What Exists？ ｜ Episode 1710 ｜ Closer To Truth

Raw existence troubles me. I'm bothered by ultimate questions. Bothered? To be honest, I'm obsessed. What's the cosmos all about? I do normal things of life, but ultimate questions are never much out of mind. What's a theory of everything? Is anything beyond the physical world? Does God exist? Why is there something rather than nothing? Pursuing each ultimate question, I hit a wall. Is there another way, another kind of question, even more basic? How to probe bedrock reality of all existence? The deep question is curt. It's just a short sentence. What exists? I'm Robert Lawrence Kuhn, and Closer to Truth is my journey to find out. Lots of things exist, of course, but the meaning I seek resides in categories of existence. So here's my challenge. To discern the minimum number of categories that contain everything that exists. Some offer diverse ways of perceiving reality, but trained as a scientist, I start with science. Fundamental physics, in particular. That's why I've come to Banff in the Canadian Rockies. It's a gathering of quantum physicists and cosmologists. Philosophers, too. Members of the Foundational Questions Institute, FQXI, where serious scientists challenge conventional wisdom. I begin with a theoretical physicist who explores the deep essence of time and space, Sean Carroll. I like that Sean asserts a wholly physicalist worldview, and that he's ready to take on any who don't. Sean, I want to understand everything. I'm not sure how they all may fit together, but I want to have everything on the table so I know what I have to deal with. And so the question I like to ask, what are the most fundamental categories that we can classify reality in its total sense? So, how do you start? My best guess is that the universe is a quantum mechanical wave function, and that that is all that exists. The wave function either is all there is at all, or maybe there's a wave function evolving over time. And it's a little bit tricky, because when we talk about quantum mechanical wave function, someone's going to want to say a wave function of what? I talk about the wave function of an electron, the wave function of a chemical gas or whatever. My attitude is it's the other way around, that there is just a quantum mechanical wave function, and we can talk about it in different ways. I think a lot of ideas from modern quantum gravity have really emphasized this. The same quantum thing can be sliced in different ways to give different physical objects. And sort of the art form of describing the world is looking at a quantum wave function and figuring out why is it useful to describe it as tables and chairs and people and planets. What does that literally mean, a quantum wave form of the universe? Is it one big thing that describes everything, or is it one big thing that has little quantum wave forms that comes out of it? It's both at once. That's the miracle kind of of quantum mechanics. The interesting thing about quantum mechanics is one of the things that makes it difficult to understand at first glance, there aren't separate quantum wave functions for different parts of the universe. In classical mechanics, you have a baseball here, a baseball bat, you talk about the state of the baseball, you talk about the state of the bat. In quantum mechanics, there's not a wave function of the baseball and a wave function of the bat. There's a wave function for the baseball plus bat system. And in fact, there's only one wave function for the entire universe all at once. And then you say, well, but then I divide it up. I think of this big wave function for the universe as a combination of little systems, one for the baseball, one for the bat, one for the batter, et cetera. That's perfectly good. Someone else comes along and says, I want to divide it up a different way. And you say, why did you do it this way versus that way? The embarrassing truth is we don't know the answer to that question yet. But when you're doing that, are you doing that as a form of understanding it in a simplistic way or is that an attempt to get what's really happening and people have different views of what's really happening? My view is that it's not a way of getting at what's really happening. In fact, what's really happening is this abstract mathematical thing, the wave function. I think the point is that if you buy this story that that's all that there is, is this wave function evolving in time, there's no extra explanatory level that says, well, why is there a wave function evolving in time? Which is the typical answer that people give about God if you ask where did God come from. It's not exactly the same because they would go on to say that God is a necessary part of the universe. Whereas the fact that the universe is a wave function evolving in time is deeply contingent. I make no claims that it had to be that way. That's the way it is. Okay, but you're saying that it is contingent or you're saying you don't know whether it's contingent or necessary? I can't imagine that it's necessary. You can't imagine it. I can easily imagine other kinds of universes that are not that and our universe is this one. Let's explore that. Is it the same wave function that encompasses the entire multiverse or are you eliminating the wave function to each individual separate universe? The footnote for every single question here is we don't know for sure. But in my view, it's one wave function for all the different parts of what we call the multiverse. So, that becomes even more important to where did that come from? Well, but it also becomes important that we can't demand an answer to that question. We can look for an answer, but we can't say I insist. I am at peace with the idea that it simply is. Deeply contingent. Well, I would find that hard to be at peace with, as something that significant. It's a free country. To be deeply contingent. I think if there's any one lesson of quantum mechanics and modern physics, it's that we need to be open to weird, bizarre ways that the universe is from our individualistic perspective. I'd be happier if there were some ultimate, clean and irresistible explanation