Skip to content
All Podcast Episodes

Sean Carroll on Consciousness, Physicalism, and the History of Intellectual Progress

2 December, 2020

  • Important intellectual movements and their merits
  • The evolution of metaphysical and epistemological views over human history
  • Consciousness, free will, and philosophical blunders
  • Lessons for the 21st century


Lucas Perry: Welcome to the Future of Life Institute Podcast. I’m Lucas Perry. Today’s conversation is with Sean Carroll. This episode takes a tour through some of the core intellectual traditions and movements of human history in order to reflect on their strengths, weaknesses, and potential pitfalls. We discuss religion, the Age of Enlightenment, the Greeks, free will, Newtonianism, consciousness, the intersection of the many worlds interpretation of quantum mechanics and utilitarianism, and more. So, this podcast does quite a broad overview of many of the core questions and topics of human life and tries to ascertain where we might stand on solid ground in the 21st century given progress thus far. An unedited video recording of this podcast will be available on the Future of Life Institute Youtube Channel within a few days of the release of this audio only version.

If you find this podcast interesting or valuable, you can subscribe on your preferred podcast platform by searching for The Future of Life. 

Sean Caroll is a theoretical physicist at Caltech. He’s spent most of his career doing research on cosmology, field theory, and gravitation, looking at topics such as dark matter and dark energy, modified gravity, topological defects, extra dimensions, and violations of fundamental symmetries. Recently he has shifted his focus to more foundational questions, both in quantum mechanics, and statistical mechanics, bringing more philosophical dimensions to his work. He is the host of the Mindscape podcast and is also the author of The Big Picture, the Particle at the End of the Universe, and most recently, Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime. 

And with that, let’s get into our conversation with Sean Carroll.

I think there's a lot here for us to get into. So the 21st century is particularly perilous. We stand at the precipice of human extinction, and a lot of this has to do with, I think, taking responsibility as individual persons for the kinds of beliefs that we have. As technology becomes increasingly powerful, the degree to which we require wisdom with which to properly manage it continues to increase.

And there's a lot of bad ideas and people have a lot of trouble with formulating correct beliefs and knowing to use rationality. And what is it that I should believe, and how do I know who the experts are, and this kind of thing. So we have this big problem of information. And what this has brought me to is reflecting on the strengths and weaknesses of Western scientific and rational traditions, as well as wisdom traditions, for example.

So I kind of want to do a tour with you of say, the last few thousand years of epistemology, and metaphysics, and ethical development to comb through to see the strengths and weaknesses of each kind of belief. From religion and mysticism, to science and materialism and physicalism, to quantum mechanics and how they've all interacted and try to leach off of each other in certain ways. So why don't we start here now with going back a few thousand years to perhaps what you might see as the strengths and weaknesses of something like religion or mysticism, given that this is a predominant force in the world still today?

Sean Carroll: Well, I think if we were 2000 years ago, it would have made perfect sense to be religious. We didn't know enough about the world. If you just ask, what is the best explanation for the world you see? We didn't have nearly the resources to provide sensible alternatives to the idea that it was created by some force, some creature, some intelligence greater than our own.

And we more importantly, didn't quite yet have the epistemological tools to figure out how to go about answering these questions. We certainly had empiricism as an idea. Aristotle was pretty much empirical in many of the things that he talked about, but it wasn't entrenched as the right or only way to go about doing things. And certainly Pythagoras, et cetera, would have more rationalist in the old sense of rationalist. The idea that we can just come up with true things about the world by thinking about it carefully, without going out and looking at it. So I don't blame anyone 2500 years ago, or 2000 years ago, who thought the world was enchanted and full of spirits and essences that were pushing things around. But we made progress since then.

Lucas Perry: Yeah. So I see this tension there between the kind of wisdom developed in terms of experiential and life wisdom, with the failure of modeling the world. The modeling of the world is increasingly spooky in that kind of paradigm. Yet there are, for example, bits of experiential wisdom or life wisdom, which are still valid today. And so there's this tension between the epistemology of the inner and the outer world that begins there that I view as science sort of rectifying the failure of the modeling of the outer world as time goes on.

Sean Carroll: Yeah, I'm not sure if it's fair to say that they did better at one thing than the other when you talk about describing the world versus judging it ethically or morally. I agree with you that there are ideas that were put forward in ancient wisdom traditions that we still find wise and useful today. But there are also a lot of ideas that we find horrible and abhorrent. Likewise, for describing the world, there were ideas put forward about describing the world that we still find useful today. Aristotle says, in order to keep something going, you have to keep pushing it, right? And Galileo and so forth, Avicenna, seem to come along and say, well, we don't really need to do that. There's conservation of momentum.

But in the real world, in our everyday lives, your car is not going to go unless you actually put the engine on and actually provide some propulsion. So it was a model of the world that wasn't wholly false. It was just wildly incomplete, and nowhere near able to extend to the regimes that we're now able to extend to with higher technology, better ways of looking at the world. So I would say that both our ability to describe the world scientifically, and our ability to think about ethics and morals in the world, are not entirely disconnected from ancient traditions, but have improved upon them in important ways.

Lucas Perry: Yeah, I totally agree. The epistemology of the inner and outer world, I think have both clearly increased since then, certainly in terms of ethics. So eventually we come to, at least in the West, the age of enlightenment, which features the promotion of reason and the scientific revolution and humanism, which is moral progress that we're beginning to talk about. And atheism as that became more popular in the late 20th century and early 21st century. This is kind of humanism, which is born of enlightenment reasoning. This is also philosophical progress, obviously. And so here there seems to be this epistemological valuing of reason as primary, and language and communication as the methodology by which we come to moral truths and also scientific truths.

Sean Carroll: There's fine distinctions to be drawn here. Like if you, again, told Aristotle or Plato that we need reason to understand the world better, they would've been like, yeah, sure. I don't disagree with that. Now I agree that enlightenment thinkers often portrayed themselves as champions of reason, but it wasn't in opposition to ancient Greek philosophy. It was in opposition to religious dogma, right? And if you talk to the right religious people, they will also say, oh yes, we're all about reason. Religion is a tough thing because there are many people who claim to be part of the same religious traditions, yet have very, very different ways of thinking about it. The whole thing is very messy historically, and I don't claim to be an expert on it. What I'd like to emphasize is this empirical aspect of the enlightenment tradition in the scientific revolution, the fallibility of it.

That's really the key move. And it's kind of interesting and ironic to me, the fact that the major move that made progress epistemologically in the enlightenment was a humble move, right? To say, well, we can't just think our way to the right answer. We need to sort of make guesses, make hypotheses and then go out there and look at the world, and we could be wrong. Whereas, many of the people who are actually doing this are very far away from being humble. That remains true to this day. Personal humility, as far as I can tell, does not correlate with intellectual humility when it comes to understanding the world.

But to me, that was really the most important thing. The idea that you can't just reach your mind out there into the world and come to interesting conclusions about it that are also correct. You can, by all means, come to interesting conclusions about logic and math and pure reason. But the world and how it operates, you need to go and look at it. And that wasn't an easy tradition, right? Plenty of people, from Descartes to Kant, didn't quite fit into that tradition. Even though we think of them as part of the enlightenment and the scientific way of thinking, they were still quite convinced that they could think their way into how things worked. So it's a tough lesson to learn, I think.

Lucas Perry: Yeah. The kind of a priori armchair reasoning of Descartes is quite suspicious.

Sean Carroll: Well, and again, Just to be super duper fair here, there is always an element of that, that you can't get rid of. And Descartes actually kind of, even though he ended up in a weird place, he was an important part of teaching us that with basically the first step of his move to point out that you don't know for sure that you're not being taunted by an evil demon who wants to give you misimpressions about the world.

And I do think you need to do a little bit of a priori thinking just to give yourself the resources to say, okay, I'm going to act as if I'm not a brain in a vat, or being fooled by an evil demon. Or a Boltzmann brain that spontaneously, randomly assemble and things like that. None of those things are hypotheses that you can reject just by collecting new evidence. You actually have to think your way out of them. So there's a give and take between the pure thinking and the looking at the world aspects of this.

Lucas Perry: So for the 21st century, if you were to extract the strengths and wisdom of the age of enlightenment, and you were to promote and more deeply integrate that into the minds of people today, what is it that you would extract and promote?

Sean Carroll: Well, there's so much really. It's like we said, this humility towards thinking about how the world works. And if you want, it's a huge dramatic oversimplification of how things go, but that builds into a Bayesian way of thinking about the world in our modern language, where you say, I have a bunch of things that could be true. I assign credences, degrees of belief, to all the different possibilities I can think of. And then I go collect new information to update my credences and hopefully hone in on the truth. And actually, I think even though I haven't really looked at this super carefully, within the tradition of Bayesian reasoning, or fallibility, or hypothesis testing, we haven't done a good job of explaining what counts as new evidence that we can use to update our beliefs. Sometimes you don't actually have any new data or information.

