Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas - 25 | David Chalmers on Consciousness, the Hard Problem, and Living in a Simulation

Episode Date: December 3, 2018

The "Easy Problems" of consciousness have to do with how the brain takes in information, thinks about it, and turns it into action. The "Hard Problem," on the other hand, is the task of explaining our individual, subjective, first-person experiences of the world. What is it like to be me, rather than someone else? Everyone agrees that the Easy Problems are hard; some people think the Hard Problem is almost impossible, while others think it's pretty easy. Today's guest, David Chalmers, is arguably the leading philosopher of consciousness working today, and the one who coined the phrase "the Hard Problem," as well as proposing the philosophical zombie thought experiment. Recently he has been taking seriously the notion of panpsychism. We talk about these knotty issues (about which we deeply disagree), but also spend some time on the possibility that we live in a computer simulation. Would simulated lives be "real"? (There we agree -- yes they would.) David Chalmers got his Ph.D. from Indiana University working under Douglas Hoftstadter. He is currently University Professor of Philosophy and Neural Science at New York University and co-director of the Center for Mind, Brain, and Consciousness. He is a fellow of the Australian Academy of Humanities, the Academy of Social Sciences in Australia, and the American Academy of Arts and Sciences. Among his books are The Conscious Mind: In Search of a Fundamental Theory, The Character of Consciousness, and Constructing the World. He and David Bourget founded the PhilPapers project. Web site NYU Faculty page Wikipedia page PhilPapers page Amazon author page NYU Center for Mind, Brain, and Consciousness TED talk: How do you explain consciousness?

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If you're a QuickBooks customer looking to grow your business without the growing pains, you need the Intuit ERP. Upgrade to Intuit Enterprise Suite in a matter of hours. It's the AI native ERP from the makers of QuickBooks. Learn more at Intuit.com slash ERP. Hello everyone. Welcome to the Mindscape podcast. I'm your host, Sean Carroll. If any of you have read The Big Picture, my most recent book, you know that one of the things we have to think about, if we're naturalists, trying to come to terms with the world of our experience.

is the phenomenon of consciousness. Actually, most of you probably know that, even if you haven't read that book. It's a pretty well-known fact. The question, of course, is what is demanded of us by the fact of consciousness? Can we simply hope to explain consciousness using the same tools we explain other things with, atoms and particles moving according to the laws of physics, according to the standard model and the core theory, or do we need something else somehow that helps us explain what consciousness is and how it came about? So I'm someone who thinks we don't need anything else.

I think it's just understanding the motion and interactions of physical stuff from which consciousness emerges as a higher level phenomenon. Our guest today is David Chalmers, who is probably the most well-known and respectable representative of the other side, the people who think that you need something beyond just the laws of physics as we currently know them to account for consciousness. David is the philosopher who coined it the term the hard problem of consciousness. The idea being that the easy problems are, you know, how you look at things and why you react in certain ways, how you do math problems in your head. The hard problem being our personal experience, what it is like to be you or me rather than somebody else, the first person's subjective experience. That's the hard problem and someone like me thinks, oh yeah, we'll get there. It's just a matter of words and understanding and philosophy.

someone like David thinks we need a real change in our underlying way of looking at the world. So he describes himself as a naturalist, someone who believes in just the natural world, no supernatural world, not a dualist who thinks it's a disembodied mind or anything like that, but he's not a physicalist. He thinks that the natural world has not only natural properties, not only physical properties, but mental properties as well. So I would characterize him as convinced of the problem, but he's not wedded to any particular answer. David Jalmers is a philosopher who everyone respects, even if they don't agree with him. He's a delight to talk to because he is very open-minded about considering different things. Like I said, he's convinced of this

problem, but when it comes to solving the problem, he will propose solutions, but he won't take them too dogmatically. He will change his mind when good arguments comes along. So he's a great person to talk to about this very, very important problem for naturalists when they try to confront how to understand what it means to be a human being and where consciousness comes from. Also, David has developed a recent interest in the simulation hypothesis, the idea that maybe we could all be living in a simulation running on a computer owned by a very, very advanced civilization in a completely different reality. So we'll talk about the hard problem of consciousness. We'll talk about various philosophical issues. And, you know, I won't pin him down on anything. I'm not trying to argue with him. My point here is not to convince David Chalmers in real time that he's wrong, but rather to let you the listeners hear what his perspective is on these issues. And then, then hear what my perspective is on these issues and decide for yourself. Maybe we'll change your mind either right now or sometime down the road. So this is a fun conversation. I'm sure you'll like it. And let's go. You don't need a passport to taste the world's most luxurious beef. Just head to

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The BZ isn't just electric. It's Toyota Electric. We make it easy. Toyota, let's go places. David Chalmers, welcome to the Minescape podcast. Thanks. It's great to be here. So I've discovered in my brief history of having philosophers on the podcast

that there's a lot to say, that we have a lot of ground to cover. I know that you especially have all sorts of interests. Let's just jump right into the crowd-pleasing things that we can talk about. You're one of the world's experts on the philosophy of consciousness. You, I believe, are the one who coined the phrase the hard problem of consciousness. So how would you define what the hard problem is? The hard problem of consciousness is the problem of explaining how physical processes in the brain somehow give rise to subjective experience. So when you think about the mind, there's a whole lot of things that need to be explained.

some of them involve our sophisticated behavior, all the things we can do, we can get around, we can walk, we can talk, we can communicate with each other, we can solve scientific problems, but a lot of that is a level of sophisticated behavioral capacities, things we can do. And when it comes to explaining behavior, we've got a pretty good bead on how to explain it. In principle, at least, you find a circuit in the brain, a complex neural system, system, which maybe perform some computations, produces some outputs, generates the behavior. Then in principle, you've got an explanation. It may take a century or two to work out the details, but that's roughly the standard model

in cognitive science. And you've wrapped this together as the easy problem? Yeah. So this is what 20 or years ago I called the easy problem. Slightly tongue in cheek. Of the mind and of consciousness in particular, roughly referring to these behavioral problems. problems. Nobody thinks they're easy in any ordinary sense. The sense in which they're easy is that we know that we've got a paradigm for explaining them. Find a neural mechanism or a computational

mechanism that's a kind of thing that could produce that behavior. In principle, find the right one, tell the right story, you'll have an explanation. But when it comes to consciousness, to subjective experience, it looks as if that method doesn't so obviously apply. I mean, there are some aspects of consciousness, which are roughly speaking, behavioral or functional. You could use the word consciousness for the difference between being awake and responsive, for example, versus being asleep, or maybe just for the ability to talk about certain things I can talk about the fact that, hey, there's Sean Carroll. There are some books over there. and I'm hearing my voice, and those are some reports.

Explaining those reports might also be an easy problem, but the really distinctive problem of consciousness is posed not by the behavioral parts, but by the subjective experience, by how it feels from the inside to be a conscious being. I'm seeing you right now. I have a visual image of colors and shapes that are sort of present to me as an element in the inner movie of the mind.

I'm hearing my voice. I'm feeling my body. I've got a stream of thoughts running through my head. And this is what philosophers call consciousness or subjective experience. And I take it to be one of the fundamental facts about ourselves that we have this kind of subjective experience. But then the question is, how do you explain it? And the reason why we call it the hard problem is it looks like the standard method of just explaining behaviors and explaining the things we do doesn't quite come to grips with the question of why is their subjective experience.

It seems you could explain all of these things we do, the walking, the talking, the reports, the reasoning. And so why doesn't all that go on in the dark? Why do we need subjective experience? That's the hard problem. So sometimes I hear it glossed as the question of what it is like to. to be a subjective agent, to be a person. That's a good definition of consciousness, actually first put forward, or at least made famous,

by my colleague Tom Nagel here at NYU in an article back in 1974 called, What is it like to be a bat? And his thought was, well, we don't know what it's like to be a bat. We don't know what a bat's subjective experience is like. It's got this weird sonar perceptual capacity, which doesn't really correspond directly to anything that humans have, but presumably there is something it's like to be a bat.