for it, but I certainly don't think I have the right to insist. You don't demand it, because I'm in the state where I need to demand it. And I want to minimize the things I demand of the universe. So, all reality to you can be contingent. Yes. So, it is entirely logical that there could have been absolutely nothing. That's right. And I think that it's a consistent point of view in the sense that when we talk about reasons and causes and explanations, these are, again, ancient words that we repurpose. And maybe these don't apply in modern quantum physics. It's hard for me to imagine that something so complicated and so integrated is the radically contingent totality of reality. Yep. I'm very sympathetic to that. And so, part of that is that, you know, we physicists would like to find a simpler, more beautiful underlying pattern that explains the sort of messiness of the pattern that we do observe. We can still have that goal for a simpler explanation, but that simpler explanation would then just be what it is. And still be contingent, in your view. Sean sees all reality as one thing, the quantum mechanical wave function, encompassing the universe and multiple universes and evolving over time, generating probabilities of all events everywhere. The parsimony is arresting and appealing. I prize simplicity. And in seeking a minimum number of categories of what exists, you can't get simpler than one thing. But how could that one thing, utter simplicity, generate unimaginable complexity? Could physics have another problem as well? It's called consciousness, how mental states feel inside. Could consciousness be fundamental, a basic building block of all reality, an irreducible category of what exists? I speak with a leading philosopher of mind who famously coined the hard problem of consciousness, David Chalmers. I'm thrilled to see Dave at his first FQXI conference. Could philosophy of mind be relevant for fundamental physics? If so, then would the categories of what exists have to expand to include consciousness? Dave, what are the categories in which we can classify at the most fundamental level all the things that there are? All, not just physics. Whatever there is that literally exists, how can we classify it? Some people say the fundamental things that exist are physical things, in particular the entities of physics. The quarks, the photons, the associated forces, and so on. So that's the physicalist view. And that's one view. Now for me, as a philosopher of consciousness, I'm inclined to think that leaves the mind out. You can't explain consciousness out of just those entities of physics. So it leads me to a more radical view in some way, where among the fundamental things that exist is consciousness. And in fact, both physics and consciousness need to be taken as fundamental. One really interesting question is whether those might somehow be reconciled into one basic underlying category. In physics, they talk about the grand unified theory that will bring together relativity and quantum mechanics and all the different forces. Well, let's take that one step further. Could there be a grand unified theory that brings consciousness into the mix too? Philosophers sometimes talk about neutral monism, the idea there's some basic thing that might underlie all. Monism being one thing. One thing, but yeah, more primitive than physics, more primitive than consciousness that somehow underlies it all. In philosophy, people sometimes talk about the idea there could be some proto-physical, proto-conscious entity that underlies and unifies both physics and consciousness. And that's an idea I'm really interested in. Would it be something that had to exist, necessary in the sense that there'd be no possible world in which that would not exist? That's an interesting question. I'm inclined to think the world is fundamentally contingent, as in it is this way, but it could have been a different way, could have been a radically different way. Even if, for example, there's no God in this world, maybe there could have been a world with a God. Even if this is a world of physics, there could have been a world of just mind. It doesn't have to be this way. It just is this way, and that's kind of a brute contingent feature of reality. There are other things that we have. There's abstract objects. There's mathematics. How do you deal with those kinds of things? I want to have everything. I'm especially interested in natural ontology, the ontology of the natural world, which to me includes both physics and minds and so on. But once you start bringing in mathematics and abstract objects and so on, then they might have an ontology all of their own. I'm inclined. I'm a little bit deflationary about the ontology of mathematics. I don't think numbers have the kind of fundamental existence that, say, particles do or that minds do. Particles are really there. Minds are really there. Are numbers really there? I'm inclined to give kind of a quizzical answer to that question. And that's a legitimate position, of course, but there are people who would take quite the opposite. Oh, yeah. They say the only reality are the abstract objects, and somehow they have generated all this apparent physical and mental stuff. Yeah. I've never seen how you get a concrete world out of a purely abstract world. Some people say that value, the goodness, is something that has creative powers to generate everything else. Can of valuatism. You heard it first here. Now, in the physical piece, you're saying there's just quantum fields and that's it. But when they aggregate themselves into trees and mountains and people, are there differences? I mean, in the case of classical physics, it seemed relatively easy. There were these particles, and you put together particles into clusters of particles, molecules, cells, bodies, and it's all just kind of composition. Now, for quantum mechanics, we run up against the basic worry about quantum mechanics, which is nobody really understands how you get from a quantum mechanical world at the basic level, where everything is this giant wave, to a classical world, where everything seems to be relatively discrete and determinate. And