You just realize that something works in a different way than you thought it did before. And your credences dramatically shift. That's a tricky problem. Is that new information? It's kind of new information, but it's not new data. You haven't collected anything new about the world. But anyway, okay. I think this one idea that we don't know how the world works. We have a bunch of credences for different possible ways it could work. And we go about updating our credences. That's one thing I would take from the growth of the enlightenment

The other would be, even though this actually hasn't caught on nearly as much, some kind of fact-value distinction, right? And again, that's a messy thing and people have argued against it at the margins, and good, fine. But I think that there is some truth to it. The idea that there are things that happen in the world, there are things that the world is made of, and there are ways that it goes. And that's what science teaches us about, the description of the world.

And then there's a whole nother realm of evaluation and norms and judgment and prescription, what is right, what is wrong, right? The is–ought gap. And I'm a big believer in that is–ought gap. And so I think that figuring out how to settle on what we think of as our ideas about right and wrong, good and bad needs to start with that understanding. That it's different than doing science and looking at the world. And it's also different than pure reason. So where do we ground that? I think that's something we're just very bad at today. We haven't made nearly as much progress on that, but it does still grow out of that enlightenment tradition.

Lucas Perry: Yeah. There's this great clip of you butting heads with Sam Harris about his axiom, that the greatest misery for all sentient creatures is a bad thing and you just keep butting your head against him. You're like, well, say it's an axiom. Say it's an axiom, say it's an assumption. I can't restate it, but he uses some other move to try to say that there's no choice to the matter or something.

Sean Carroll: Yeah. I think even though it's a little bit unfair and strawmany to say it, I think it gets the point across if we just sort of say, look, there's a move that is very, very commonly made among people who think that they can find absolutely foundational groundings for morals, which is to pick a particular moral principle and to say, surely you can't disagree with that. And then go from there, and build everything on the top of that. And it's not just Sam who does it. It's a very old tradition. And it's exactly what David Hume was making fun of back in the day.

And it's a difficult conversation to have sometimes because there's a difference between ethics and meta-ethics, right? What is right and wrong versus how do we ground our ideas about what is right and what is wrong? And Sam is saying, well, here's an idea I think is right. And most people are not going to disagree with him. Most people are going to agree. Yes, maximizing misery would be bad, but that's an ethical thing. That's not a meta-ethical thing. You haven't told me in any way why I should believe that or what else I should believe or anything like that. And those are much harder questions.

Lucas Perry: Yeah, that's right. I'm quite sympathetic to Sam's view actually. But I'm glad you bring in the distinction between metaethics and normative ethics, or applied ethics. So from the age of enlightenment, we're extracting this kind of probabilistic Bayesian reasoning. We're extracting this difference between facts and values. This kind of self-awareness about the humility of one's own beliefs and how values are often derived from conditioning and culture. And that there may be some sort of more formal or potentially formalizable metaethical structure, which you implicitly have. You don't even know you have it. And that is sort of upstream of all of your beliefs that you're consciously aware of. And so bringing light to that whole situation is illuminating ethically in terms of your self-awareness as a being in a civilization, and no longer taking anything as absolutely true.

Sean Carroll: Yeah. I think that this idea that we should be more reflective about the origin of our normative commitments, our ethical principles, but also just our more general ways of judging good, bad, beautiful, ugly, right, and wrong and so forth. It's a tough one to do because these things are things about which we have intuitions, right? We have strong feelings. And I would argue that when we turn these into fancy moral philosophies, really what we're doing is just systematizing those intuitions. So yeah, that is the basis on which we're making these judgements. And people don't like that. People don't want to admit that. They all have the intuitions, they admit that, but they want to ground them in some absolutely foundational thing, just like Descartes wanted to do for our knowledge of the external world.

And it just gets very complicated because the external world, I think, really does exist. It's objectively out there. But our knowledge of it does require some leaps. Whereas on the moral or ethical side, there's not even anything out there. We're doing nothing but leaping. And we have to become comfortable with that. And nevertheless, develop ways to talk to each other to reason together, to live in a society where different people can affect each other. And being honest about meta-ethics is a good starting point to that, but a really hard one to get people on the bandwagon for.

Lucas Perry: I'm not sure how I feel about the claim that metaethics is just leaping from intuitions. That would seem to be the case for any kind of intellectual discipline, is that we have intuitions, and that we formalize systems that are either analytic or synthetic based off those intuitions.

Sean Carroll: Well, quantum mechanics does not come about by formalizing our intuitions. It comes about by being forced into it by data, which morality does not.

Lucas Perry: Well, the intuitions are the value of evidence, the value of reason, intuitions about mathematical axioms that are analytically true.

Sean Carroll: Sure. Intuitions play a role. Absolutely. But so does data. So does information we get from the outside world in a way that moral axioms are not fixed by data in the same way,

Lucas Perry: The place where I might disagree with that is the consciousness itself being the data. People who take qualia seriously might say that there's a kind of ineffable, good or bad property to certain experiences. And that that is a kind of data... I think this is the kind of move that Sam might make in that, that is your data. It's not like evolution has just front-loaded us with intuitions that are born of game theory, but rather there is the interaction with consciousness in a way that gives you information about what is good and bad.

Sean Carroll: It doesn't though. It gives you information about what is pleasant or unpleasant. To judge whether it's good or bad is a separate move. Some people like unpleasant sensations.

Lucas Perry: Yeah. So that's going to quickly get into metaethics. So we can maybe loop back around to this. I'm interested in kind of moving through the rest of the history of thought. Though I think this is interesting and fertile ground for conversation. I think it wouldn't be fun if I let you get away from religion and mysticism without talking about any of its advantages that you might see.

Sean Carroll: Oh, I think that there's plenty of advantages. Like I say in my book The Big Picture, it would be crazy to think that for thousands of years, the most rigorous, careful thought about the human condition and what it means to be a good person and so forth was done within these religious traditions. And we end up with nothing useful from that, right? Of course the boundary of what you call a religious tradition is a little slippery, especially when you leave the Western world and go into Eastern ways of thinking. But I'm very, very open to treating all of what has been learned and thought about in these traditions as potential sources of wisdom, just like I'm open to treating fiction and storytelling and biography and good people's lives as potential sources of wisdom also. I think that this is part of the systematization that I talked about.

Moral philosophy is a lot more than just listing our intuitions because our intuitions are mutually incoherent, right? There's no rule that says that our intuitions form some sensible system. That's why things like trolley problems are difficult because we have competing intuitions that push us in different directions. Likewise, when we read or experience something from a religious tradition, it might poke us in a way that we might otherwise not have been poked that makes us reflect. That makes us think, you know what? Yeah, I should have turned the other cheek that time. I should have been able to be a better person, and this experience that I'm reading about helps me in that way.

Now, can I point to very specific examples? I don't know. That's hard for me to point to specific examples because our culture has been embedded in religious traditions for thousands of years. So much so that things that might very well have counted as coming from a religious tradition have now been absorbed by the greater culture. So I'm not enough of a human historian or anthropologist to tell you which ideas came from where.

Lucas Perry: All right, let's pivot here into materialism and Newtonianism, which is born and is relevant to the age of enlightenment. So when I'm talking about materialism here, I'm talking about the universe as being made of substance. It's kind of more Newtonian paradigm, which is not yet quantum physics, but is this kind of substance matter, little tiny stuff that obeys Newtonian mechanics. In the age of enlightenment, at least in Western traditions, there's this increasing duality between man and world. There's this problem solving mindset, which is being applied to what is viewed as the external world. And this is also I think, couched in Abrahamic religions, which have embedded themselves in our language and view of the world where you're kind of visiting the universe. You're here for a short time, and then you die. You leave to go back to the ultimate place. You have a soul.

And so you're visiting this place and this kind of enlightenment thinking is this very dualistic problem-solving experience with relation to the world. And this is emerging alongside an increasingly materialistic view, at least among scientific and intellectual circles, which is like, okay, we're all just stuff and matter. We're basically machines. And so this is overlooking a lot of the introspective and experiential and qualitative aspect of things to some degree. And what's born of this is logical positivism in the early 20th century, which you can talk about perhaps the virtues and vices of that. And reality from this perspective is much more intuitive and mechanical. What is your perspective on this kind of shift in paradigm and this kind of evolution in human intellectual thought as we're getting closer to the present day?

Sean Carroll: I think that it's both important and good in some ways, and you can run too far with it in some other ways, right? It's all in contrast to what was believed before. Before the scientific revolution and the enlightenment, of course you would have associated life and thought with something that is very different than matter in motion, obeying the laws of physics.

Lucas Perry: Élan vital.

Sean Carroll: Yeah. And depending on what tradition you were in, you could have talked about spirit or whatever. Descartes tried his best. Princess Elizabeth of Bohemia tried her best to let him know that he was making some leaps that weren't quite legitimate, but still again, he was a big part of the scientific revolution. Maybe some of the viewers here don't know, I'm a super-duper physicalist about these things. I don't believe there's any special, extra realm for thought or essence or spirit or mind, but I don't choose the word materialist in this sense.