A bat is conscious. So, and most people would say on the other hand, there's nothing it's like to be a glass of water. Say, if that's right, then a glass of water is not conscious. So this, what it's like way of speaking, way of speaking is a good way, at least, of serving as an initial intuition pump for what is the basic difference we're getting at

between systems which are conscious and systems which are not. And the other word that is, sometimes invoked in this context is qualia, the experiences that we have, like there's one thing that is it is to see the color red, and a separate thing, if I get it right, to have the experience of the redness of red. Yeah, this word qualia, my sense is it's gone a little bit out of favor over the last, say, 20-odd years, but maybe 20 years ago you heard a lot of people speaking of qualia as a word for the sensory qualities that you come across in experience. And the paradigmatic ones would be the experience of red versus the experience of green. You know, you can raise all

this familiar questions about this. How do I know that my experience of the things we call red is the same? Maybe it's the same as the experience you have when you're confronted with the things we call green. You know, maybe your internal experiences are swapped with respect to mine. And people call that inverted qualia. That would be, you're red as my green. Or pain would be another example of the singular in Latin is quali. So the feeling of pain would be a quali. I'm not sure that these qualities are all there is, though, to consciousness. And maybe that's one reason why it's gone out of favor.

There's also maybe an experience to thinking and to reasoning and to feeling. It's much harder to pin down in terms of sensory qualities. But there's still, you might think, something it's like to think and to reason, even though it's not the same as what it's like to sense. I want to just for a little bit talk about this question of whether or not you and I have the same experience when we see the color red. I'm not sure I know what that could possibly mean for it to be either the same experience or a different experience. I mean, one is going on in my head, one is going on in your head. In what sense could they be the same?

But maybe when I say that, it's just a reflection of the fact that there's a hard problem. Well, we know that some people, for example, to be a much easier case, some people are colorblind. Right. They don't even make a distinction between. red and green. Most people have a red green access for color vision and a blue yellow axis and something like a brightness access. But some people, due to things going wrong and their retinal mechanisms, don't even make

the distinction between red and green. So I've got friends who are red green, colorblind. I'm often asking, you know, what is it like to be you? Is it like you just see everything in shades of blue and yellow and you don't get the reds and greens or is it something different entirely? But we know what it's like to be them can't be the same as what it's like to be us. Because, for example, reds and greens, which are different for us, are the same for them. So there's got to be some difference between us as a matter of logic.

My red can't be the same as their red and my green can't be the same as... If my red was the same as their red and my green was the same as their green, and their red was the same. We know their red is the same as their green. Then my red couldn't be different from my green, but it is. So as a matter of logic, there has to be some difference there. But isn't... So one way out is just...

Well, everybody who is different from everybody else, their experiences are different. I guess the question then is, in what sense could they ever be the same? What is it? What is the meaningfulness? And I can imagine some kind of operational sameness, right? Like you say the word red when you see the word red in that behavioral sense, but that's exactly what you don't want to count. Yeah, so I guess intuitively most people think that we can, you know, at least grasp the idea

that my red is the same as your red. and then it's an empirical open question, but if they are, in fact, exactly the same, I mean, you're saying, well, it is unclear how you could operationalize that matter. Now, you might say, I'm a scientist, I want an operational test. On the other hand, I'm a philosopher,

and I'm very skeptical of the idea that you can operationalize everything, that a hypothesis has got to be operationalizable to be meaningful. I mean, there was a movement in philosophy in the first part of the 20th century, logical positivism or logical empiricism where they said the only meaningful hypotheses are the ones we can test. And for various reasons, that turned out to have a lot of problems, not least because this very philosophical hypothesis of verificationism turned out not to be one that you could test. There's a renaissance of logical positivism on philosophy Twitter these days.

Oh, is that right? Rudolf Kahnap, who was one of the great logical positivists, is one of my heroes. I read a whole book called Constructing the World that was partly based around some of his ideas. Nonetheless, verificationism is not one of the ones. And I think when it comes to consciousness in particular, we're dealing with something essentially subjective. I know I'm conscious not because I measured my behavior or anybody else's behavior. It's because it's something I experience directly from the first person point of view. I think you're probably conscious, but it's not as if I can give a straight out operational definition of it. If you say you're conscious, then you're conscious.

It's like, who's to say? Most people think that doesn't absolutely settle the question. Maybe we'd come up with an AI that says it's conscious. And, okay, well, that would be very interesting, but would it settle the question of whether it's having subjective experience? Probably not. Well, so Alan Turing tried, right? The Turing test was supposed to be a way to judge what's conscious from what's not.

What are your feelings about the success of that program? I think it's not a bad, I mean, of course, no machine right now. remotely close to passing. You might as well say what the Turing test is. Yeah, so the Turing test is the idea that it's basically a test to see whether a machine can behave in a manner indistinguishable from a normal human being, at least in a verbal conversation over, say, you know, text messaging and the like. And Turing thought that eventually will have machines that pass this test, that is, they're

indistinguishable from, say, another human interlocutor over our. of conversational testing, then he didn't say at that point, then machines can think. What he said was, at that point, the question of whether machines can think becomes basically meaningless. And I've provided an operational definition to substitute for it. So once they pass this test, he says, that's good enough for me. When Toyota builds an electric vehicle, we don't start with a blank slate. We start with everything we know.

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But it turns out that consciousness is one of the things that we value. A, it's one of the central properties of our minds. And two, many of us think it's what actually gives our minds, gives our lives, meaning, and value. If we weren't conscious, if we didn't have subjective experience, then we'd basically just be, you know, automata for whom nothing has any meaning or value. So I think when it comes to the question, once we develop more and more sophisticated AIs, the question of whether they're conscious is going to be absolutely central to how we treat them, to whether they have moral status, whether we should care, whether they continue to live or die,

whether they get rights, and so I think many people think if they're not having subjective experiences and they're basically machines that we can treat the way we can we treat machines, but if they're having conscious experiences like ours, then it would be horrific to treat them the way we currently treat machines. So, yeah, I mean, if you just simply operationalize all those questions, then there's a danger, I think, that you lose the things which are really, the things that we really care about. And just so we can get our sort of background assumptions on the table here, for the most part, neither you or I are coming from a strictly dualist perspective. We're not trying to explain consciousness in terms of a Descartian disembodied immaterial mind that is a separate substance, right? I mean, we want to at least as the first hypothesis say that you and I are made of atoms, we're obeying the laws of physics, and the consciousness is somehow related to that,

but not an entirely separate category interacting with us. Is that right? Is that fair? Yeah, although there's different kinds and different degrees of dualism. I mean, my background is very much in mathematics and computer science and physics, and all of my instincts, my first instincts, are materialist to try to explain everything in terms of ultimately in terms of the processes of physics. And we explain biology in terms of chemistry and chemistry in terms of physics.

And this is a wonderful great chain of explanation. But I do think when it comes to consciousness, this is the one place where that great chain of explanation seems to break down, roughly because when it comes to biology and chemistry and all these other fields, the things that need explaining are all basically these easy problems, of structure and dynamics and ultimately the behaviors of these systems, when it comes to consciousness, we seem to have something different that needs explaining. And I think that the standard kinds of explanations say that you get out of physics-derived sciences, physics, chemistry, biology,

neuroscience, and so on, just ultimately won't add up to an explanation of subjective experience because it always leaves open this further question. Why is all that sophisticated processing accompanied by consciousness, by subjective experience. That doesn't mean, though, we suddenly need to say it's all properties of, say, a soul or some religious thing which has existed since the beginning of time, and we'll go on to continue after our death. People sometimes call that substance dualism. Maybe there's a whole separate substance that's the mental substance

and somehow interacts, connects up with our physical bodies, and interacts with it. Yeah, that view is much harder to support. to connect to a scientific view of the world. But the direction I end up going is what people sometimes call property dualism, the idea that there are some extra properties of things in the universe. I mean, this is something we're used to, in physics already,

people of, you know, maybe around the time of Maxwell, we had physical theories that took space and time and mass as fundamental, and then Maxwell wanted to explain electromagnetism, and there was a project of trying to explain it, in terms of space and time and mass. So, no, it turns out it didn't quite work. You couldn't explain it mechanically, and eventually, we ended that positing charge as a fundamental property

and some new laws governing electromagnetic phenomena. And that was just an extra property in our scientific picture of the world. So I'm inclined to think that something not exactly analogous to that, but at least analogous to that in some respects, is what we have to do with consciousness as well. Basically, explanations in terms of space and time and mass and charge and whatever the fundamentals are in physics these days are not going to add up to an explanation of consciousness. So we need another fundamental property there as well. And one working hypothesis is let's take consciousness as an irreducible element of the world and then see if we can come up with a scientific explanation of it.

