[music] <i> Raw existence troubles me.</i> <i> I'm bothered by ultimate
questions. Bothered.</i> <i> To be honest, I'm obsessed!</i> <i> What's the cosmos all about?</i> <i> I do normal things of life,</i> <i> but ultimate questions are
never much out of mind.</i> <i> What's the Theory
of Everything?</i> <i> Is anything beyond
the physical world?</i> <i> Does God exist?</i> <i> Why is there something
rather than nothing?</i> <i>Pursuing each ultimate question,
I hit a wall.</i> <i> Is there another way,</i> <i> another kind of question
even more basic?</i> <i> How to probe bedrock
reality of all existence?</i> <i> The deep question is curt.</i> <i> It's just a short sentence:
what exists?</i> <i> What exists!</i> <i> I'm Robert Lawrence Kuhn,</i> <i> and Closer To Truth is
my journey to find out.</i> Lots of things exist, of course, but the meaning I seek resides
in categories of existence, so here's my challenge: <i> to discern the minimum
number of categories</i> <i> that contain everything
that exists.</i> <i> Some offer diverse ways
of perceiving reality,</i> <i> but trained as a scientist,
I start with science,</i> <i> fundamental physics
in particular.</i> <i> That's why I've come to Banff
in the Canadian Rockies.</i> <i> It's a gathering of quantum
physicists and cosmologists;</i> <i> philosophers, too.</i> <i> Members of the Foundational
Questions Institute, FQXi,</i> <i> where serious scientists
challenge conventional wisdom.</i> <i> I begin with a
theoretical physicist</i> <i> who explores the deep essence
of time and space, Sean Carroll.</i> <i> I like that Sean asserts a
wholly physicalist world view</i> <i> and that he's ready to
take on any who don't.</i> <i> Sean,</i> 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 it is a wave
function evolving over time, and it's a little bit tricky because when we talk about quantum mechanical
wave functions, someone's going to want to say:
a wave function of what? I talk about the wave
function of 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, so 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
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, 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, etcetera,
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 <i> as a form of</i> 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 over 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 go on to say that God is a necessary part of
the universe. -Right, right. 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 are you saying you don't know whether it's contingent
or necessary? I can't imagine
that it's necessary. You 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 limiting
the wave function to each individual
separate universe? No, 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's [Cross talk]. Deeply contingent. Well, I would find that
hard to be at peace with. Something that significant...
-It's a free country. ...to be deeply contingent. I think if there's
any one lesson of quantum mechanics
in 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... 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. Yup. I'm very
sympathetic to that. 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...
-Sure, sure. ...but that simpler explanation
will then just be what it is. And still be contingent
in your view? [music] <i> Sean sees all
reality as one thing:</i> <i> the quantum mechanical
wave function,</i> <i> encompassing the universe
and multiple universes</i> <i> and evolving over time,</i> <i> generating probabilities
of all events everywhere.</i> <i> The parsimony is arresting,
and appealing.</i> <i> I prize simplicity,</i> <i>and in seeking a minimum number
of categories of what exists,</i> <i> you can't get simpler
than one thing.</i> <i> But how could that one thing,
utter simplicity,</i> <i> generate unimaginable
complexity?</i> <i> Could physics have
another problem, as well?</i> <i> It's called consciousness:
how mental states feel inside.</i> <i> Could consciousness
be fundamental;</i> <i> a basic building block
of all reality,</i> <i> an irreducible category
of what exists?</i> <i> I speak with a leading
philosopher of mind</i> <i> who famously coined the hard
problem of consciousness,</i> <i> David Chalmers.</i> <i> I'm thrilled to see David at
his first FQXi Conference.</i> <i> Could philosophy
of mind be relevant</i> <i> for fundamental physics?</i> <i> If so, then would
the categories of</i> <i> what exist have to expand
to include consciousness?</i> <i> Dave, what are the categories</i>
in which we can classify, at the most fundamental level, all the things that there are...
all, not just physical, 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 clocks, the photons, the
associated forces, and so on, so that's the physical 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 period 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? For us, I'm talking
about mutual monism; the idea there's some basic
thing that might underlie all... One as in being one thing? One thing, but yeah,
more primitive than physics, more primitive
than consciousness that somehow underlies all, and philosophy people sometimes
talk about the idea there could be
some protophysical, protoconscious entity
that underlies and unifies both physics
and consciousness, and that's an idea I'm
really interested in. Would it be something<i>
that had to exist?</i> <i> Necessary in the sense that</i>
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've been
a different way, could've been a
radically different way. Even if, for example,
there's no God in this world, maybe there could've
been a world with a God. Even if this is a
world of physics, there could've been
a world of just mind. It didn'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 may include 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 and say the only reality
are the abstract objects, and somehow they
have generated all this apparent physical
and mental stuff. Yes, I've never seen how
you get a concrete world out of a purely abstract world. Some people say that value,
that goodness, is something that
has created powers that generate everything else. Power of valuatism. You heard it first here. Okay. Now, in the physical piece, are you saying<i> there's just
quantum fields and that's it,</i> but when they
aggregate themselves into trees and mountains and
people, are there differences? I mean, the case of
classical physics, it seems relatively easy. There are 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 discreet
and determinate. And you might just 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 naturally come from
consciousness itself. If you like, you could think
of that as emotive 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 discreet
and determinant 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. [music] <i> Dave's challenge is bracing.</i> <i> It's like heresy to
conventional science.</i> <i> Dave rejects physicalism,</i> <i> the prevailing
scientific world view</i> <i> that the only things
that exist are physical.</i> <i> He asserts that consciousness
has equal standing</i> <i> with physics, at least equal,</i> <i> and possibly, he says,
there's something deeper,</i> <i> still, even more fundamental.</i> <i> But I'm not ready to go
with Dave to panpsychism,</i> <i> where literally
every particle has,</i> <i> or is, consciousness...