Obviously one reason is there's a whole nother definition of materialist that has to do with how much we like money and things like that. But that's okay. There's also a whole nother definition of the word naturalist that doesn't stop me from using that word. But I do think that when you talk about this Newtonian point of view, this gets at why I think materialist is not a good word to describe what I am. And it wasn't even a good word 400 years ago. It sort of leapt to a conclusion prematurely. The important idea to me, was the idea that there is a physical world, right? There is the natural universe. There's no separate realm of spirits, or essences, or minds. There's just the physical natural world. And then it obeys some rules that we can discover. So there's sort of three pieces to that.

And you could argue about them separately, but they come together to make physicalism, right? There is the physical world, it obeys some rules. And in principle we can discover them. Not easy to discover them, but in principle it's possible. And none of those statements has to do with what the physical world is. The idea that it is objects in space-time, et cetera. Sure, for Isaac Newton or something like that, that would have been a very natural point of view. Nowadays, when we have quantum mechanics and cosmology and a whole bunch of things like that, it's a less natural point of view, but it wasn't necessary even for Newton. It wasn't the point.

So I don't see some great intellectual fissure between the Newtonian way of being a physicalist and the modern way of being a physicalist. Our idea of what the physical stuff is has changed, but physicalism is still going strong, I would say. And then, yes, you can also leap to some premature conclusions about how to think about the relationship between being a person and the universe you're in. Some sort of cleaving of the connection that we have with the wider world. And this is just because people always like to leap to conclusions prematurely. I would actually sort of completely flip it around. Rather than saying that this point of view separates us from the world in some sense, this makes us more part of the world than we ever were. We're made of the same kind of stuff as the world. This should give us more sympathy, more empathy, more connection to the world around us because we're not that special. We're just ordinary stuff doing some extraordinary things.

Lucas Perry: So by materialism, I'm trying to specifically invoke the substance matter of thing rather than the how quantum physics does away with that view where we have this universal wave function.

Sean Carroll:But my point is that, that's not a big distinction. The shift from a Newtonian view where there's space, and there's time, and there's stuff, to a quantum view where there's a wave function and abstract Hilbert space. In my view, that's a very tiny shift. And the kind of shift that might happen again another dozen times in the history of physics in the future as we discover more and more things.

What the physical world is, the specific mathematics or formal system that we use to describe it, is way less important to me than the idea that there is a physical world that obeys rules that we can discover.

Lucas Perry:Yeah. That makes total sense. Physicalism is just like, "There's a world. There's no supernatural stuff and it all obeys the laws of physics." But the sense in which it is relevant is something that we'll touch on a little bit later, is you get this revitalization of certain metaphysical views in spiritual, and religious traditions because it goes from being cold dead matter to being this empty wave vibration stuff that you can make a movie like What the Bleep? about that just totally steals all of the quantum physics and uses it to justify unsubstantiated metaphysical views, for example.

And so, people believe all sorts of wrong things today because of this movement from materialism to quantum mechanics. Most people probably don't believe in pure physicalism because most people are religious and so there is some supernatural component.

Sean Carroll:Can I say something about What the Bleep?, et cetera, before we move on?

Lucas Perry: Yeah, yeah. Go ahead.

Sean Carroll: You're absolutely right obviously, that people have co-opted the language of quantum mechanics to push all sorts of non-physicalist ways of thinking about the world. But that's just a mistake. That's not an interesting move. I blame my own people. I blame physicists for this in a very real sense because we didn't face up to the reality of trying to understand quantum mechanics. Quantum mechanics is different and weird. It's a different kind of physical theory than we had ever had before. It's not just yet another physical theory. It's a different kind of theory and the way it's different is that when we teach quantum mechanics, or when we read about the rules of quantum mechanics in the works of Heisenberg and Bohr, et cetera, the idea of measuring, or looking, or observing at the world is part of the fundamental description of the theory. And given that, it's very sensible that people would leap to all sorts of crazy conclusions about the role of the observer, and the mind, and so forth.

What people haven't yet been told and we're trying to tell them is that, that was something that we talked about 80 years ago but we don't talk about it that much anymore. There are absolutely purely physicalist ways of thinking about quantum mechanics that are 100% in agreement with the data. There are videos out there on YouTube, you can find them, that say, "As we all know, quantum mechanics tells us that idealism was right all along and we create the world by looking at it." And that's very much in the spirit of What the Bleep Do We Know, et cetera.

But those videos are all wrong. They're just mistaken. And so, as physicists, we need to do a better job of pointing out that there's no rupture between physicalism and quantum mechanics.

Lucas Perry: All right. I might put up some defense of non-materialist physicalist idealism some time later. But so, my project here is to, I think, reflect on the strengths and weaknesses of the 21st century mind and how we got here. And so, we've touched on some of the weaknesses of say, spirituality and religion. And I was trying to evoke the weakness in which the human mind can latch on to things that are hard to understand in physics and use it to justify one's own metaphysical views.

So, pivoting back to, we'll call it, physicalism, Newtonian physicalism. I'll stop using the word materialism. So you mentioned how people latch on to things before we know enough to really develop a sophisticated view. One of these we were talking about, the duality between man and world, where we have this world model of ourself as a machine, embedded in the machine and we're not identical to alternate reality itself, which may track back to Abrahamic religions and the kind of worldview that they have.

But there are also other things that I see as this being reflected in how science, and atheism, and physicalism has been promoted and perhaps worked its way through the minds of people in the early 21st century. So there are ideas of free will. A naïve view of free will from this physicalist Newtonian paradigm would be that it doesn't exist. Yet this becomes more nuanced as we get forms of compatibilism. Now that's an upgrade because it rejects the spooky kind of free will?

Sean Carroll: Libertarian.

Lucas Perry: Yeah. Libertarian free will, that's right. So it's an upgrade because it's rejecting Libertarian free will. Yet there's a sense in which, if one takes this naïve view of free will, and one takes a dualistic view of self and world that is born of this physicalist Newtonian view, it leads to a lot of suffering. I'm trying to point out a potential consequence of the experience of a human being in this life given accepting some of these views.

Sean Carroll: Yeah. It's interesting. It's two things pushing in different directions here. One is, I am not going to deny that we might reach certain conclusions about how the world works that make us sad. I mean, it would be the most surprising thing in the world if the progress of science taught us more and more about the world and every single discovery made us happier. The example that I just most obviously use is, I would like there to be life after death. I'm not happy with the idea that I will cease to exist a few decades, or years, or moments hence depending on how things go. But I accept it. I think that it's the right way to think about the world.

The countervailing idea is, people have a very natural predisposition to see the sunny side of whatever worldview they have. So whenever they invent a new worldview, they try to explain why in fact it's better. Right? In fact, it's actually very liberating and so forth. And I feel that. And I want to resist it because I know it's a temptation. It's a cognitive bias to paint your existing situation as what you wanted all along, right? The fox and the grapes. But it might also be true that a new worldview has some positive aspects to it.

So to me, the fact that life exists for a typical human being for a century or less is too bad. I'm not going to say it's better than the alternative. But there are good aspects of it, right? I mean, it makes the moments that we have here in the world more precious, if you think that this is the world that we have. This is the life that we have to experience. It's not just the dress rehearsal for something coming up after the fact.

It's not, in my mind, our place to argue that first, figure out what's true. And then, ex post facto, say, "And that's the best of all possible worlds." But it is our place to say, "Okay, this is true and let's find the good aspects of it."

Lucas Perry: I'm not trying to say in some sense that the truth always has to make us happy. Yet, there's this claim in wisdom traditions, for example, that the truth is ultimately liberating. Or I think some more conventional wisdom is like, "The truth will set you free." That one's a little cringey for some reason to me.

And so, when I was talking about free will, or the Newtonian view, those aren't necessarily true depending on how sophisticated your understanding is of them. But I see this tension here between what you're saying is, "Yes, the truth doesn't have to conform with what we expect or want of reality." Yet at the same time, there seems to be the strength in wisdom traditions, which says, "Even if that's the case and you're suffering now because it doesn't seem to be the way that you wanted it to be, it will ultimately pacify you in some deep sense."

Sean Carroll: Well, I think this actually a very difficult, fascinating thing to think about because I would like to claim... I'm not completely sure this is true but I would like to claim that nobody wants to be misled at the moment. No one wants to actively say, "Please tell me false things that will make me happy." Right? We do that to other people. We decide for them that they'd be better off being misled, right? We keep unpleasant truths from them. But they never ask us to do that.

The one loophole here, that takes me back to a podcast I did with Laurie Paul, who's a philosopher that talks about transformative experiences, really emphasizing the fact that me now is not me sometime in the future. I mean, maybe me now is closely related to me sometime in the future, but the transformative experience idea is that maybe me now is radically different than me in the future. The silly example is, you turn into a vampire and your wants and desires change. But really, the down to earth examples are getting married, having children, going to graduate school, things like that.

And so, I might imagine a dramatic situation in which I choose now to mislead my future self, right? I don't think I would want that. But I can imagine in principle that, that's a possible thing. So, that was basically an elaborate caveat.

But other than that caveat, I think that whether or not the truth sets you free, the truth is something we want, even when we talk these days about fake news, and people who are in their filter bubbles, and believe crazy things, and so forth. None of them, no one, says, "I intentionally only expose myself to fake news so that I can uphold my crazy worldview." They think they're right. People think that they're being accurate. And people want to be accurate. So I don't think it's the truth sets you free, I think it's that we all think that we should have the truth and then we will cope with it whatever way we can.