Good. I think this is, I mean, we should absolutely be open to that. I don't go down that road myself. I don't find it very convincing. But maybe, you know, in the next 45 minutes you'll convince me. So I do want to get there. But let's lay a little bit more groundwork first. So one of the things that a lot of the statements I'm going to be making over the course of the chat are of the form.

I think this is right, correct me wrong. So I think one of the things that makes the hard problem hard is just the fact that you can't even imagine looking at neurons doing something and saying, aha, that explains it. Is that fair to say? Yeah. I would say that when you appeal to neural activity and explaining phenomena, there's a paradigmatic way that works. We see how those neurons serve as a mechanism for performing some function, ultimately generating some behavior. That is the paradigmatic appeal to neurobiology in explanation.

And it just looks like any explanation of that form is not going to add up to an explanation of consciousness. It explains the wrong thing. It will explain behavior. but those were the easy problems explaining consciousness was something distinct. That's the hard problem. So you think that even if, and we're very far away from this, but even if neuroscientists got to the point where for every time that a person was doing something, we would all recognize as having a conscious experience,

even if it was silent, you know, experiencing the redness of red, they could point to exactly the same neural activity going on in the brain. You would say, yes, but this still doesn't explain my subjective experience. Yeah, that's, in fact, very important research program going on right now in neuroscience, and people call it the program of finding neural correlates of consciousness. The NCC, for shorthand, we're trying to find the NCC that neural system or systems is active precisely when you're conscious and that correlates perfectly with consciousness, which is a very, very important research program, but it's really,

as it stands, a program for correlation, not for explanation. So we could know that, say, when certain special kind of neuron fires in a certain pattern, that that neural pattern always goes along with consciousness. But then the next question then is why? Explain that fact. Why is it that this pattern gives you consciousness? And as it stands, nothing that we get out of the neural correlates of consciousness program in neuroscience comes close to explaining that matter.

And I think a lot of people, as they start to think about this, you basically need some further fundamental principle. that connects the neural correlate of consciousness with consciousness itself. I mean, Giulio Ternoni has developed a theory, integrated information theory, where he says consciousness goes along with a certain mathematical measure of the integration of information that he calls FI. And the more FI you have, the more consciousness you have. And FI is a mathematically and physically respectable quantity.

It's very hard to measure, but in principle. But you can define it. It could be measured. I mean, there's questions about whether it's, actually well defined in terms of the details of physics and physical systems, but it's at least halfway to being something. Right. Something definable.

But even if, even if he's right, that phi, this informational property of the brain correlates perfectly with consciousness, there's still the question of why. Why, prima facie, it looks like you could have had a universe with all of this integration of information going on and no consciousness at all. And yet, in our universe, there's consciousness. How do we explain that fact? Well, I think what I regard is the scientific thing to do at this point to say, okay, well, in science, we boil everything down to fundamental principles and fundamental laws. And if we need to postulate a fundamental law that connects, say, if I with consciousness, then that's great.

And then maybe that's going to end up being the best we can do. Just as in, say, in physics, you always end up with some fundamental laws, whether it's a principle of gravitation or a grand unified theory. that unifies all these different forces, you still end up with some fundamental principles. And you don't explain them further. Something has to be taken as basic. And the question, of course, we want to minimize our fundamental principles and minimize our fundamental properties as far as we can. But, you know, Occam's razor says, don't multiply entities without necessity. Every now and then, there's necessity. Maxwell had necessity. And if I'm right, there's necessity in this case, too. And you hinted at, or you sort of alluded to an idea that is one of your most famous philosophical thought experiments just there where you say,

you can imagine a system with whatever file you want, but we wouldn't call it conscious. So you take this idea to the extreme and say there can be something that looks and acts just like a person, but doesn't have consciousness. So this is the philosopher's thought experiment of the zombie. The philosopher's zombie is somewhat different from the ones you find in, Hollywood movies are in Haitian voodoo culture. The ones in voodoo culture, as far as I can tell,

are mostly beings that have been given some kind of poet, people have been given some kind of poison, and somehow seem to be lacking autonomy, volition, a certain kind of free will. The ones in Hollywood movies are beings which are a lot like us,

but they're dead and reanimated. And they want brains. The philosopher's zombie is a creature which is exactly like us, functionally and maybe physically, but isn't conscious. Now, it's very important to say nobody, certainly not me, is arguing that zombies actually exist,

that, for example, some human beings around us are zombies. Actually, I did once meet a philosopher in Dublin, who was very concerned that quite a lot of philosophers actually were zombies. They weren't conscious at all. And I was a little bit insulted by this. He seemed to be worried about me. He took me to lunch. He might explain a lot.

He took me to lunch and he asked me a whole lot of questions about consciousness. Your inner experiences. And at the end he said, okay, you pass. I think you're conscious. Okay, but a zombie could also pass, right? So is it right to say that a zombie, I don't think it'd be, we let you finish your definition yet, but a zombie would be behaviorally the same, but yeah, behaviorally the same, but no conscious experience.

There's nothing it's like to be a zombie. a good way to work up to this is by thinking about, say, some sophisticated artificial intelligence system that produces lots of intelligent responses. Maybe it talks to you, maybe an extension of, you know, Alexa or Siri, who carries on a very sophisticated conversation with us, but most of us are not inclined to think. Let's say Alexa and Siri, as they stand, are conscious that they're having subjective experiences. Okay, now put Alexa in a body like Sophia. The robot. there's a robot that's out there with a very sophisticated conversational system, make her smarter and smarter.

And then there's at least an open question. Is she going to be conscious? And we can make sense of the hypothesis that she's conscious. We can also make sense of the hypothesis that there's not, that she's not. The extreme case is going to be a complete physical and functional duplicate of a human being, with all the brain processing intact, all of the behavior, maybe even a complete physical duplicate of Sean Carroll. And I think I can make sense of the hypothesis when I talk to you

that there be such a being who's not conscious. Zombie, Sean Carroll. Now, I'm very confident that you're not zombie Sean Carroll. I think most human beings are enough like me that they're going to be conscious. But the point is, at least seems logically possible. It seems there's no contradiction in the idea of a being physically just like you without consciousness. And that's just one way of getting at the idea that somehow, well, where you do have consciousness, then something special and extra has to be going on.

So I mean, you can just put the hard problem with consciousness as the problem of why aren't we zombies. Right. What differentiates us from zombies. And with some trepidation, let me ask the question how the difference between possible and conceivable comes into the zombie argument. Yeah, I mean, for us of us like to talk about possible worlds. what goes on in different possible worlds. And there's a possible world where Hillary Clinton won the election in 2016, and there are possible worlds where the Second World War never happened.

These are all maybe terribly distinct possible worlds. They might, for example, share roughly the same laws of physics as ours, maybe small differences in the initial conditions. Some of us think we can also make sense of worlds with different, laws of physics and different laws of nature. Maybe there are classical possible worlds. Maybe there are possible worlds that are two-dimensional, like Conway's Game of Life, with just bits fluttering on a surface governed by simple rules. So, yeah, there are very distant possible worlds with very different laws of nature. And the broadest class is maybe something

like the logically possible worlds corresponds roughly to what we can conceive of, or what we can imagine. I mean, maybe there are even worlds we can't imagine, like worlds where two plus two is five. That's getting a bit too far even for things really start to go haywire around that point. But as long as we don't have contradictions, then we can at least entertain possible worlds. So I'm inclined to think the zombie hypothesis looks to me perfectly coherent and perfectly conceivable. There is a universe which is physically identical to ours, but in which nobody has subjective experience. That's an entire zombie universe, if you like. Conscious experience never flickers into existence.

There's just a whole bunch of sophisticated behavior. I don't think our universe is like that, but it seems to make sense. And one way to pose the hard problem is saying what differentiates our world from that world. When Toyota builds an electric vehicle, we don't start with a blank slate. We start with everything we know. The BZ brings Toyota's proven engineering to electric, with impressive range, intuitive technology and Toyota reliability, BZ reflects decades of experience, reimagined for what's next. The BZ isn't just electric, it's Toyota Electric. We make it easy. Toyota, let's go places.