you might say part of that question is understanding the mode of aggregation. How do all these little quantum states add up to a classical state? And that's right at the very heart of quantum mechanics. My own view is that, actually, once you bring the mind in, some of the determinacy of the physical world may actually come from consciousness itself. If you like, you could think of that as a mode of aggregation that is part of the explanation of why you have a classical world that looks like this, with mountains and trees and so on, of a discrete and determinate kind, even though the world is fundamentally quantum mechanical. So what do you conclude about what exists at the end of the day? Where are you right now, in terms of fundamental categories? I think consciousness exists, and I think physics exists, and I think they're both fundamental. Are they ultimately the same fundamental category, or are they distinct? That's, for now, an open question. Dave's challenge is bracing. It's like heresy to conventional science. Dave rejects physicalism, the prevailing scientific worldview that the only things that exist are physical. He asserts that consciousness has equal standing with physics, at least equal. And possibly, he says, there's something deeper still, even more fundamental. But I'm not ready to go with Dave to panpsychism, where literally every particle has, or is, consciousness. An extreme solution. Yet, because I do take consciousness seriously, I must consider consciousness a candidate for a what-exists category. I worry, though. Because I want consciousness to be fundamental, are my allowing hope to distort reason? I seek a philosopher of quantum physics who doesn't buy any non-physical stuff. Formerly at Oxford, now at USC, David Wallace. If I want to know what exists at some level of reality, what I'll do is I'll look at our best scientific theories at that level of reality. I don't think we've got any good guide to what exists that trumps our science. So then, the question as to what exists at the most fundamental level of reality is something I better answer by looking at our theory at the most fundamental level of reality. And the problem is we don't have that theory. And one of the lessons we seem to have learned from the development of science in general, and physics in particular, is that when we go from a theory at one level to a theory at a lower level, we're caught really by surprise. It has things in it that we didn't expect, and it takes out things that we kind of expected to stay there. So maybe back in the day we thought, you know, life and mind were fundamental in the world. And they've dropped out entirely by the time you get down to cell biology. Molecular biology. And then maybe we thought persisting objects and solid matter was a fundamental part of the world. That drops out by the time you get down to atomic physics. So, I think the goal of looking for what's fundamental I think is premature. Maybe, maybe if we're optimistic we're starting to get an inkling as to what fundamental theories would look like. But lots of people have thought that before, and they've been wrong. I've heard some people say that there could be an infinite regress of theories all the way down. That doesn't make sense to me. Does that make sense to you? It doesn't really make sense to me. Having said which, I don't really trust what makes sense to me in these contexts. I think we've got good reason to expect that's probably not how things are. Partly skepticism about whether it makes sense, partly the fact that our physics seems to be converging down to one description that we stop at, but we don't know that yet, and we know not so much about what that description looks like. We've got an inkling, but perhaps not much more. Would that have to be very simple? Or could it have a lot of complexity? Because some people think quantum mechanics is the fundamental category and quantum mechanics is very complicated. Complexity is a little bit in the eye of the beholder. As a physicist, I think physics is pretty simple and biochemistry is amazingly complicated. I don't know how they can do all that stuff. There's so many different bits of it. Physics is really abstract and the mathematics of its descriptions take a lot of effort to bend your mind around, but in many respects physical theories are pretty simple. You can almost literally write them on t-shirts. It can't get too simple. The world we live in is complicated and the theory has to have enough complexity to allow that emerging complexity of our world to turn up. But we've learnt a lot about how really simple theories can generate really complex outputs. Really simple computer programs can produce incredible patterns. It could be pretty simple, I think. You've given me a thorough understanding of what exists or what could exist from a scientific point of view accessible to science. The question is, is that all that exists? I'll give you some other categories and see how you like them. There are abstract objects, universals, mathematics, logic, propositions, a whole set of things, platonic, if you believe in that. There are things that are non-physical that people claim, cosmic consciousness, spirit regions, God. I just want to get my arms around everything. Okay, I see your point. I don't think there's a platonic realm of mathematical objects and that's been paradoxical for a long time. I think mathematics is a science of structure and I expect when we get our head around mathematics from a philosophical point of view we won't do it via this world of platonic objects. And the reason I say that is the reason why less tentatively I'm pretty sure we won't have these non-physical things either, which is that anything that just doesn't interact causally with the world we're in, it's very hard to see how we could get information and knowledge about it. But those are two different things. One is epistemological in terms of knowing it, the other is ontological whether there really is it. The fact that we can't know it doesn't mean it's not there. Sure, okay. I agree, but only in a minimal sense. I mean, if you like, there's a big catch-all