Lucas Perry: Okay. But I also think that the claim runs deeper than that. I'm not sure that we're going to be able to come up with a reasons and argument here for it. It's more of an experiential hypothesis that I think wisdom traditions propose. But it's not just, you will get what you want by getting the truth because people ultimately want the truth. It's also that you may suffer on your way there because you may have to abandon your identity and abandon how you used to model yourself and the world. But there's not coping afterwards. There is pure pacification. That's a hypothesis and that runs very deep. And you have to embark on the journey to see if that's true.

Sean Carroll: Yeah. And I suspect it's often not true. I mean, I think it's a little bit of wishful thinking going there. But I think it's nevertheless of value to have an accurate view of the world. That would be my hypothesis. Whether or not it sets us free, or makes us happy, or something we can cope with, we want it anyway. I want it anyway.

Lucas Perry: Why do you that, that's not true?

Sean Carroll: I just don't see any necessary relationship between the truth and any positive value that I might have in terms of happiness, or experience, or anything like that. The truth can be depressing. The truth can make you sad. I just don't see any reason why that wouldn't be the case. But I want it anyway.

Lucas Perry: Yeah. I have some intuitive tension understanding what you are saying. And then there's the juxtaposition between pick your favorite awakened historical figure and the kind of experience that they lead. There's this convergence between these examples of human life on this kind of claim.

Sean Carroll: Well, I mean, there is a counter-claim. Owen Flanagan, who's a philosopher at Duke University, points this out to me. He says that when he goes into his class, he says, "Think about the historical figures that have really, for whatever in your personal view have made the world a better place, right? Whether it's Jesus, or Florence Nightingale, or Gandhi, or Martin Luther King. So think about them personally, as human beings. Do you think that they were happy?" He says. Maybe they were or maybe they weren't. But happiness is not the first thing that comes to mind. They were struggling to make the world a better place.

And I think that there is this temptation to say that, "One good thing is every good thing." That good things just go along with each other. And I think it's a little bit more honest to say, "Good things can be in tension with each other. Knowing the truth doesn't make us happier. Making the world a better place isn't easy or fulfilling personally. It might be a great sacrifice." And I think that's okay. And I think that means that we need to make choices and facing up to those choices is part of the human condition.

Lucas Perry: I hear you. So, let's talk about quantum physics. So, quantum physics is continuing this physicalist paradigm. And we already talked about how the bad epistemology of certain religious and spiritual traditions co-opts quantum physics to justify certain claims. And there's now this violation of our intuitions. Whereas before the Newtonian mechanics is in accordance with the human conventional ontology and now it's like, "Well, actually the fundamental ontology is probability distributed and actually fundamentally empty and spacious in the space-time sense of it."

How do you view this shift in relation to the previous shifts and how we should be thinking about and relating to that in the 21st century?

Sean Carroll: Well, I think that quantum mechanics is a more dramatic break from previous physical theories about the fundamental nature of reality. But every theory has some breaks in it. You say that Newtonian mechanics meshes up with our intuition. Well, tell it to students learning Newtonian mechanics for the first time. The idea that without being pushed, things move on a straight line at a constant velocity is highly non-intuitive. We really need to think our way through that and even once you learn the rules, figuring out what a certain thing does on an inclined plane, or whatever, is not necessarily obvious. The distinction between waves and particles, the second law of thermodynamics, and entropy, and probability, and fluctuations, relativity, saying that simultaneity is not an absolute concept. All of these are dramatically at variance with our intuitions.

So that's why I'm saying that quantum mechanics wasn't really different of a kind, it was just different in amount of difference between it and previous ontologies of reality. It was a dramatic difference but it's just one in a long line of differences that might continue toward the future. Not to underplay it.

It's so dramatic that now, more than 90 years later, after putting quantum mechanics together, the experts in the field don't agree on what it says. And that's something that is rare and embarrassing even in the history of physics. We have hundreds of people, thousands of people, thinking at a deep level about this physical theory says and we don't agree on what the theory itself is, much less all of its applications, et cetera.

That wasn't true for Newtonian mechanics, or relativity, or anything like that. So quantum mechanics is really harder than everything else, but it's still physicalism at the end of the day no matter how misused it can be possibly be.

Lucas Perry: There still exists though superstitious and wishful thinking. It's almost as if people don't see that the processes in the world are inexhaustibly explained by the forces of physics. There seems to be this space for something else. And that space is insert your favorite metaphysical view that isn't in science. How would you try to shrink that space or try to improve the epistemology and thinking of people today, given the belief that, that space exists?

Sean Carroll: I mean, it's a very good point and obviously consciousness is the one place where there's plenty of very, very smart people who decline to go all the way to being pure physicalists for various reasons, various arguments, David Chalmers' hard problem, the zombie argument. But other people have various ways of getting to the conclusion that mere physical stuff will never be enough to account for consciousness.

So, here's how I would put it. Number one, physicalism has been incredibly successful at everything else. Right? Even for David Chalmers. You completely buy there's not ghosts and demons out there. That we can explain the universe and what it does in purely physicalist terms. Furthermore, it's very hard to come up with any sensible alternative to thinking of the mind and its manifestations as a physicalist and this goes back to Princess Elizabeth in the interaction problem. If you say there is something that you need in addition to the physical stuff, then you have to face up to the fact that we have a theory describing what the physical stuff does. Given the fact that there are electrons, and protons, and neutrons in your brain, we have physics that says what that stuff is going to do and that includes pushing around your breath and your tongue to make sounds, and make words, and express your inner life, okay?

So if you don't believe that physics is sufficient to account for that, then you need to tell me why our laws of physics are wrong because they make unambiguous predictions. And you're saying if that's not enough, you're saying that those laws are wrong, and so how does this ineffable stuff somehow push around my tongue and my breath to make me say different sounds than I would say if I were in purely physical world?

And finally, I would point out that if physicalism were correct, right? If it were just stuff moving around in complicated ways, what is the thing that would be the hardest to account for? What is the thing that we would account for last in our working through all the difficult things in the world? Well, it would be the human brain because that really is the most complex structure that we know about in the universe. So it is zero surprise that physics as yet, or physicalism even, has not completely accounted for everything that human beings do in terms of their consciousness, and their thought, and things like that. Of course we haven't done that yet. It's hard. That's not evidence that it's not doable. It's just going to take time.

So I would think that there's a huge preponderance of evidence that says, "It's by far the simplest, most reasonable hypothesis that someday we will entirely account for consciousness on the basis of physical stuff. That's not to say we know for sure. We haven't had done it yet. But it's absolutely the way to bet."

Lucas Perry: Yeah. So, this is making me think of your conversation with Philip Goff and I think another aspect of this here is that if someone doesn't have this history of science and the completeness of physics at this current point in time, if something happens and it seems like a miracle or something, that seems to be outside the bounds of the physical theories from that kind of first person experiential point of view. Whereas really the world's a large complex system and unusual things happen every day. And the failure to integrate that perspective with something that seems unique or strange gives credence to these unsubstantiated metaphysical views that then leads to this core epistemology and many other places from politics, to conspiracy theories, and everything else.

So, I really do want to get into the Philip Goff stuff because I think it's really interesting in terms of this tension between the qualitative and quantitative. When you talk about the application of physicalism and the scientific method, because you're saying the human brain, for example, is the most complicated known object in the universe. And we have this first person conscious experience. And you say, you feel confident that because we have this ever-increasing body of scientific knowledge, that this most complex object is the last thing to figure out before the sphere of scientific knowledge encompasses it.

Taking the position of Philip Goff, or I might even put up a bit of a defense of idealism here, that understanding is like fully mapping the neural correlates of consciousness. And you have this view where there's this thought experiment of, Mary is the colorblind scientist who lives in a black and white room and she's never experienced the color red. And so, from a personal consciousness perspective, there's the claim that she's missing some kind of information about what the actual qualitative color of red looks like from the perspective of consciousness. Whereas she could understand the entire neural and causal structure at the level of underlying physics of the wavelength of the light and how that goes in as processed by the brain. David Chalmers refers to that as the easy problems of consciousness.

And so, your view as I understand it is that if you give her the information about the neural correlates of red and then you instantiate in her, that's how you transfer the full information of what redness is.

Sean Carroll: Well, I would try to be more careful about the idea of what redness is and that information. Frank Jackson is the one who originally came up with the argument. And he later said it doesn't work. He himself went back on it. The idea is, Mary's locked in this black and white room. But she reads up on everything that there is to know about the color red. And so there's literally no fact about red that she doesn't know, so goes the argument, except that when she goes outside the room and sees the color red, she now experiences what it is like to see the color red. And she knows something now that she didn't know before, namely what it is like to see the color red. I just think that that's playing around with language in a different way. Yes, it is different to experience seeing the color red than to know a lot of facts in science textbooks about the color red. That does zero work for me to show that human consciousness is not physical. It's a different thing. You experienced red versus learning some facts about it. But I can account for both of those things by physical stuff moving around in your brain. I think that's basically what Jackson himself eventually concluded.