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Search Fremont Street Experience for the full lineup and dates. Right. So where I come down here is I don't think that zombies are conceivable. And I'm very happy to be talked out of this. Because I think that I talked to you a couple years ago before I wrote the big picture, and I was not quite as sharp in my thoughts about this. So like you just said, we could imagine a literal physical copy of our world. So that includes all the people in it, all the atoms that they're made of.

And you do think that, as far as we know, the atoms in my body just obey the laws of physics, as we know them, right? So in that world, I would be here in that world, but without consciousness, without experience. I would be here. I'd be a zombie, but I would be acting and saying exactly. the same thing as I'm acting and saying now. Is that right? Yep. Okay. And so if you in that world were to ask me if I were conscious, I would say yes. Yeah. And presumably there is a sensible way in which I could say, I say yes, because I believe it to be true. Is that fair? Yeah, it's a complicated issue whether zombies actually believe anything, but they've got zombie analogs of beliefs at the very least.

So, I mean, the most basic way to put it then is how can I be sure that I'm not a zombie? If all the things that I say and do are exactly what a zombie would say and do. Well, I think this is a very good argument that I can't be sure that you are not a zombie because all I have access to with respect to you is, you know, your behavior and your functioning and so on. And none of that seems to absolutely differentiate you from a zombie. I think the first person case is different because in the first person case, I'm kind of, conscious. I know that I'm conscious. I know that more directly than I know anything else. I mean, Descartes said, you know, way back in the 1640s, this is the one thing I can be certain of.

I can doubt everything about the external world. I can even, I can doubt there's a table here. I can doubt. There's a body. There's one thing I can't doubt. That's that I'm thinking. Or I think, he could even better have said that I'm conscious. He said, I think, therefore, I am. So therefore, I don't, I can't doubt my own existence. So I would take, it just, I think, I just, I think it's natural to take consciousness as our primary epistemic datum. So whatever you say about zombies and so on, I know that I'm not one of them because I know that I'm conscious. But I think that my worry about exactly that is that, so like you said, my argument certainly would make you wonder whether I am conscious. I think it also makes me wonder whether I'm

conscious because I think that the zombie me would, because the zombie me would behave in exactly the same way. It includes, you know, writing all the bad poetry I wrote in high school and, you know, crying at movies, at Wally and so forth, and, you know, petting my cats. Like, all of these things, the zombie would do in exactly the same way that I do. If you ask that zombie me, are you conscious? It would say, yes, and here's why. It would give you reasons. I don't see how I can be sure that I'm not that zombie. I think, to be fair, this is, you're, put your finger on, I think, the weakest spot for the, for the zombie, and for ideas that come from it.

In my first book, The Conscious Mind came out about 20 years ago. I had a whole chapter on this that I called The Paradox of Phenomenal Judgment that basically stems from the fact that my zombie twin in that universe next door is going around doing exactly the same things that I'm doing and saying the same things that I'm saying, and even writing a word-for-word identical book called The Conscious Mind, arguing that consciousness is irreducible to, to physical processes. And I'd say, well, and that's, I mean, you know, a lot of strange things go on in possible worlds.

We shouldn't take them too seriously, but I'd say that, yeah, in the zombie universe, the right view is what philosophers call a limitivism, that there is no such thing as consciousness. The zombie is in fact making a mistake. I think there is a respectable program about consciousness in our world that says we're basically in the situation of the zombie. And lately, just over the last two or three years, actually, there's been a bit of an upsurge of people really thinking seriously about this view which has come to be known as illusionism. Okay. The idea that consciousness is some kind of internal, introspective illusion.

After all, if you think about what's going on with the zombie, the zombie thinks it has special properties of consciousness, but it doesn't. All is dark inside. So then say, that's actually our situation. It's like, it seems to us, do we have all these special properties, those qualia, those sensual. those sensory experiences, but we're not. All is, in a way, dark inside for us as well, but there's just a very strong introspective mechanism that makes us think we have these special properties.

That's illusionism. Now, most people find it impossible to believe that consciousness isn't an illusion in that way. On the other hand, the view does have the advantage of predicting that you would find it impossible to believe if it's a good enough mechanism that makes you focus on this. So actually lately, I've been thinking about this a lot, and I wrote an article called the Meta Problem.

of consciousness that's just come out in the Journal of Consciousness studies. The hard problem of consciousness is why are we conscious? How do physical processes give rise to consciousness? The meta-problem of consciousness is why do we think we're conscious? Why do we think there's a problem of consciousness? And the great thing about the meta-problem is remember the hard problem, the easy problems are about behavior, the hard problems about experience. Well, the meta-problem is a problem ultimately about behavior. It's about the things we say and things we do. Why do people go around writing books about this?

Why do they say, I'm conscious, I'm feeling pain. Why do they say I have these properties that are hard to explain in functional terms? That's a behavioral problem. That's an easy problem. Maybe ultimately there'll be a mechanistic explanation of that. And that would, of course, be potential grist for the illusionists mill. Once you have the mechanisms that explain why we say all these things in physical terms, you could then try and turn that round into an explanation of,

of, you could then call that solution to the meta problem an explanation of the illusion of consciousness. Some people will still find it unbelievable, but again, the view predicts that. And if I wanted to know why I feel puzzled by the hard problem of consciousness, is that the meta-meta-problem of consciousness? Oh, I think that, maybe that's still the meta-problem.

Why do you find consciousness puzzling is certainly one central aspect to the meta-problem? There are all these things that we seem to feel and say, my red could be your green. I can imagine zombies. Consciousness seems non-physical. Those are all behaviors. Explain those behaviors. And maybe you've explained at least the higher order judgments about consciousness.

Now, my own view is that even that wouldn't add up to an explanation of consciousness. But I think at the very least, understanding those mechanisms might tell us something very, very interesting about the basis of consciousness. So I've been recommending this as a research program, a neutral research program for everyone, philosophers, scientists, and others. Neutral in the sense, it's not presuming any conclusion about what the answer will be. Exactly. You didn't be materialist. You didn't be dualist. You didn't be illusionists. You didn't be, you know, this is just basically an empirical research program. Here are some facts about human behavior. Let's try and explain them. Furthermore, philosophers, psychologists, neuroscientists, AI researchers could all in principle get in on this.

And I think there's gradually a building, I mean, there's already going to be a target article, a symposium, a journal of consciousness studies with a whole bunch of people from all those fields getting in on it. So I'm hoping this at least turns out to be a productive way to come with the question. Of course, it won't be neutral forever. Eventually we'll have some stuff and then, you know, some results and some mechanisms. And then the argument will continue to rage between people who think the whole thing's an illusion and the whole thing's real. We should say, though, that aside from elimitivism and illusionism, which are fairly sort of hard, hardcore on one side, or forms of dualism, which could be on the other side, there is this kind of emergent position that one can take, is what I want to take in the big picture and

so forth, which is physicalist and materialist at the bottom, but doesn't say that therefore things like consciousness and our subjective experiences don't exist or our illusions. They're higher order phenomena like tables and chairs. They're categories that we invent to help us organize our experience of the world. Yeah, you know, my view is that emergence is a sometimes used as kind of a magic word to make us feel good about things that we don't understand. How do you get from this to this? Oh, it's emergent. It's emergent.

But what really do you mean by emergence? I think I've read an article on emergence where I distinguished weak emergence from strong emergence. Weak emergence is basically the kind you get from, you know, low-level structure dynamics, explaining higher-level structure, dynamics, the behavior of a complex system, traffic flows in a city, the dynamics of a hurricane. I mean, you get all kinds of strange and surprising and cool phenomenon emerging at a higher level. But still, it's ultimately, once you understand the low-level mechanisms well enough, the high-level ones just follow transparently. It's just low-level structure, giving you high-level structure according to the following of certain simple low-level rules.

You could put it on a computer and simulate it. Exactly. But when it comes to consciousness, it looks like, well, when it comes to the easy problems of consciousness, those may well turn out to be emergent in just this way. There may turn out to be low-level structural or functional mechanisms that produce these reports and these behaviors and lead to systems sometimes being awake. And no one would be surprised if these were weakly emergent in that way. But none of that seems to add up to an explanation of subjective experience, which just looks like something fundamentally new. This is, philosophers sometimes talk about emergence in a different way, a strong emergence, which actually involves something fundamentally new emerging via new fundamental laws. Maybe there's a fundamental law that's saying, says when you get this information being integrated, then you get consciousness.

