeking answers to those questions, and to other mind-bending provocations in each of the shows, I called the theoretical physicist Sean Carroll, a research professor at the California Institute of Technology and the author of several popular books, including “The Big Picture” and “Something Deeply Hidden.” He agreed to watch both series before we talked, ahead of the “Westworld” season finale. These are edited excerpts from our conversation.

What’s it like for you to watch things like this as someone who actually knows the science?

It’s a bittersweet experience. There’s a traditional thing that physicists do when they watch science fiction-y shows, which is roll their eyes at the implausibility. But I’ve tried my best to grow out of that. Instead, I try to appreciate how the storytellers use physics ideas to tell an interesting story. I think of these shows as more inspirational than educational. If they get people talking about big ideas and thinking them through deeply, then I think that’s all to the good.

Did you have a preference between the two shows?

With “Westworld,” I really enjoyed Season 1. Then I thought that it got a little complicated. This season, I’ve sort of lost the feeling of who I was supposed to be rooting for, so it’s a little less engaging.

With “Devs,” I was very impressed with how they were doing something very, very different. I thought it was a very well done show. It was slow and contemplative, but that’s a perfectly good change of pace from what we ordinarily see in action movies.

The computer in “Devs” is a quantum computer and the one in “Westworld” is described as an advanced A.I. Did you see an important difference there, in principle?

They portray them differently, but honestly it doesn’t matter even the slightest amount. There’s nothing about what the “Devs” computer was doing that was especially quantum — it just sounds cool. There’s no reason they couldn’t have just called it a classical computer. Likewise, the artificial intelligence aspect of the computer in “Westworld” is pretty optional. If what you’re trying to do is predict the future on the basis of the present, maybe an A.I. is useful to that, but it’s certainly not necessary. It’s just a matter of which buzzword you want to use. The computer in “Westworld,” I would say, is a little bit more realistic than the one in “Devs.” Nowhere near practical, but a little bit more believable.

A common thread between the two shows is the conflict between free will vs. determinism. Can you explain what determinism is?

Determinism is basically the idea that if you knew everything that was happening in the universe at one moment, then you would know, in principle, everything that was going to happen in the future, and everything that did happen in the past, with perfect accuracy. Pierre-Simone Laplace pointed this out in the 1800s using a thought experiment called Laplace’s Demon.

That sounds like what the computer in “Devs” is attempting to do. Could it exist?

No. And the most basic reason is that if you want to be Laplace’s Demon, you need to know the position and the velocity of every single particle in the universe, or at lest within several hundred light years. And no computer has any way of learning that, nor will they ever. Especially not if it’s a quantum computer, because by observing the quantum states of particles, you change them.

You couldn’t, as the show says, “extrapolate” from one particle, or group of particles, to deduce the state of all others?

Yeah, all that was just complete and utter nonsense. There’s nothing anywhere in physics that says anything like that. If I tell you, “Here’s a billiard ball, it just hit another billiard ball. Tell me where the other billiard ball is,” you couldn’t do that! There’s lots of different places the other billiard ball could be. If I told you where the billiard ball started and where it is now, then maybe you could figure out what happened in between. But that’s cheating — you wouldn’t be starting with just what’s in front of you.

Let’s talk about free will. Do we have it?

It’s complicated, and I apologize for that, but it’s worth getting right. The very first question we have to ask is: Are we human beings 100 percent governed by the laws of physics? Or do we, as conscious creatures, have some wiggle room that allows us to act in ways that are outside of the laws of physics? Almost all scientists will tell you that of course it’s the former. If you jump out of a window, the laws of physics say that you are going to hit the ground. You can use all of the free will you want, but it’s not going to stop you from hitting the ground. So why would you think that it works any differently when you go to decide what shirt you’re going to wear in the morning? It’s the same laws of physics. It’s just that one case is a more crude prediction and the other case is a more detailed prediction.

There’s another idea called libertarian free will, which says that human beings are a law unto themselves, not governed by the laws of physics. That’s an idea that is pretty strongly rejected by almost all scientists.

Did I make the choice to pick up the phone and call you?

Short answer: yes. Long answer: It depends on what you mean by “you” and “make the choice.” At one level, you’re a collection of atoms obeying the laws of physics. No choices are involved there. But at another level, you are a person who pretty obviously makes choices. The two levels are compatible, but speak very different languages. This is the “compatibilist” stance toward free will, which is held by a healthy majority of professional philosophers.

But isn’t that a rhetorical sleight of hand? If our choices are fully predetermined by physical processes outside of our control and beneath our consciousness, are they really choices? Or is that just a story we’re telling ourselves?