Lucas Perry:To say consciousness is physical is to say that it's governed by the laws of physics. There's a perspective like non-materialist physicalist idealism, which is a big string of jargon. Non materialist means there's not material stuff. It's taking on more of the perspective of quantum mechanics. It's physicalist by saying that consciousness is purely described by the laws of physics. There's a sense in which the laws of physics inexhaustibly describe the world. There's really not much room for, say, consciousness, for example, to have causal efficacy, because then you would wonder, well, there's some variable in the equation that's missing. But there's still the metaphysical question, which is more like the hard problem, which is why do these neural correlates, or why does this causal structure, give rise to the qualitative experience of red, which is distinct from the quantitative theory.

Sean Carroll: Yeah. And so this is where I would try to explain things in terms of different vocabularies for talking about the world. Different levels of description. I would certainly never say that consciousness has no causal efficacy in the world. Me being conscious of something might very well affect how I act about it. What I would say is, if I'm trying to explain how I behave in the world, in terms of my beliefs, my conscious experiences, my reactions to them, my desires, et cetera, that's just a different way of talking about the world than explaining the world in terms of electrons, and protons, and neutrons, and the laws of physics. And those two ways must ultimately be compatible. But I can use either one of them independently. But they're over-complete in a sense. I don't need to tell you what all the electrons and protons and neutrons are doing, and to tell you about consciousness and beliefs and predispositions. I can use either vocabulary perfectly well.

There's no incompatibility in my mind at all to saying that consciousness is real. We have thoughts. We have experiences. We have ideas about what it is like to see the color red, et cetera. And we're a big wave function in Hilbert space evolving according to the Schrodinger equation. Those aren't two things that are in competition with each other. Those are just two different vocabularies to describe the same situation.

Lucas Perry: The thing here that seems to be maybe escaping me is around the metaphysical status. In the non-materialist, physicalist idealism, the solution to why there is consciousness is because the ground of being to physicalism is consciousness itself. Human beings are identical to fundamental reality and reality privately within the inside is aware, and has a qualitative nature to it, which seems to be in tension with the quantitative descriptions that we can give about the causal structure that underlies the qualitative aspects. It seems to be of a different kind. And so there's this question about the metaphysical status, which seems not to be answered by, say, quantum physics or whatever else.

Sean Carroll: Certainly not by quantum physics. I don't think that quantum physics has anything necessarily to do with it. But I just don't think that idealism survives confrontation with the real world very effectively. you start with the idea that mind or consciousness is fundamental. The huge barrier to pushing that forward is the fact that the external non-conscious world seems to be objectively real, and highly complex, and independent of our mind. We human beings experience the world and there are aspects of it we wouldn't have guessed. And we learn about them, and they're the same for all of us. So at the very least, you have to say, in addition to minds and consciousness, there is some physical objective outside of consciousness -- reality that is able to be experienced by us. And then you realize that if you believe in that you don't need to believe in the minds and consciousness as being special. They can just be aspects of that physical reality.

I don't think that the idea that we have internal conscious experiences therefore, somehow, by some chain of logic, we need to include that as a category in our ontology, just doesn't seem to have much purchase for me.

Lucas Perry: I think that the non-materialist physicalist view, though, is that there is fundamental reality, but the ground of that reality is all mind. You're saying that there's an external reality outside of mind, but the view is actually that the ground of that is just more mind. It's isomorphic to physicalism and the laws of physics. The mind is inexhaustibly described by physics.

Sean Carroll: It just seems to be wildly unhelpful to do that. If I can just say there's a physical world and it obeys these laws, what am I gaining by saying, there is a notion of mind... Not an actual mind in someone's brain, right? But some much more ineffable, metaphysical thing, mindy-ness that contains all of that physical reality. It seems to be entirely backwards in terms of explanatory elegance, in my view.

Lucas Perry: The place that I see that is helpful is it explains why I, for example, being identical to fundamental reality, I'm having an experience. Could you explain like what your perspective then is on consciousness, and how it arises, and what its ontological or metaphysical relationship is?

Sean Carroll: I think that at the level of our vocabulary, if we're talking about human beings, consciousness is an extraordinarily useful idea, extraordinarily useful category. The thought experiment of being alien, and coming down and observing human beings. And you see them talk to each other, you hear them saying, Oh, I'm sad. I'm happy about this. I saw red yesterday. In the theory that you would develop for what a human being is, you would invent all sorts of internal states. And you would eventually come up with some word for all of these different feelings and experiences that these human beings had. And that word might be consciousness. Of course, you can't get through the day thinking about human beings without attributing consciousness to them. But that has nothing to do with whether or not that consciousness is explicable in terms of physical terms or not.

There's plenty of other categories that we use that are higher level intrinsically and yet are perfectly compatible with underlying physicalism. Here's how far I would go. I think that the idea of zombies, which Chalmers introduced, which he says, imagine that there are physical things that are atom for atom copies of us, that act in exactly the same way as us, but don't have internal experience. Are not conscious. And he says, just because I can conceive of that, if I can, then clearly consciousness has to be something in addition to the physical stuff, because as I said, the physical stuff is exactly the same, but it doesn't have consciousness.

But look, my attitude is this is a wonderful argument in favor of physicalism.

Lucas Perry: Yeah, let's hear it.

Sean Carroll: Because I talked to the zombie. I had a zombie. You promised me this person is a zombie. They are physically acting exactly like a human being would. But they have no internal consciousness. So I ask them about their internal consciousness. I ask them about seeing the color red, feeling pain, all of these things. They give me exactly the same answers that a human being would. That's the point. They act exactly the same. But I know, somehow, God told me, that they don't really have any internal experiences. Therefore, they're wrong. They think that they have internal experiences. Otherwise they wouldn't be lying to me. But they're completely wrong about having those internal experiences. Therefore, the conclusion is the introspection of the zombies is completely unreliable. They do their best to think. They're like, yeah, I saw that red. It was very vivid. It really made me angry. Just like a human being would, but they're completely wrong about that. Therefore, I have zero reason to think that human beings are any more accurate when they introspect and tell me that they have internal conscious states.

Their feelings about them are exactly the same as a zombie would have. And therefore the only argument against physicalism is completely undermined by the idea that there could be zombies.

Lucas Perry: Those worlds are indistinguishable because there's no epistemic tool for saying whether or not you're actually conscious. Because they're causally isomorphic, so you wouldn't know whether or not you were in the conscious world or the unconscious world.

Sean Carroll: It's basically that, but it's a tiny bit stronger than that. The only evidence that you have that there is something called consciousness over and above the physical world, you've just argued is completely unbelievable. It's completely unreliable. So, there's zero evidence. If you think that there can be zombies that tell you all about their inner experiences, but don't have it, then you must believe that the connection between inner experiences and what you say about them, what you report about them, what you think about them, is entirely, a hundred percent unreliable.

Lucas Perry: Because the report is the same in both cases.

Sean Carroll: Right.

Lucas Perry: Yeah. I think that's a really good objection actually. But if there's an isomorphism between red and the neural correlates that structure and are related to red, then the brain could be pointing towards that neural architecture. And the experience could be pointing towards that qualia. And there would still be an isomorphism there. And so that's how you would be able to communicate about it in non-physical materialist idealism. Does that make sense?

Sean Carroll: I'm not sure that it does. Those neural correlates would also exist in the zombie. You're just adding a completely inefficacious, extra category to your ontology for no good reason.

Lucas Perry: Can you tell me why this isn't anti realism?

Sean Carroll: Consciousness exists. It's real. I talk about it all the time. I asked this question to people like Sam Harris, who don't believe in free will. Have you never tried to make a difficult decision? Do you really just say, well, let the laws of physics do what they're going to do? Of course. At the level where we talk about people, we attribute choices and volition to them like we attribute conscious experiences to them. And I'm all in favor of that. I think that they exist. They're real. They should be treated as such. That doesn't provide any evidence at all that they are not isomorphic to physical things going on in the universe.

Lucas Perry: So your perspective is that we have this kind of conventional ontology, which is a fabricated layer, which we impose upon reality. It is consisted of tables and chairs and people and free will and consciousness and clouds and galaxies and stuff. That's this layer of understanding. And you talk about there being layers. You have chemistry and biology and physics and quantum physics. And that they map to each other in some way. They're not incompatible because there is this relationship between them that is concrete.

Sean Carroll: And even more than that, there's nothing fabricated about them. Tables and chairs really do exist. There's a difference between explaining things and explaining them away. The chair doesn't stop existing when I realize it's made of atoms.

Lucas Perry: I think the distinction here, and this is relevant to consciousness, which we'll get into in a second, is, for example, you're not a fan of Sam's take on free will, free will being an illusion. What Sam is arguing against, in my understanding, is he's arguing against libertarian free will, which I'm sure you wouldn't agree with, right?

Sean Carroll: I do not agree with libertarian free will. Yes, that's right.