category of things that we'll never have any way of knowing about. And I suppose there might be things in that category, I'll never have a way of knowing. But the sort of things that you're describing aren't really in that category. The idea of these mathematical objects is that somehow they're relevant explanatory to math. The idea of consciousness is that somehow it's relevant explanatory to a physical notion. That's what I don't think works. If consciousness doesn't interact with the physical, and we've got pretty good reason to think it doesn't, then when I say to you, I'm conscious, when we have this conversation, when people passionately say that they have this deep intuition that they are conscious and that there's more to their consciousness than mere physical processes, we know, by the way the question's been set up, that the mere physical processes underlie their saying that, and they'd be just as passionate if there were none of this extra physical consciousness. So, I don't really think it makes sense to have things like that coming in. Sure. But what you're saying now is controversial, obviously. Massively. Well, I guess I'm going to be a bit more skeptical. I think that category is kind of equivocating between a category of things that we genuinely have no access to, which I'm agreeing could exist, but we just can't profitably talk about, and a category of things that are supposed to be playing some genuine explanatory role even though we can't get at them. And I'm saying of that second category, although you're dead right this is controversial, that I don't think that category is coherent. So it's not just that I think it's empty, I don't think it really makes sense to talk about it. David is an arch-physicalist. Reality is only that which is accessible to science, and only that. I respect his logical purity, his skepticism of anything non-physical, his expectation of surprise when digging deeper into reality, and his call for caution in trusting what seems to make sense. Why then do I find myself resisting physicalism, challenging the natural conclusion that the only real categories of what exists are physical? As justification for my challenge, if not as evidence, I submit consciousness. But there's more. I cannot deny an inquisitive curiosity about possible non-physical existence. To explore non-physical existence, if they exist, I turn to a quantum physicist who unabashedly asserts his belief in God, Don Page. Don, you have a bigger version of what things exist in all reality. Yes, okay. Well, of course, there's a platonic existence of logical truths such as mathematical theorems, but let me go on to the things that I don't believe are logically necessary. But I guess for me as a Christian, first I would believe in God, and God the Father, God the Son, God the Holy Spirit. So that's a category of God? Yes. So there's a category of God, and there's a category of the universe or multiverse, and then there's a category of other things that God may have created. So there's like three categories. And I guess within this, I might say, well, for God, I think there's a benevolence of, you might even say, using sort of an ethical requirement to create the best possible world consistent with his nature. And then there's, I believe, omniscience of knowing what the best would be. Okay, so that's a God category. Second, you say there's a multiverse in some sense, you know, the physical existence. Right. And for that, here I'm sort of laying out what is the primary existence. And so I think in some sense, I think most primary are the sentient experiences we have, that the consciousness we have. And then I— but I do believe that the way that this is connected with physics is that for each sentient experience, there's what we call in quantum theory a positive quantum operator. And so for example, I know from introspection that I have sentient experiences, and I very strongly believe that you and other humans also do, and I believe pets do, and higher animals, and probably to a lower degree, even the lower ones. So these are all in your second category. Yes, this is in the second category. And so where you at first said multiverse, what you really mean more complex is the sentient experience, almost a creation in a way of the multiverse. But God created it, the God category, now the multiverse category. So what's very interesting to me is that you did not separate out consciousness and the multiverse as two separate categories that God created, but you in fact had them as one category. Yes, I believe that they're very strongly related. We don't know the laws of psychophysical parallelism. How do you get from one? As I say, I have a framework where it's expectation values of operators that give the measure of conscious perceptions. That's a framework, but not a theory because I don't know what these operators are. What other things have God created? People talk about platonic objects. And of course, I don't know what God has created. Now, I will say, I guess by my own view, this platonic thing of mathematical truths, I think that they just exist as logical necessities, and they can't be created or destroyed. So those things, I think, have sort of a fuzzy existence, but that's apart from God. They have their sort of abstract existence independent of God. Now, of course, God can use them. So I believe, yeah, God and our universe and then other entities that God has created. What exists? Here are four kinds of basic categories of what exists. One, the physical world alone, nothing more. Perhaps the quantum wave function or something surprising that's more fundamental. Two, consciousness is fundamental, perhaps on a par with physics or the manifestation of a deeper reality or itself the ultimate reality. Three, add possible passive non-physical existence like abstract objects. Four, add possible active non-physical existence like God. I relish the diversity of the four kinds of categories. I applaud the divergence. But don't diversity and divergence mean we are further from truth? No. By exposing the false narrative that we know what exists for sure, diversity and divergence bring us closer to truth.