I think consciousness may be emergent in that sense, but that's not a sense that ought to help the materialist. I think if you want consciousness to be emergent in a sense that helps the materialist, you have to go for a weak emergence. And that's ultimately going to require reducing the hard problem to an easy problem. So I think everyone has to make hard choices here. And I don't want to let you off the hook of just saying, it's all ultimately going to be the brain and a bunch of emergence.

There's a respectable materialist research program here that has to involve ultimately turning the hard problem. All you're going to get out of physics is ultimately more and more structure and dynamics and functioning and so on. So for that to turn into an explanation of consciousness, you need to find some way to deflate what needs explaining in the case of consciousness, ultimately to a matter of behavior and a matter of functioning, and maybe say that extra thing that seems to need to explaining, that's an illusion.

And, you know, people like, Danet, I respect greatly, has tried to do this for years, for decades. That's been his research program. At the end of the day, most people look at what Dennett's come up with and they say, nope, not good enough. You haven't explained consciousness. If you can do better, then great. Whereas, so to move more in the direction of what you're positively advocating for, at least, I mean, you've always been very careful to positively advocate for not that much, because this is, as you say, a hard problem. We don't know the answers yet. We don't need to move forward by sort of insisting this must be the right answer. So you've been open-minded, but you're at least open-minded about this property dualism that you talked about, and that sort of one version of that leads us into panpsychism. So could you explain these two concepts? Yeah, so I'd say that I've explored a number of different positive views on consciousness.

What I haven't done is committed to any of them. I see various different interesting possibilities, each of which has big problems, has big attractions, but also big problems to overcome. So I've tried to explore some of those one at a time. One of the possibilities is panpsychism, the idea that consciousness goes right down to the bottom of the natural order. pan-psychism. I mean, pan means all, psych means mind. So it's basically saying everything has a mind. Taken literally would imply that, you know, people have minds, particles have minds, but also tables and numbers have minds. Sorry, do we have to say have minds, or can we just get away with saying something like have mental properties as well as physical ones?

Yeah, if that makes you feel better. It might feel a little bit better. Yeah. Have experiences. We could say there's something like it's like to be them. Well, I don't know. I mean, do we want to saying an electron has experiences? I think panpsychism taken literally has that consequence. By the way, most panpsychists don't say that tables or rocks or numbers have minds, but they're typically that their biggest commitment is to fundamental physical entities

have a mind. So if you want to say, now there's a weaker view, you might want to say actually something it's like to be an electron. Electron doesn't have experiences. It merely has some proto version of experience, some predecessor of experience. Maybe electrons are, proto-conscious. Then there's a view called pan-proto-psychism that could maybe seem a little bit

less insane to you. I mean, the trouble, of course, one of the troubles with pan-psychism is it seems very counterintuitive because we don't naturally think that electrons have consciousness. And there's not a whole lot of direct evidence in favor of it. On the other hand, you might say there's also not a whole lot of direct evidence against it. It's not like we've got any experimental evidence that electrons are not conscious. Well, let me, rather than harp on that, Let me just try to figure out what it would mean for electrons to have minds or experiences or consciousness. It certainly can't mean another quantum number in the physical sense, right? They can't have, you know, happy electrons and sad electrons.

That would change much of particle physics in bad ways. So is it that the, is it some kind of epiphenomenalism? Do the happiness or sadness, if we want to call it that, just go along with the electron? what determines what the electron is feeling? The way I think the best option for a panpsychist here is, yeah, you don't need a whole bunch of extra new laws of physics for the consciousness at the basis. Rather, it's consciousness that's fundamentally

playing the causal role for the physics that we know. I mean, it's a point that's often been made about physics. It's fundamentally, the science of physics is fundamentally structural or mathematical. Everything is basically explained by how it relates to other things. Maybe quantum mechanics gets messy and everything else in contemporary physics

gets even messier. So let's just start with classical physics that characterizes, you know, particles, positions in space and time, with some mass, with some forces that operate on them. What is mass in classical physics? Well, it's this thing which is subject to the laws of gravitation and the laws of motion and that, you know, is involved in force,

in a certain way. Nothing here tells us what mass is in itself. Rather it explains mass by the way that particles with mass interact with other particles. What its role is. So it's all a giant structure. Physics does a great job of characterizing this structure. And then you want to, that raises the question. Well, what is? What is the intrinsic nature of mass? Well, one thing someone might say is, I doesn't need to have an intrinsic nature. It's just a giant relational web. And that's a respectable view, which I think, you know, maybe some people think it doesn't make sense. Other people think it makes sense. But here's another possibility.

Structural realism. Structural realism is what it gets called in contemporary philosophy of science. An ontological structural realism says that's all there is in the world. A giant web of relations. Right. Okay. But the other possibility, people sometimes speak of epistemological structural realism, what physics tells us is the structure,

but there may be some intrinsic natures underlying the structure. And as far as I can tell, that's a respectable possibility as well, that mass does have an intrinsic nature, that when two things with mass interact, they've got some intrinsic properties that govern that interaction. And of course, the panpsychist idea is to say maybe that intrinsic property is consciousness or experience or maybe proto-experience. Or mind in essence, yeah. That somehow mind lies at the bottom, at this bottom level serving as the intrinsic properties

that underlie physical structure. If that's the role it plays, we don't suddenly need to revise. physics, the structure of physics, can stay exactly as it was. We're just going to have some intrinsic properties, the ground, that structure. Then you might say, well, now how is mind making a difference? Well, it's not like it's making a difference by suddenly having new laws in the picture for minds. Rather, it's making a difference by being the thing, the grounds, the physical web. Any time one particle's mass interacts with another, two particles, say, attract each other by gravitational force. On this picture, it's ultimately going to be

there are mental properties doing the work. OK, so we're not saying, again, in this picture, which may not be right, but we're not saying that the mental properties affect the physical behavior of the electron. So a physicist, I know some personally, might worry that this isn't saying anything at all because still everything the electrons do is just governed by the laws of physics because these mental properties don't affect it. But you're saying that's just the wrong way to ask the question, the kinds of things that are being explained, by this positing of a mental character underlying everything

are not the behavior of the electrons, but something deeper and something that kind of flowers once you get complex organisms that we recognize as conscious. Does the experience affect the behavior in one sense? Yes, and another sense, no. I mean, it's certainly true. This is not going to be so exciting for a current physicist and that all the current physics can stay the same.

Physics with the experience underneath it or without it. You might think it's a good thing. We have all the excitement we need. Yeah, if we had to revise physics too, then it would give rise to all kinds of extra crazy complexities. That said, this is more of an interpretation of current physics and of what's going on in the world underneath current physics. And it's ultimately saying that what is doing the work in physics at the bottom level is these intrinsic properties of mind or consciousness. The fundamental laws, which we think of as laws, say, you know, connecting mass and mass or mass and motion or whatever, ultimately going to be laws connecting little bits of experience in this structure.

From the outside, all we see is the structure. We give it a mathematical description, and we call that the laws of physics, and it's great. But in reality, what's underlying it, you know, we're used to the idea that what underlies a physical theory may involve more than what actually gets, that we see in experimental results. On this hypothesis, what underlies it in reality is a whole bunch of minds or experiences pushing and pulling each other. Is this wildly speculative? Of course it is.

But is it ruled out by anything we know? Yeah, I think not. So I think it's, in a speculative vein, it's at least a philosophical view to take seriously. With the RAM declaration of deals, we're pledging our allegiance to the American people with great deals on the RAM 1500. Back with the legendary Hemi V8 and the RAM heavy duty.