Lucas Perry: Within the folk ontology or the folk experience of a human being, we experience ourselves as having libertarian free will. When we're deciding whether to pick up my wallet or my phone, it feels like libertarian free will. And Sam's coming along, and he's like, keep doing that because that's the difference between living a life as fatalism as you described it, saying, Oh, I'm just going to let the laws of physics take over. But that's an error because this libertarian experience is still couched and run on the fundamental physics. It's isomorphic to it. And it's how agents make decisions. What Sam is saying is, do that, but realize that it's a kind of fabrication. That ultimately you're identical to the laws. And quantum physics is governing the whole thing, but you're going to have this fabricated experience on top that is not actually the thing. And so it's conventional.

Sean Carroll: I just think that all of these words, like fabrication and error and illusion, are completely misplaced in this context. The higher level emergent patterns are incredibly real. They're there. They didn't have to be there. You could imagine alternative laws of physics where the higher level immersion patterns just aren't there at all or just take on very, very different forms. To say that tables and chairs exist is a true, interesting, non-trivial fact about the world, just as saying that free will and consciousness exists is a true, interesting, non-trivial fact about the world. And we'd be dopey not to recognize it.

Lucas Perry: Right. But there's this sense that human beings experience the table as a platonic thing. When people say the table doesn't exist as a table, they're saying, don't look at the table as a platonic thing. The table is a pattern, right?

Sean Carroll: Yeah. When you say people in their everyday lives imagine they have libertarian free will, I don't know. I don't really necessarily care. They imagine they're making choices. That's all I care about.

Lucas Perry: Yeah, we do imagine that.

Sean Carroll: Whether or not they imagine that they have the ability to violate the laws of physics while making those choices, I don't think that that's actually part of their decision-making process. I think that that's like setting up a straw man to knock down. They're making choices and that's what matters.

Lucas Perry: Yeah. And I that's the way I use the word free will. But consciousness seems of a different kind because it's not in the ontology.

Sean Carroll: To me, it'd be very... Forget about very weird. It would be impossible to talk about the human scale world if you literally removed from your vocabulary any idea that human beings had free will or that human beings were conscious. That's the evidence that these things are real. They play an important, non-trivial, non-extricable role in our best way of talking about the world at that level. When I was talking with Sam about it, he kept coming back to this point, which people often come back to. If you were Laplace's demon, if you knew the exact positions of every atom in your body, and you knew what was going to happen next, then you wouldn't have free will. Yeah, sure. That's completely true. But you're not Laplace's demon and you will never be. If you were Laplace's demon, you wouldn't need to talk about tables and chairs either. But we're not. We literally cannot be. We don't have the capacity to do that. Let's face up to the limited view of the world that we have. And within that view, the vocabulary of being conscious and making choices is both very important.

Lucas Perry: But again, there's the tension between being a physicalist and knowing that your choices are basically just physics running and the experience of that being libertarian. And so Sam's like, it's not libertarian it's physicalism. And you're like, Oh, well that's not my experience of the world. Similarly, it's like, yeah, there are tables and chairs, which are patterns of physical phenomena. But they're not platonic independent entities that are fundamentally different from you.

Sean Carroll: I think there's two things that I could say to that. One is, I just don't think that most people, when they go through the world making decisions, are really wedded to the idea that those decisions are independent of the laws of physics. I think they just don't think about that. They just don't care. They just make decisions. And the second thing is, if you really wanted to insist that people make a choice about whether or not their decisions were compatible with the laws of physics or not, and only that would count as free will, go nuts. Be my guest. Whatever words you want to use to describe it, I'm still going to think about people's making choices. That's what matters to me. Not whether it's libertarian or not.

Lucas Perry: What does it mean for something to be real for you? And what do you mean when you say that consciousness is real?

Sean Carroll: It's part of an algorithmically compressed description of the world that gives us insight into what happens, what the world is doing, and what happens about it? When we talk about, well, how will this person react to the following news I will give them? The idea that it will make them sad, or it will make them happy, is important. I think that abandoning those ideas would give us a worse description of the world rather than a better one.

Lucas Perry: Are fundamental forces of nature algorithmically compressed descriptions?

Sean Carroll: Yeah, sure.

Lucas Perry: Okay. Is space-time an algorithmically compressed description.

Sean Carroll: Yep.

Lucas Perry: So, in this view, all phenomena that we can define and name are algorithmically, compressed descriptions.

Sean Carroll: Well, in my view, there's something called the world. There's reality. I don't know what it is. I have guesses as to what it might be. But I model it. I pick out aspects of it, and I describe them, and I talk about their relationship, and where they might go in the future, maybe definitively, or maybe just probabilistically. And I can do that at various levels of resolution. And it's useful to me.

My favorite example is just the motion of the earth around the sun. Given the mass of the sun, and given the mass of the earth, and their velocities, all I need to tell you is the center of mass location of the earth and the sun to tell you how the earth will move. I don't need to tell you the location of every atom in the earth. That is information I don't need. I have a highly compressed description of that. Now, you can say, well, the center of mass of the earth isn't real. The only thing that's real is all the atoms it's made out of. Bless your heart, go ahead and do that. I'm still going to use this way more efficient description. It gives me real insight about the world that is a non-trivial feature of the laws of nature. And I can say all of those things about people making choices and people having experiences.

Lucas Perry: Is the description complete though, when it doesn't include, for example, laws and principles that are included in quantum mechanics?

Sean Carroll: No, of course it's not complete. Until we have the once and for all final theory of everything, all of our ways of talking about the world will be incomplete. That doesn't mean that they're not right or useful.

Lucas Perry: Right. I think there's this difference between truth and useful. That theory is approximate. But if it doesn't take into account things that happen in quantum mechanics that might subvert that model, then it's accurate but not true.

Sean Carroll: Then we're just talking about definitions. And that's a definition of true, but it's a definition of true under which we will never in the future of all history ever be able to say anything is true. Because we can never know for sure that there's not a hidden description underneath that doesn't require a lot more information that we don't have. So you're welcome to that definition. I just don't think it's a very useful one.

Lucas Perry: This makes me think of Anthony Aguirre, who talks about reality as fundamentally being information. You're talking here about what counts as real as being this algorithmic compressibility of levels of reality. And it leaves me confused about the metaphysical status of certain things. People want is this thing true as a third person, objective fact. And this participating in modeling the world by saying, can I algorithmically compress this thing? It's bringing out that we can't escape the fact that we have to do that. My reaction is, okay Sean, was consciousness there at the very beginning. Is it part of the fire and the equations of physics? Why is it here to begin with?

Sean Carroll: I think that Daniel Dennett has a good way of thinking about this in terms of what he calls real patterns. And the word real is doing a lot of work there. And it's the fact that we have these very, very compressed, useful, but not a hundred percent accurate ways of talking about the world. Again is a highly non-trivial fact about the world. Take, again, the earth moving around the sun. When you construct the center of mass of the earth, you take the locations and the masses of every particle, and you average them. And then you get one number. You're throwing away an enormous amount of information. All the relative positions of all these different particles. And that tiny bit of information you're left with is still incredibly useful. It tells you where the earth is going to go.

Whereas if you chose almost any other way of throwing away that much information, let's say instead of the positions you average the positions of half of the atoms and the momenta of the other half, you would get a number that would be completely useless. It would be completely non-predictive. It wouldn't tell you anything about the world. It has nothing to do with our human convenience. There is a real, physical fact about the world that you can approximately model it using this incredibly tiny amount of the data that in principle you would absolutely need. Is consciousness there at the beginning of the world? No, but the possibility of consciousness existing was always there. If I tell you someone is sad, that just doesn't convey the word sad. It conveys to you a whole bunch of information that you instantly know. That's why it's a useful feature, useful real character of the world.

Lucas Perry: There's quantum physics, and there's Newtonian physics. And Newtonian physics abstracts away certain things, but it's still accurate. You just gave this example of the earth rotating around the sun, and the center of mass there. There's a similar analogy between quantum physics and Newtonian physics. You're saying, for example, Newtonian physics is real in the Dennett sense because it's the strong pattern feature of reality. It's non-trivial. That Newtonian physics works.

Sean Carroll: Didn't have to be that way. That's right. Capture something real. The joke that I sometimes tell is, if you go on a date with someone, your first date, and they say, tell me about yourself. Do you give them a list of all your atoms and their positions and velocities? You could do that. But not only is it impractical because you don't know it, it actually is not useful. What would you do with that? Whereas if you tell them your age and your occupation, your interests, by giving them much less information, you've told them a lot more. Because you're giving them a handle on who you are at this emergent higher level where we're human beings with interest and occupations and things like that.

Lucas Perry: I think the reason why I'm getting confused is because Newtonian mechanics doesn't have a fundamental metaphysical status. If we have a theory of everything it's not included in that theory. It's actually derived from it in some sense, right? Similarly, if consciousness as a kind of metaphysical part of the world the way in which gravity and electromagnetism and these kinds of things are part of the fundamental theory is. It's spooky and weird to say that it just arises later in the same sense that Newtonian mechanics does. Because we're saying here, Newtonian mechanics isn't fundamental, it's actually just a derivable thing. Consciousness isn't a derivable thing from patterned phenomena later. It seems more to be a core essential primitive thing. There's no way that it's not primitive.