an extreme solution,</i> <i> yet, because I do take
consciousness seriously,</i> <i> I must consider
consciousness a candidate</i> <i> for a what exists category.</i> <i> I worry, though,</i> <i> because I want consciousness
to be fundamental,</i> <i> am I allowing hope
to distort reason?</i> <i> I seek a philosopher
of quantum physics</i> <i> who doesn't buy any
nonphysical stuff.</i> <i> Formerly at Oxford,
now at USC, David Wallace.</i> 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 science. So then, the question is to what exists at the most
fundamental level of reality, something I'd 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 can't have 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,
or 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. We maybe, we were optimistic, we're starting to get an inkling of what fundamental theories
would look like, but lots of people have
thought that before and<i> they've been wrong.</i> 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 didn'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<i> inkling but
perhaps not much more than that.</i> 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. 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. And, of course, I mean,
you 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 learned a lot about
how really simple theories can generate really
complex outputs. Really simple computer programs
can produce incredible patterns. So it can be pretty
simple, I think. So you've given me a
thorough understanding of what exists
or what could exist from a scientific point of view
accessible to science, and the question is,
is that all that exists? And so I'll give you
some other categories and see how you like them, and they are: abstract objects,
universal mathematics, logic, propositions... a
whole set of things,<i> platonic,</i> <i> if you believe in that.</i> <i> Now there are things that are</i>
nonphysical that people claim: cosmic consciousness,
spirit regions, God... and I just want to get my
arms around everything. <i> Okay. I see your point.</i> 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<i> structure</i> <i> and I expect, when we get our
head around mathematics</i> from a philosophical
point of view, we won't do it via this
world of platonic objects. And then the reason I say that is the reason
why less tentatively I'm pretty sure we
won't have these nonphysical 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, and 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 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 supposed 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 mass. The idea of conscious is that <i> somehow it's
relevant explanatory</i> <i> to a physical nature,</i> <i> and that's what
I don't think works.</i> 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 unconscious... 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 has 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. <i> So I don't really
think it make sense</i> <i> to have things like
that coming in. -</i> Sure. But what you're saying now
is controversial, obviously? Oh, massively. Well, I guess I want to
be a bit more skeptical. I think that category
is kind of evocating 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 to them. And I'm saying of
that second category, oh, you're dead right,
it's controversial, but I don't think that
category is coherent. <i> So it's not just that
I think it's empty,</i> <i> I don't think it really makes
sense to talk about it.</i> [music] <i> David is an arch-physicalist.</i> <i> Reality is only that</i> <i> which is accessible to
science and only that.</i> <i> I respect his logical purity.</i> <i> His skepticism at
anything nonphysical,</i> <i> his expectation of surprise</i> <i> when digging deeper
into reality,</i> <i> and his call for
caution in trusting</i> <i> what seems to make sense.</i> <i> Why, then, do I find
myself resisting physicalism,</i> <i> challenging with
actual conclusion</i> <i> that the only real categories
of what exist are physical?</i> <i> As justification
for my challenge,</i> <i> if not his evidence,
I submit consciousness,</i> <i> but there's more.</i> <i> I cannot deny an
inquisitive curiosity</i> <i> about possible
nonphysical existence.</i> <i> To explore nonphysical
existence, if they exist,</i> <i> I turn to a quantum physicist</i> <i> who unabashedly asserts
his belief in God:</i> <i> Don Page.</i> Don, you have a bigger version of what things exist
in all reality. Yes, okay. Well, of course, there's the platonic
existence of logical truths such as mathematical theorems, but let me go onto 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,
and 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 a, you might even say, using sort of an ethical
requirement in us to create the best possible
world consistent with His nature and then there is, I believe, omniscience of knowing
what the best- Okay. So that's a God category. Second, you say, is the
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, 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 is, what we call in quantum theory,
a positive quantum operator. 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, so this is in
the second category. And so where you first
said multiverse, what you really
mean more complex, is the sentient experience, almost a creation, in a way,
of the multiverse. <i> But God created it,
so you have the God category,</i> <i> now the multiverse category,</i> 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
psycho-physical 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. <i> What other things
have God created,</i> 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 of 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 thing,
I think have... well, sort of a fuzzy existence,
but that's apart from God and they have their sort
of abstract existence independent of God. Now, of course, God can
use them, but anyway. So I believe, yeah,
God, our universe, and then other entities
that God has created. [music] <i> What exists?</i> <i> Here are four kinds of basic
categories of what exists:</i> <i> 1) The physical world alone,
nothing more.</i> <i> Perhaps the quantum
wave function,</i> <i> or something surprising
that's more fundamental;</i> <i>2) consciousness is fundamental,</i> <i> perhaps on a par with physics,</i> <i> or the manifestation
of a deeper reality,</i> <i>or itself, the ultimate reality;</i> <i> 3) A possible passive
nonphysical existence</i> <i> like abstract
[inaudible];</i> <i>4) A possible active nonphysical
existence like God.</i> <i> I relish the diversity of the
four kinds of categories.</i> <i> I applaud the divergence.</i> <i> But don't diversity
and divergence mean</i> <i> we are further from truth?</i> <i> No.</i> <i>By exposing the false narrative</i> <i> that we know what
exists for sure,</i> <i> diversity and divergence
bring us closer to truth.</i> [music]