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Toyota, let's go places. And it must be tempting to look toward quantum mechanics for a place to implement these kinds of ideas. Yeah, quantum mechanics is, of course, it's a magnet for anyone who wants to find a place for crazy properties of the mine to interact with the... in the physical world because quantum mechanics is so ill-understored, then it does have suggestive properties that connect,

that may seem to connect to observation or the mind. I would actually not connect, combine quantum mechanics and panpsychism in the most promising role. There are people who connect quantum mechanics and panpsychism, somehow of the right degree of quantum mechanical holism, somehow you could see all those individual experience, might add up to a big experience. Lately, though, I've actually been thinking about quantum mechanics in the context of a different

kind of view, which is more a kind of dualism, with property dualism, with properties of consciousness distinct from properties in physics, but somehow interacting with it. If you're not going to be a panpsychist and say consciousness is present at the bottom level of physics, then consciousness has to be somehow the property of consciousness has to be separate from those other ones. space time, mass charge, and that raises the question now, how does it interact? Either you say it doesn't, it's epiphenomenal, it does nothing, well, that's kind of weird, and consciousness has no effect at all in the physical world, or you say it has an effect

on the physical world, and then the question is how on earth you reconcile that with physics, which doesn't seem on the face of it to have any room for consciousness to play that role. And there is, of course, this one, I would say age-old idea. It can't be an age-old idea because quantum mechanics has only been a real-old. around for a century or so. But this one, old idea that maybe there's at least one kind of fairly traditional interpretation of quantum mechanics where minds could play a role in quantum mechanics, mainly via the process of observation, which collapses the quantum wave function.

Of course, it's very controversial, but it is a very traditional picture of quantum mechanics. So there's two kinds of dynamics of the quantum wave function. function, there's Schrodinger evolution, the normal thing, and there's something weird which happens on measurement. And standard quantum mechanics says make a measurement, the way function collapses. And that's a different thing from Schrodinger evolution. Now, of course, this immediately raises a million questions, like, what on earth is measurement? And why should that get any special treatment? That's the quantum measurement problem.

And that's many people run a mile at that point saying, oh, come, I don't want minds to play a role in physics. Let's try something else, and they find themselves in Everett-style many worlds quantum mechanics or Bohm-style, hidden variables quantum mechanics, or GRW-style collapse quantum mechanics, which doesn't give minds a role. And I think all those programs are great and very interesting, and I'm not against them, but I'm also interested in a possibility which may have been overlooked, which is trying to make rigorous sense of a more face-value interpretation of quantum mechanics. where there is something special that takes place upon measurement.

Now, if you're an average physicist, well, why can we, it just seems very strange to treat measurement as fundamental because that would involve treating the mind as fundamental, and that's not something that everyone wants to do. If, on the other hand, you're inclined to think there's already reason to think, the mind involves something fundamental, and that consciousness is somehow a fundamental element in nature, then that reason to reject the view will not be a good.

reason to reject the view. And the question for me is just can we actually make rigorous mathematical sense of the idea that it's once consciousness comes into the picture that the wave function collapses. Is it fair to associate this view with something like idealism, where you're putting mind as the first thing that creates reality? Maybe there's an idealist version of this, but I would actually think of it as a version of property dualism. That is, the quantum wave function is real. It's got an existence that has nothing to do with the mind. the universe has an objective wave function just as it might on, say, Everett-style view, is rather there's this aspect of the dynamics of the wave function which is affected by the mind.

And under certain circumstances, physical systems will produce consciousness. Under certain circumstances, that consciousness will collapse the quantum wave function. So it's actually, you know, Descartes thought that, you know, the body affects the mind and the mind affects the body. That was classic interactionist dualism. Think of this as an updated version of Descartes in a property dualist framework. You've got the quantum wave function. You've got some dynamics by which the wave function affects consciousness. You've got some laws.

It might be say something like Ternone's integrated information theory. It says when the wave function has enough integrated information, then you get a bit of consciousness. And then you need some other bit of dynamics by which consciousness can affect the wave function. The idea that I was working on this with Kelvin McQueen, a former student of mine, who's now in philosophy and physics at Chapman University in California. And the idea we started working with was there's something special about consciousness or maybe about the physical correlates of consciousness, so that it resists quantum superposition.

Everything in the world, mass and charge, most properties can evolve into quantum, superpositions, but maybe there are some special properties that resist quantum superpositions. Maybe they go into superposition for a moment, but then they always collapse back, or maybe the moment they're about to superpose, they pick a determinate state. And then the thought was, if that happens, say consciousness is like that. Consciousness never enters a superposition. The moment brain processes would be such that they would produce a superposition of consciousness, and somehow they collapse into a definite state.

Right. And then you might see that as an effect of consciousness on the physical processes in the brain that could in principle give you an effect of consciousness in the physical world. And then the question is, for me, ultimately it turns, I mean, it's a wild, it's a weird and speculative picture, of course, but anyone's theory of consciousness is weird and speculative. For me, the question is... It's picking up old ideas from people like Vignor and they've dropped out of favor now, but you want to re-examine that.

Absolutely. So Vigner in 1961, remarks on the mind-body question is probably the Locust Classicus for this. people think they find the idea, hints of the idea, at least in von Neumann. And earlier, in the 1970s, this got associated with, you know, the dancing woo-lee masters and so on, at which point physicists started running a mile from this idea. I think, you know, it has been used in some unfortunate ways. But I just want to examine this idea, see if we can get it on the table as one of the many alternative interpretations of quantum mechanics, which has upsides and, downsides. For me, the question is ultimately, can you give it a good, coherent mathematical dynamics

that works and is consistent with all of our predictions? If that can be done, then we can take it seriously. Now, I should say that the version Kelvin and I started with does have one rather serious problem with the so-called quantum zeno effect. Okay, yeah. Roughly the quantum zeno effect says if you've got some quantities that are constantly being measured, they're always measured so they never enter into super positions, then they never change. So if you constantly measure the position of a particle, it'll never move. I can see where this would be a problem, yes. If consciousness is such, it's constantly never entering into a superposition.

It's at least as if consciousness is never being measured, is always being measured, which means that consciousness can never change. So, for example, if you start out with an early universe with no consciousness, then consciousness will never get a chance to come in. to existence. The moment there's a little glimmer of consciousness, it's going to like, it's going to snap back. Only one tiny little low amplitude part of the wave function will there be consciousness and with probability one, it will snap back to no consciousness.

So consciousness can never evolve. Furthermore, you can never wake up from a nap. If you're unconscious, you'll never get to, you'll be little branches that develop consciousness that'll snap back to unconscious with probability one. That sounds like a good world. Now I like it. Yeah, never waking up from the nap world. Naps go on forever. So, okay, this was a small small problem for the initial simplest version of the theory, which we're now trying to work this into a negative result paper called Xeno goes to Copenhagen, raising the Xeno effect as a problem for a class of interpretations nearby. But then the question is, can that, is there a version

of this you can make work that won't suffer from this Xeno problem? We've been playing around with probabilistic versions and versions where consciousness super poses for a while and collapses back and I'd say we haven't exactly solved the problem yet, but I think there's a, there's at least an interesting class of interpretations here worth taking seriously if you are inclined to take consciousness seriously. And after all, quantum mechanics is enough of a mess that it's worth trying. It's not like there's any interpretations that that is free of problems. So if there's something here that A gives you a perfectly adequate quantum mechanics and B allows a role for consciousness in the physical world, and that would at least be reason to take the view

seriously. And if you are a property dualist, if you believe in mental properties as well as physical properties of stuff, does that have implications for questions like artificial intelligence or, you know, consciousness on a computer? Yeah, I think it doesn't have immediate implications. I mean, some people think that if you're a property dualist, you should think that computers won't be conscious. To me, that's kind of odd.

I mean, we're biological systems who are with brains. somehow we're conscious. So why should silicon be any worse off than, say, brains? I mean, that almost seems like a weirdly materialist idea to privilege the things made of DNA over things made of silicon. Why should that make a difference? I think so dualism is just neutral on the question. The kind of property dualism, I like a fairly, you know, scientific, naturalistic property dualism with fundamental laws of nature. I think it's going to come down to are the properties of matter that get connected to consciousness in our theory of consciousness. Are they going to be more like specific biological properties or are they going to be more

like computational or informational properties? If it's something like Chironi's integrated information that gives you a consciousness, and it looks like that can be present just as much in a silicon system as in a biological system. So in the work I've done at least, I've tried to argue that it's really the computational properties of matter that are relevant to, to, to, consciousness or the informational properties. If that's the case, then an AI system will be able to do the job just as well.

And in principle, we could even replace our neurons. You know, one of the time, the biological neurons by silicon, prosthetic neurons, if they work well enough, we'll be left with a functionally identical system. And I would actually argue that that functional identical system is going to retain the same consciousness throughout. The alternative would be to say that consciousness fades away. fades away or disappears, but that gives rise to all kinds of problems. Right.