I think it’s the same as the chair you’re sitting on. Is it an illusion because it’s really just a bunch of atoms? Or is it really a chair? It’s both. You can talk about it as a set of atoms, but there’s nothing wrong with talking about it as a chair. In fact, you would be dopey to not talk about it as a chair, to insist that the only way to talk about it was as a set of atoms. That’s how nature is. It can be described using multiple different vocabularies at multiple different levels of precision.

At the level of precision where we’re talking about human beings and tables and chairs, you just can’t talk that way without talking about people making choices. There’s just no way to do it. You can hypothesize, “What if I had infinite powers and I knew where all the atoms were and I knew all the laws of physics.” Fine. But that’s not reality. If you’re reality based, then you have to talk about choices.

On both shows, the laws of physics are used to reframe the idea of morality. On “Devs,” Forest makes the argument that determinism is “absolution.” And there’s an idea in “Westworld” that humans are just “passengers”; forces beyond our control are behind the wheel. When you see people on the news, or even when you think about the people in your own life, does your belief in determinism affect the way you judge their behavior?

Not really, no. As long as you’re talking about a human-scale world. This idea that we are just puppets is clearly a mistake. It’s mixing up two different ways of talking about the world. There’s a way of talking about human beings going through their lives and making choices. There’s another way of talking about the laws of physics being deterministic and so forth. Those are two different ways — pick one.

Now, there are situations where we might learn that the choices that we thought people had are more circumscribed than we knew, either because of their biology or because of mental health issues, or what have you. By all means, take that into consideration. But that’s very human-scale stuff. If a person could not have acted otherwise, then you don’t hold them responsible in the same way. It’s not a matter of cutting edge science, it’s ancient law.

Another thread in both of these shows is the idea of a simulated world indistinguishable from ours. In what sense would a simulation be “real” for a person who was living in one?

Well they wouldn’t know any different. We could be living in a computer simulation now. If you believe, as I do, that things like our perceptions, our feelings, our thoughts, are all arising as emergent phenomena out of the interactions of physical stuff — atoms and forces and so forth — then you can absolutely imagine mimicking that to 100 percent accuracy in a computer simulation. It’s not practical to do it, now or maybe ever. But you can imagine it. And there’s no principled reason you would say those virtual beings inside your simulation are not feeling and experiencing the world in the same way that we are.

If I uploaded myself into a simulation, would it be me?

I think this gets into important issues very quickly. I would say that before you worry about whether you’re still you in the simulation, you should worry about whether you’re still the same person now that you were one minute ago. Clearly you’re similar in many ways; many of the atoms inside your body are the same. But not all of them — you’ve been breathing, and maybe some of your skin flaked off, etc. So there’s a relationship between you now and you one minute ago, but they’re not exactly the same person.

The same thing holds true if you’re trying to imagine uploading yourself into a computer. It wouldn’t be exactly you, but it could be related to you in some way. There’s not a binary choice between “me” or “not me.” We should be asking, rather: “In what way is this related to me or similar to me? Does it react to the world in the same way that I would?”

It’s like if you were to put yourself in a duplicator machine, like in “Calvin and Hobbes.” Which one is the real you? Well there’s no such thing as the real you. That’s not how things work. The idea that there’s this consciousness stuff that flows through you and therefore would have to be transferred over to the computer is just wrong.

So, if we find out on “Westworld” that William actually died at some point in the past and is now an android with William’s consciousness, would you say that it’s really him?

I would say that it’s a person that has a relationship to the previous William, in more or less the same way that the you of right now has a relationship to the you of five minutes ago.

What about organic life versus artificial life? There’s a refrain in “Westworld”: “If you can’t tell the difference, does it matter?” Do you think that it matters?

Well, the “hosts” on “Westworld” are kind of envisioned as robots — they’re obviously not like human beings. But you can imagine a world where we have artificial organisms that are humanlike and are made out of cells that adapt and repair themselves like we do. In that case, I don’t think there’s a hard, bright line between a living being and a nonliving being. It’s a continuum.

The Many Worlds theory of quantum mechanics, which says that there’s not one but many universes and that they’re constantly splitting off into new ones, plays a big role on “Devs.” You’re a proponent of the theory and wrote a book on it. What causes the universe to split?

Any time a small quantum system, like an electron, is in a superposition and comes into contact with the outside world, the universe branches. A superposition means that it could be in two different states — for example, spinning both clockwise and counterclockwise — at the same time.

How many universes have been created over the course of this phone call?

The sad news is we have no idea because our understanding of quantum mechanics isn’t quite what it should be. But it might be an infinite number. That sounds dramatic, but it might be a smooth, continuous process rather than a discrete sudden one. But it might not be! We just don’t know. We do know that it’s happening all the time — not once per minute, but many, many, many times per second.

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