Sean Carroll: No, I think that there's a big way that's not primitive.

Lucas Perry: A minute. Okay. I think that's why there's this confusion between, say, you and Philip Goff and people who take idealism and panpsychism seriously.

Sean Carroll: Yeah and I don't think it's a close call or a fair fight. I know that I made of all these atoms and they're all obeying the laws of physics. There's no room in there for anything else.

Lucas Perry: But then, why are you conscious?

Sean Carroll: That's an emergent pattern at the higher level.

Lucas Perry: Why?

Sean Carroll: Well, the laws of physics allow for that and the specific arrangement of the physical world instantiates it.

Lucas Perry: But it sounds like you're just talking about the easy problem and not the hard problem.

Sean Carroll: I think the hard problem just evaporates. I think that there's not going to be some brilliant philosopher or neuroscientist 20 years from now who's going to say, I've made a discovery and I now understand the hard problem. I think, as we understand more and more about how the brain works and how it gives rise to human beings talking about and feeling their experiences, it'll just stop being interesting.

Lucas Perry: Sorry. That's only funny because it's very interesting to me. And I don't see it becoming not interesting. I think wrapping up here. So you think that the hard problem will go away or become uninteresting. And then my position is more like, it seems primitive. And there's this sharp distinction between the qualitative and quantitative. And the qualitative almost being an innate capacity at the beginning. And where the fundamental forces in this physicalism is only describing the quantitative. And then I'm saying, well, there's this capacity for this purely qualitative thing from the start that seems primitive that I would like to have included in the fundamental metaphysics. And you're saying that it's actually an emergent phenomenon like Newtonian physics is a phenomenon. It's part of our folk ontology. It's part of our folk way of describing the world. It compresses a lot of information that is very useful in the same way that when we talk about free will, it compresses information in a way that is useful. Yet the hard problem is still compelling to me.

Sean Carroll: I agree with everything you just said. Just to point out. The idea that certain problems seem incredibly pressing and then don't get solved but kind of evaporate away because our perspective change and we realized they weren't that pressing after all happens all the time in science. Back in the days of Kepler and Copernicus, why are there five other planets other than the earth. Mercury, Venus, Mars, Jupiter, Saturn. That was a incredibly pressing question, and they came up with all sorts of elaborate schemes to do it. Just a hundred years ago, why is the fine structure constant one over 137? Arthur Eddington, you know, worked very, very hard at understanding this. And now we know these are just not interesting questions. It's not exactly 137. There's not five planets. We change our perspective on what questions are important and what are not.

Lucas Perry: So do you use a bit of jargon, that's nomological, right? I actually think that those are really good questions and I think there are hard problems of constants. And so if you want a full theory, then ultimate reality has chosen those constants. Why?

Sean Carroll: Yeah, sure. It's not an exact analogy, but my point is just that what might drive research and intellectual inquiry forward in terms of questions we're trying to answer might change not because we answer the questions but because our idea of what is an important question might change. What are the sets of questions that would give us true insight to answer? If you told Kepler, well, the reasons why there's five other planets is because we're one solar system. There's many, many different solar systems that have different numbers of planets. In fact, there aren't just five planets. There's other planets you haven't seen. It's just an accident of where we happen to be in the world. It's not something that is fundamental in and of itself. He would not have considered that a good answer to his question. But we now know that's the right one.

Lucas Perry: Okay. I've really loved this so far. And something feels unsatisfied. You might feel unsatisfied with how I view the hard problem as being serious. And I feel unsatisfied in terms of you kind of explaining. It seems almost anti realist.

Sean Carroll: Well, I mean, I do get it. I tried in the big picture to put forward a dialogue between someone who really took the hard problem seriously and someone who didn't. I had David Chalmers on the podcast and I tried to press him on this. And I said, well, a zombie would think they're conscious. By definition, that's what they would tell you. And so how do you know you are conscious? How do you know you're not a zombie? And he's like, I just know that experience it. It's part of who I am. What can I tell you? And you hit a point where further discussion is not going to be very helpful.

Lucas Perry: Okay. I think that's a good place to end there on that. You do hit a place. And I'm in the Chalmers camp. I'm just like, I know. This is the thing that I know first. I take the Descartes line of view. I'm like, this is more certain than the external world. And we're actually coming back to consciousness after assuming the external world to make the kinds of arguments that you make. And so the external world is actually a kind of inference. Whereas the reality of consciousness is more like prima facie true. It's quite interesting and difficult philosophical ground. And I am also aware of how it almost feels like ramming your head against a wall when people are talking about this with different perspectives.

Sean Carroll: Yep. I think that's completely right. I have nothing to disagree with about there.

Lucas Perry: All right. So I want to hit you with a fun one here. I think it was on the Joe Rogan podcast. You said the good thing about the multiple worlds interpretation is it doesn't really change how you should live your life. Now, in the effective altruism community and some quiet, avant-garde philosophical thinking, there's a realm of infinite ethics. It's about how utilitarians deal with the multiple worlds interpretation of quantum mechanics. And so the question from the audience here, specifically someone from the Qualia Research Institute who takes consciousnesses as kind of metaphysically fundamental is, is the number of moments of experience larger in the future due to the repeated bifurcation of the universal wave function? Should we care more about what happens in the future because there are more copies of it? At the Future of Life Institute, we work on trying to reduce and mitigate existential risks. So does this sort of increase the priority of existential risk by meaning that the future is more valuable than the past?

Sean Carroll: So, I think the first thing I should say is, I'm not a utilitarian. And thought experiments like this are part of why I'm not a utilitarian. I think that utilitarianism seems perfectly reasonable when you face up to it. But then when you think about what it means, it kind of falls apart in a whole bunch of ways. Having said that, I think that even utilitarians should not be overly concerned with the wave function of the universe. Or at least let me say the following. I think that as a metaethical principle, as I said before, I think that moral philosophy comes from trying to systematize and make rational and coherent our intuitions.

So if you have a view of what utilitarianism means in the many worlds interpretation of quantum mechanics, and then you realize it completely violates your intuitions, then I think that you have the right to back up and fix your utilitarian guess as to how to apply that to many worlds. So if you are a super naive utilitarian who counted utility by just adding up the utility in all branches of the wave function, then clearly the best way to be a good person is just to duplicate the universe over and over again. To go into your basement and make quantum measurements so you make lots of different universes, however that's possible. And that literally affects nobody in the world. No one's life is changed by you in your basement measuring a bunch of spins of atoms and therefore branching the wave function of the universe.

So I would say, you need to back up and fix your utilitarian calculus. And the obvious way to do it is to say that not all universes are created equal just as we assign a probability measure to the outcomes of experiments in many worlds. We say that, okay, if a certain spin is square root of two thirds, spin up plus square root of one thirds, spin down. What I'm going to say, the words I'm going to use are, there's a two thirds probability I will observe spin up and a one-third probability I observe spin down. And a non Everettian would say, that's crazy pants. There's a hundred percent probability that one version of you will see spin up and one version of you will see spin down. Where does this two thirds and one third come from? And the answer is everything in a sensible Everettian many worlds view of the world needs to be weighted by the wave function squared. That's the thing that gives you probabilities. That the thing that adds to one that's conserved over time. Why doesn't it violate energy conservation to make new worlds? Because you need to multiply by the wave function squared.

So I would argue that the same exact thing is true for utility if you're a utilitarian. I'm not a utilitarian. But if you want to be a sensible non-crazy utilitarian in many worlds, you have to count utility as being proportional to the thickness or the weight of the individual worlds. You can't just double the utility when you branch the wave function of the universe. And in that case, going into your basement and splitting the wave function of the universe by measuring a bunch of spins has exactly zero effect on the utility of the universe. And so that is why I conclude that the right way to behave in many worlds is exactly the same way as you would behave, whatever that is, if you thought that quantum measurements were truly probabilistic, truly stochastic, obeying the rule that the probability is just the wave function squared.

Lucas Perry: Sorry. Maybe I missed part of the argument here. I think I've heard you say that we're unsure if everything happens somewhere or if just some very large fraction happens.

Sean Carroll: Well, it's not that we're unsure. Certain things will never happen.

Lucas Perry: Like things which are contradictory?

Sean Carroll: Well, there's things that contradict the Schrödinger equation, like charge conservation will not be violated. There's some Schrodinger equation that evolves the wave function forward. And that does not imply that everything happens, it implies that the Schrodinger equation makes certain predictions for what's going to happen.

Lucas Perry: Okay. And so when you're branching the universe, are you not duplicating the value or disvalue that is here?

Sean Carroll: You're not. That's the crucial point. Let's imagine that you are not an Everettian. Let's imagine that you thought that quantum measurements were truly random, were truly stochastic. If you measure a spin that is in a wave function square root of two thirds spin up, square root of two thirds spin down. And you just do that over and over again. There's only one world we're imagining. But two-thirds of the time it'll be spin up in one third of the time, it'll be spin down.