And then before I was asking, if I'm sure I'm not a zombie, this leads us to ask if we are sure that we're not a computer simulation, right? This is one of the great problems of philosophy. I mean, Descartes said, how do we know that there's an external world? How do you know you're not being fooled by an evil demon who's merely producing experiences in you as of an external reality? when all of this is just being generated by the demon. Now, the simulation idea is a wonderful 21st century version of Descartes. I mean, as illustrated by movies like The Matrix, I'm still a fan of the depiction of this movie in the Matrix

that really, I think, got quite a lot of this right. How do you know you're not living in a computer simulation? That is, the computer simulation is playing the role of the evil demon, running a model of a world, feeding your brain experiences, when in fact you think you're in an ordinary physical reality, but in fact you're in this computer-generated reality. And the people who wrote movies like The Matrix, they say if this is the case,

then you're basically living a life of illusion and deception. It's not the real world. And none of it is real, which is exactly what Descartes thought about the evil demon. hypothesis. So I've been thinking about this lately, and I do take the simulation idea seriously. I think there's nothing we know with certainty that rules out the idea we're in a computer simulation. The philosopher Nick Bostrom has actually given a statistical argument that we should take it very seriously, that we are in a simulation. Roughly the idea is that any sufficiently intelligent population will have the capacity to create lots and lots of computer

simulations of whole populations. So as long as they go ahead and use their abilities and create computer simulations, then most, the majority of beings in the universe will be simulated beings and not unsimulated beings. And then the thought is, we'll just do the math, do the statistics. 99.9% of beings in the universe are simulated, including a whole bunch who are just like me. What are the odds that I'm one of the lucky ones?

one's at ground zero, the 0.1%. So you might say I should be 999 out of 99.9.9% confident that I'm a simulated being. Now, you can raise issues with the reasoning here and there. One question is would a simulated being be conscious? Some people would say, no, they're not conscious. They'll be zombies. If so, the fact that I'm conscious shows that I'm not in a simulation. You think you're conscious.

Go ahead. But at least, but that's not going to help me because I'm at least on. record is thinking that a simulated system and AI system could be just as conscious as a biological system. So I think all those beings in computer simulations may well be conscious. Maybe it's only 50 percent, okay, even if it's only 50 percent likely they're conscious, then that still should give a big dose of probability to the hypothesis that I'm in a simulation. So that's not going to help. So I think it's actually possible that, you know, I do, I can't rule out that we're in a simulation. Where I want to get off the boat, though, is this idea that simulations are illusions.

Right. That simulations aren't real. I think we could be in a world, which is a simulation. But if so, that doesn't mean that, you know, there's no tables and chairs in the world around us. There's no matter. It's all an illusion. I think what we should say is instead, yeah, we're in a world with tables and chairs and matter. And we've made it, if we're in a simulation, then if we're just kind of, we're just kind of.

However, where in a simulation will have made a surprising discovery about what tables and chairs are made of. They're ultimately made of, say, information and computational processes at the next level down, which may ultimately be realized in processes in the next universe up. But importantly, it's all still real. It's not like, as Descartes thought, a world where nothing around you exists. Yes, the world around me exists. It just has a surprising nature. And this actually connects nicely to the ideas about structural realism.

we were talking about before, that really physics tells you about the structure of the world. It doesn't tell you ultimately but what that structure is made up of. If we're in a simulation, it turns out the structure is exactly, the mathematical structure of our reality, maybe exactly as physics says. It's just that it's all implemented or realized on a computer in the next universe up. So, yeah, the structure of physics is real, so the electrons are still real. They're just ultimately electrons made of bits, made of whatever is fundamental. fundamental in the next universe up.

You said if we ever find out, is there any way we would ever find out? Depends how well the simulation is made, doesn't it? You know, if it's like the one in the Matrix where they gave us some potential ways out, like the red pill. It's a very buggy code. Yeah, that's a dumb way to build a simulation if you ask me, unless you want people to escape. If it's a perfect simulation, we may never find out.

And because of that, I think if we're not in a simulation, we may never be able to prove that we're not in a simulation. Because in a perfect simulation, any evidence, any proof we can get could be simulated. Right. By beings with the same experiences. So I think we'll never get, we'll never know for sure the negative claim we're not in a simulation. It could be that if we are in a simulation, we can get some very decisive evidence for that. You know, if the simulators suddenly move the moon around in the sky and, you know, write big signals.

and we look at our genetic code and we've had messages written in there saying, hey, losers, you're in a simulation. Then we take that to be pretty strong. There is the pre-existing hypothesis of God having done all this, right? It's not that different. God doing these things from our programmers doing these things. Exactly.

And the question of evidence arises for God as well. I mean, we could in principle get decisive evidence that there is a God. It's very hard to get decisive evidence that there's not a God. And you think that it's realistic to think that we can at least imagine doing simulations that are so good that a multiplicity

of intelligent conscious creatures exist there in our simulations. I think so in principle. I mean, I don't see it's just a matter of really of computer power

and of, you know, once we know the laws of physics well enough, presumably we could set up a universe with boundary conditions like, which are allowable boundary conditions

for a universe like us, set up, the differential equation simulators on our maybe we would need to be a quantum computer to be especially to get the quantum mechanics right but then I don't see why in principle

you couldn't get, maybe it'd be hard to get a universe as complex as our universe. Oh yeah, it'd have to be less every level down has to be less right? If our universe is finite has say you know one billion units of complexity then we can't simulate something with one billion units of

complexity but maybe something worth you know one million units of complexity just to not to text the universe. Yeah. Too much. And of course, if we are in the enormous universe that we seem to be in now with enormous resources, that seems to probably it'll have resources to be able to simulate some pretty complicated universes without too much trouble in principle. These kinds of scenarios, whether it's Descartes or simulations or whatever, I mean, can we,

or God creating the universe, can we apply some kind of anthropic reasoning here? ask, you know, if this were the case, would that have some implications for what the universe would look like? And then ask it does or does not look like that. Like I've certainly said, if you want to depend on, if you want to argue that the fine-tuning in the universe of certain fundamental physics parameters that therefore allows for the existence of life is evidence for the existence of God, then you should be consistent in that argument and point out that there are other things about our universe that look wildly unlike you would expect if the point of the universe existing was for our life to exist. Can we say similar things about the purported simulators? Yeah, I mean, you might

worry that most simulations are going to have certain properties and that our universe does or doesn't have those properties. I mean, one thing about a universe is it's enormous. It seems to be enormously big. It's so complicated. Why would you waste your time? If you're going to be making simulations, you might think most simulations are going to be a whole lot smaller and local for many purposes. Why would the simulators be generating universes quite as big and as complex as we are? You might think you're average. Of course, whenever you do make a universe like us, it's going to involve a whole bunch of people making simulations of universes which are simpler in turn,

universes which are simpler in turn more and more of those ever simpler universes. So you might think that actually most universes, going to be very, very simple. Exactly. That's what I would think. Yeah. I think I might have heard Sean Carroll making a version of this point in the past at some point. And then, so, yeah, the very fact that we're in a complicated universe is going to be at least some reason to disfavor the simulation hypothesis. Now, of course, so to go, there's a little bit of back and forth here. One could respond to that by saying, well, we don't know the universe is big. We see galaxies in the sky. But really, we see photocies. tons that have recently reached us.

We don't see the galaxies themselves. Maybe there's nothing more than a few million light years away, and it's all just set up to make us think that. But then we're in some sort of skeptical nightmare. Yeah, what might do we have to lose anything at all? Scepticism. Maybe it's just like everything out to the solar system. Yeah.

We've actually sent probes out to the, you know, to other planets and so on. So the Earth, I don't know, I'm pretty, I think, you know, it's going to be hard to just to simulate like a, like New York City because there's so many people leaving New York City all the time and coming back and the news from the outside. At the very least, you're going to have to have a pretty detailed simulation of the rest of the earth to keep all the newspapers and TV and everything going. But once you move outside the earth, it gets at least a bit easier.

Maybe it's like maybe the moon is just a... I mean, you at least going to need a fairly detailed simulation of the moon because of the role it plays in our lives. But maybe beyond a certain point, you can run a very cheap simulation. Maybe beyond Pluto, we've just got a very cheap simulation of the rest of the universe. And every now and then, maybe the simulators say, they've just made a new discovery, they've discovered a new form of a new way to monitor stuff. They're looking a little bit closer at these exoplanets,

and maybe they scramble and they come up with some new data for us. But maybe that's going to turn out to be much easier to run a cheap simulation. But doesn't even saying these words make you think that maybe this is not the world we live in. That this is not the world. These are all kind of arguments against living in a simulation. Just our universe does look way bigger than it does. You can imagine things the simulators could do, but why are they going to all this trouble? I think it's quite possible, though, that the, I don't know whether our universe is infinite. It's quite possible that the basic universe is infinite. And maybe in the next universe up, they have infinite resources. And it turns out that simulating a large,

finite universes, no problem at all. In fact, they can simulate infinite universes, because in an infinite universe, you'll have the resources to simulate an infinite number of infinite universes without problem. So as long as we don't fall into the trap of thinking that the next universe has to be just like ours, then I think all bets are off. And are there ethical implications for this, or are there implications of this idea for how we should think about ethics? Number one, should we think about ethics in our world differently if we're simulations, and should we worry about making simulations with conscious creatures and treating them well? I think that the ethics of our world didn't be affected drastically by this

anymore than it has to be affected drastically by the theistic hypothesis that we're in a universe with a god. We're still conscious beings, living our lives, treat other people well, make sure they have, by and large, positive conscious experiences rather than the negative ones. maybe we need to think about the impact of our actions on the people in the next universe up. But since we don't really know what that impact is, you might say there's self-interest comes into this. After all, if we want to live on religious hypotheses, people modify their behavior greatly in order they can live forever. We might want to make sure the simulators keep us around. I mean, it does open the possibility of an afterlife, right, if we're in the simulation.

Yeah, I mean, maybe quite naturalist, just as the simulation hypothesis, here has a very naturalistic version of God. It could have a naturalistic version of an afterlife. We already see in TV shows like Black Mirror that people come to the end of their lives and they upload into a simulation and keep going that way. Have you read Ian Banks' culture novels?

I haven't actually, I should. Oh, okay, you certainly should because part of it, it's a small part except for one novel where it plays a major role, but there's this idea that, yeah, they do simulations all the time. There are consciousnesses agents in the simulations, and therefore the intergalactic organization has passed laws, you can't end at the simulations because that would be genocide. But then there's certain very, very bad civilizations

that actually turn them into hells where they torture the AIs that didn't behave in the right way. So I think the ethical questions absolutely get a grip once we start thinking about creating our own simulations. And I'm sure any number of people are going to be tempted, just once we've got the capacity to start up a copy of Sim Universe, running on our iPhone and maybe get a thousand copies up and running and see what happens overnight around the entire history of these universe gather the statistics could be useful for

scientific purposes could be useful for like marketing purposes predicting what products going to do well could just be useful for sure you want to test your different products and see which iPhone is going to right is going to sell the best for sure but yeah I think the ethical issue is really enormous. You're going to be creating universes with billions of billions, trillions, maybe infinitely many people, each of which is living a life as a conscious being. And if there are lives of suffering, then we've done something horrific. And if there are lives of pleasure, then maybe we've done something good. But people talk about, did God create, when creating us, create the best of all possible worlds.

Why was there so much evil? Well, maybe God created many different universes. All the ones that had a net balance of positive experiences over negative experiences. Turned out by creating all those worlds and somehow there was a net positive in creating them. Well, we're going to face questions like this too. Maybe if you want to create experimental worlds where there's suffering, you can only do that when there's a net balance of positive experiences in your simulations to make up for it. Even then, someone's going to say, well, you could have created an even better world

with a bit less suffering and a bit more and a bit more pleasure or fulfillment or satisfaction. So didn't you do something immoral by creating this world? I think we're going to have to face all those questions. They're not going to have easy answers. Okay, speaking of easy answers, two last questions for you, David. One is, you're working on a book. I know it's well in advance, but we can prime our audience to be ready. Do you want to say anything about what the book will be? The focus of the book is very much this set of issues we've been talking about for the last few minutes about simulations and about virtual reality. My working title, probably won't be the final title, but the working title is Reality 2.0, artificial worlds and the great problems of philosophy.

And it's all about exploring philosophical problems like our knowledge of the external world and the nature of reality through the idea of artificial or virtual reality. Are we in a matrix? That's one of them. But also, I really want to develop my own philosophical line, which is virtual reality, simulated reality, is a genuine kind of reality. It's not a fake or a second-class reality. It's a perfectly respectable way for a world to be.

And I think this is relevant, not just for a way-out, speculation, science fiction scenarios like we're living in a simulation, but very practical scenarios like the virtual reality technology that's being developed today, things like, you know, the Oculus Rift, where people enter into virtual worlds and start spending more and more of their time there.

It's easy to imagine, in 50 or 100 years in the future, we're all going to be spending a lot of our time in these virtual worlds. And the question's going to arise is that can you actually lead a meaningful life there? Yeah. And is this, I'm not even sure this is a meaningful question. Is this aimed at a popular audience or professional philosophers or both? I would say both, but I'm absolutely trying to make it as accessible. as possible so anyone can read this book.

You had 10 years, so you can do that. Yeah. I hope they won't revoke it. But yeah, it's meant to be both introducing a whole lot of philosophical ideas, but also putting forward a substantive philosophical view of my own, but roughly this view is a virtual reality is a first-class reality across all of these domains. I think it has bearing on the great philosophical problems. How do we know there's an external world, Descartes' problem?

It has bearings on the question of the relationship between mind and body, and it has bearing on these ethical questions about what makes a meaningful and valuable existence or life of the kind. So I think it's actually a way to come at some of the deepest philosophical problems just through this lens of just as thinking about artificial intelligence. Turns out to shed light on many questions about the human mind. I think thinking about artificial realities, it turns out to shed light on all kinds of questions about the actual natural reality. we find ourselves in.

So that's what I'm trying to do. And the last question is Tom Stoppard. It's one of my favorite living playwrights, playwrights period. He wrote a play called The Hard Problem. How does it feel to have a phrase you coined become the title of a Tom Stopper play? Oh, I was very pleased.

I think actually it was my friend Dan Dennett who sent me an email. He read this in an article and said, hey, there's a Tom Stoppard play coming out called The Hard Problem. I said, great. This has this got something to do with consciousness? But it turns out it does.

And I've actually gotten to know Tom Stoppet a little as a result of this process. He put on, it had its American opening in Philadelphia. A couple of years ago, maybe about a year ago, the Wilma Theater in Philadelphia. And I went down there and did an event with Tom where the two of us were talking on stage about the hard problem of consciousness. The play is very interesting. I'm not convinced it's actually about consciousness. consciousness at its root. It's about a much broader set of questions, some of which involve

consciousness, some of which involve God, some of which involve value. And in fact, in this discussion, it sort of emerged that it's not, that it seemed to me that the problem that was really generating things for Tom was not the problem of consciousness, but the problem of value. How can you have the experience of some things being better than others, of life being meaningful, of sorrow versus happiness? Of course, that's very deeply connected to consciousness. But I suggested to him that really his hard problem is the problem of value. And he agreed.

He said, yes, thank you. I think maybe that's what's really moving me. It's another famously hard problem. But okay, it's not the hard problem. But they're all mixed up. I mean, you've got to write the best play, right? When I'm an advisor for Hollywood movies about science, the goal is to make the best movie, not to be the best science documentary.

But the play is about to open, actually, here in New York at the Lincoln Center. So I have another round of all of this coming up. Actually, the last, I don't want to give away any spoilers about the play, but at a certain point they mentioned the main character goes to work with a professor at NYU whose ideas are said to be indemonstrable. And various people have asked me whether that's me. I'm actually fairly confident that it's not. I think it's my colleague Tom Nagel.

I think it's Tom Nagel, who wrote, what does it like to be a bat? Yes. And he's the professor at NYU. But simply the label of being a philosopher, whose ideas have been called non-demonstrable doesn't really narrow things down too much. Oh, I was talking about this with my colleague, Ned Block. There's three of us at NYU who work on the philosophy of consciousness,

and we decided that the philosopher in question surely couldn't be either of us because our ideas are demonstrable. Absolutely right. All right, David Chalmers, thanks so much for being on the podcast. Thanks. It's been a pleasure.