So, I would argue that a sensible utilitarian in that case, what are they going to try to maximize? They'll maximize the expectation value of the utility. If you think that spin up has a certain utility and spin down has a certain utility, but you don't know because it's stochastic, you should try to maximize the expected value of that utility.

So my point is you should do exactly the same thing in many worlds. You don't just add the utilities of different branches, you take their expectation value and you weight them by two thirds or one third. The expected value of utility is the same whether or not the world is fundamentally stochastic or whether or not there are many worlds. You're calculate in the same thing. There's no difference to what you would predict.

Lucas Perry: I'm sorry. Why isn't that clear to me? Is it because of how the math works out?

Sean Carroll: I'm not sure why it's not clear, but if you're an Everettian and you say that, okay, I had this spin, square of two third spin up, Square root of one third spin down and I measure it. Now, I say, okay, now there are two worlds, one in which it was spin up one in which it was spin down. But then each world has an amplitude. It's not just that there are two worlds. One world is square root of two thirds times this world and the other world is square root of one third times that world. And whether it's energy or utility, you should take the expected value by squaring those amplitudes and multiplying that by the value in that world and then adding together. Which is exactly what you do if the world is fundamentally stochastic. It's the same process.

Lucas Perry: Oh, I see what you're saying. That makes sense now. I wouldn't be able to say it back to you. I'm mathematically naive, but it makes sense.

Sean Carroll: Good.

Lucas Perry: All right. So I'm mindful of the time here. And I would like to do a full circle here with you of being a thoughtful, scientifically and philosophically informed person in the 21st century. One thing that I really appreciate is how eclectic your knowledge is. I think you've mentioned how sometimes physicists or cosmologists can be philosophically naive. I really appreciate that point and the kind of depth and breadth that you bring to all fields of inquiry from ethics to science, to philosophy. So in the spirit of having that kind of depth and breadth, which seems increasingly important in the 21st century because the world's only getting more complicated. And so it's demanding more and more wisdom and knowledge from the people which inhabit it. What would be your message and suggestions and takeaways for humans of the 21st century?

Sean Carroll: Yeah. That's hard to answer because I have nothing much more interesting to say than a bunch of cliches. Of course it's important and interesting to learn lots of different things about lots of different fields. But I guess the non-trivial thing I would say is let's put it this way. Some version of the principle of charity is what I would advise people to do.

There's this famous/infamous example recently in the pandemic where Tyler Callan who was a former podcast guest also wrote a blog post. He's an economist. And he wrote a blog post that was pretty insulting towards epidemiologists. They're not as smart as we economists are. They have a lot to learn from us. And on the one hand, maybe they do have a lot to learn. That's completely possible to me. On the other hand, I think that you could do a lot better job when you enter a new field... And by the way, physicist do the same thing. There's also famous examples of physicists saying, well, we'll model epidemiology in our spare time because we're physicists, it's easy for us. Taking the difficulties of other fields seriously is very, very hard. And asking what questions, why they think the questions are important that they do, why they made the choices they made, et cetera. It's very, very hard because it's not that different people coming from different perspectives don't have anything to offer.

I think that physicists and economists and whoever might have a lot to offer epidemiology. But the first impulse should be to be humble, to say like, I'm new here. Explain to me what's going on. Let me learn. Rather than to come in and say, let me tell you how it is because I have this superior training and I can figure things out. I think that usually people from different fields are not smarter than the people of the fields that they're trying to learn about and talk to. So by all means be intellectually curious and wander into other fields, even make suggestions to them, but be reasonably humble while doing it. That would be my idea.

Lucas Perry: You meant epistemic charity, not like moral charity.

Sean Carroll: No, that's also important too. But yeah, I'm thinking about epistemic charity. Try to think about what other people are saying in the best possible light that you can imagine.

Lucas Perry: Yeah, taking people on good faith. Sam Harris was on our podcast and he talks about how conversation is so important. It's the only way which we have to arrive at truth with other people. And there's a sense in which taking people on good faith, which is a kind of epistemic charity is essential and crucial to that process, but is deeply lacking in our discourse.

Sean Carroll: Well, it is. But just to make things harder, there are people who are not talking in good faith. So I think your first guess, your first move should be to take people in good faith and try to see how far that goes. And at some point you can just shake your head and go, no, sorry. You're not playing along.

Lucas Perry: Yeah. So I guess just as a rapid fire question here, it's just coming up in the philosophy of mind. Do you have a formal position? If you were just to say what it was in terms of the jargon. What is it?

Sean Carroll: No, I don't trust my knowledge of the jargon well enough give anything. Obviously I'm a physicalist. I'm a compatiblist when it comes to free will. Details about how the mind works are above my pay grade.

Lucas Perry: Sorry. I meant philosophy of consciousness.

Sean Carroll: Oh. Well, what choices are you going to give me there?

Lucas Perry: Like idealism and panpsychism and emergentism.

Sean Carroll: Yeah. I'm a physicalist. I am an emergentist in my own vocabulary, but I know that in other people's minds, that word means something else. So I don't call myself that among philosophers.

Lucas Perry: Okay. That still leaves me a little bit confused because the views in this tradition of philosophy of consciousness give different epistemic credences. So idealism says reality is ultimately made of consciousness. Panpsychism says that there's fundamental physical stuff, yet it also has a mental property to it along with the physical properties. And then emergentism says that you get all this stuff that comes together. And then like Newtonian physics emerges from quantum physics, consciousness emerges from quantum physics or the interaction of physical stuff.

Sean Carroll: Right. And so I use the word emergence a billion times in The Big Picture. Like I said, I would describe myself that way. But there is a tradition of emergentism which says that there are things that exist at the emergent levels which even in principle cannot be traced down to a more fundamental view of the world. That principle is important to me. So the dichotomy that is set up is sometimes reductionism versus anti reductionism. But I don't think that's the right dichotomy either. I'm actually writing a paper that I call figurative reductionism, because I do think that there are levels of description that have different domains of applicability in different amounts of comprehensiveness when describing the world. But I don't think that the more comprehensive descriptions are necessarily descriptions of smaller pieces of nature that fit into some naively reductionistic formulas. It's a little bit more subtle than that. The only word that I'm a hundred percent comfortable giving myself in these discussions is physicalist.

Lucas Perry: Okay. That's wonderful. I bashed my head against the wall I think three to five times having people explain to me why reductionism isn't true. You just talked about how there are emergent things which cannot be reduced to ultimate laws. That's to me, I still don't understand it. And I'll need someone else to sit down with me for five hours to explain why that's true. I keep having people tell me that reductionism is not true. And that to me is amazing.

Sean Carroll: It might just be vague. It might not be your fault.

Lucas Perry: Yeah. All right. And so as a very last question, do you also have then a formal meaethical view? You talk about how it's a systemization of intuitions. Yet a lot of meta ethics, like for example, error theory says that all moral statements are false and then there's moral realism which says some are false and some are true. What is your perspective then on metaethics?

Sean Carroll: Yeah. They're I do map on more cleanly to a well-known point of view, which is Humean constructivism. So not quite a relativist, because relativists will say that morals are relative to some society or culture or whatever. But I'm not an objectivist or realist either. I don't think that morals are out there to be discovered. I think that we construct them. We make them. So the difference between Humean constructivism and Kantian constructivism is the idea that there might be one right way to construct them would be a content point of view. And the human point of view is there might be more than one way that you could sensibly construct moral truths.

But the difference between a constructivist and a relativist is that a constructivist has no trouble being judgy of other people. Once I construct my morals, I can absolutely judge other people by my standards. And I will try to persuade them that my standards are good ones and we'll see how far that goes, but there's no guarantee of success.

Lucas Perry: Right. And there's no ultimately third person true or false answers. There's only what has been constructed given my framework.

Sean Carroll: That's right.

Lucas Perry: So this is then coherent within this other epistemological framework you have of the algorithmic compression of things. And so metaethics leads to algorithmic compression of morality into some system which I can then apply from the folk ontology.

Sean Carroll: Yeah. I'll have some impressions about things that I feel intuitively are right or wrong, but I don't stop there. I realized that, well, I'm trying to live according to some principles, but I haven't yet articulated what they are. And when I do try to articulate what they are, I might realize that some of my initial impulses were wrong and I should fix them. And I can do that. I can update on that basis.

Lucas Perry: All right. Well, hey, thank you so much, Sean. This has been a lot of fun. It's definitely shifted a lot of my opinions. And it's really a pleasure to talk with you and have you here. If people want to check you out, check out the Mindscape Podcast, your new books, follow you on Twitter. Where are the best places to do that?

Sean Carroll: The one stop shopping is my website, So that's where the podcast lives. Mindscape Podcast is available wherever podcasts are available, but there is a webpage on my site. And Twitter, Sean M. Carroll is where I'm most active these days. I still have a blog, but I don't use it that much. So between Twitter, podcasts and the book, that's where you'll find most of my words coming out.

Lucas Perry: All right, Sean. Well, thanks so much.

Sean Carroll: All right. Thanks for having me Lucas, take care.

View transcript

Sign up for the Future of Life Institute newsletter

Join 40,000+ others receiving periodic updates on our work and cause areas.
cloudmagnifiercrossarrow-up linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram