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TED2014

David Chalmers: How do you explain consciousness?

March 18, 2014

Our consciousness is a fundamental aspect of our existence, says philosopher David Chalmers: “There’s nothing we know about more directly…. but at the same time it’s the most mysterious phenomenon in the universe.” He shares some ways to think about the movie playing in our heads.

David Chalmers - Philosopher
In his work, David Chalmers explores the “hard problem of consciousness" -- the quest to explain our subjective experience. Full bio

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Right now
00:12
you have a movie playing inside your head.
00:14
It's an amazing multi-track movie.
00:17
It has 3D vision and surround sound
00:20
for what you're seeing and hearing right now,
00:23
but that's just the start of it.
00:26
Your movie has smell and taste and touch.
00:28
It has a sense of your body,
00:33
pain, hunger, orgasms.
00:36
It has emotions,
00:40
anger and happiness.
00:42
It has memories, like scenes from your childhood
00:46
playing before you.
00:50
And it has this constant voiceover narrative
00:52
in your stream of conscious thinking.
00:57
At the heart of this movie is you
01:01
experiencing all this directly.
01:06
This movie is your stream of consciousness,
01:11
the subject of experience
01:16
of the mind and the world.
01:18
Consciousness is one of the fundamental facts
01:23
of human existence.
01:25
Each of us is conscious.
01:27
We all have our own inner movie,
01:30
you and you and you.
01:33
There's nothing we know about more directly.
01:35
At least, I know about my consciousness directly.
01:39
I can't be certain that you guys are conscious.
01:43
Consciousness also is what makes life worth living.
01:47
If we weren't conscious, nothing in our lives
01:50
would have meaning or value.
01:54
But at the same time, it's the most
01:57
mysterious phenomenon in the universe.
01:58
Why are we conscious?
02:02
Why do we have these inner movies?
02:06
Why aren't we just robots
02:07
who process all this input,
02:10
produce all that output,
02:12
without experiencing the inner movie at all?
02:14
Right now, nobody knows the answers
02:18
to those questions.
02:20
I'm going to suggest that to integrate consciousness
02:22
into science, some radical ideas may be needed.
02:26
Some people say a science of consciousness
02:30
is impossible.
02:33
Science, by its nature, is objective.
02:35
Consciousness, by its nature, is subjective.
02:39
So there can never be a science of consciousness.
02:42
For much of the 20th century, that view held sway.
02:47
Psychologists studied behavior objectively,
02:50
neuroscientists studied the brain objectively,
02:54
and nobody even mentioned consciousness.
02:58
Even 30 years ago, when TED got started,
03:02
there was very little scientific work
03:04
on consciousness.
03:07
Now, about 20 years ago,
03:09
all that began to change.
03:11
Neuroscientists like Francis Crick
03:14
and physicists like Roger Penrose
03:17
said now is the time for science
03:19
to attack consciousness.
03:22
And since then, there's been a real explosion,
03:24
a flowering of scientific work
03:27
on consciousness.
03:29
And this work has been wonderful. It's been great.
03:30
But it also has some fundamental
03:32
limitations so far.
03:34
The centerpiece
03:38
of the science of consciousness in recent years
03:40
has been the search for correlations,
03:43
correlations between certain areas of the brain
03:45
and certain states of consciousness.
03:48
We saw some of this kind of work
03:52
from Nancy Kanwisher and the wonderful work
03:54
she presented just a few minutes ago.
03:55
Now we understand much better, for example,
03:59
the kinds of brain areas that go along with
04:02
the conscious experience of seeing faces
04:04
or of feeling pain
04:08
or of feeling happy.
04:11
But this is still a science of correlations.
04:13
It's not a science of explanations.
04:16
We know that these brain areas
04:20
go along with certain kinds of conscious experience,
04:22
but we don't know why they do.
04:26
I like to put this by saying
04:30
that this kind of work from neuroscience
04:32
is answering some of the questions
04:36
we want answered about consciousness,
04:37
the questions about what certain brain areas do
04:39
and what they correlate with.
04:43
But in a certain sense, those are the easy problems.
04:45
No knock on the neuroscientists.
04:48
There are no truly easy
problems with consciousness.
04:51
But it doesn't address the real mystery
04:53
at the core of this subject:
04:58
why is it that all that physical processing in a brain
05:00
should be accompanied by consciousness at all?
05:04
Why is there this inner subjective movie?
05:07
Right now, we don't really have a bead on that.
05:10
And you might say,
05:13
let's just give neuroscience a few years.
05:15
It'll turn out to be another emergent phenomenon
05:19
like traffic jams, like hurricanes,
05:23
like life, and we'll figure it out.
05:28
The classical cases of emergence
05:30
are all cases of emergent behavior,
05:32
how a traffic jam behaves,
05:36
how a hurricane functions,
05:38
how a living organism reproduces
05:39
and adapts and metabolizes,
05:42
all questions about objective functioning.
05:45
You could apply that to the human brain
05:48
in explaining some of the behaviors
05:50
and the functions of the human brain
05:52
as emergent phenomena:
05:54
how we walk, how we talk, how we play chess,
05:55
all these questions about behavior.
06:00
But when it comes to consciousness,
06:02
questions about behavior
06:04
are among the easy problems.
06:06
When it comes to the hard problem,
06:09
that's the question of why is it
06:10
that all this behavior
06:12
is accompanied by subjective experience?
06:14
And here, the standard paradigm
06:17
of emergence,
06:19
even the standard paradigms of neuroscience,
06:21
don't really, so far, have that much to say.
06:24
Now, I'm a scientific materialist at heart.
06:28
I want a scientific theory of consciousness
06:32
that works,
06:36
and for a long time, I banged my head
06:38
against the wall
06:41
looking for a theory of consciousness
06:42
in purely physical terms
06:44
that would work.
06:46
But I eventually came to the conclusion
06:47
that that just didn't work for systematic reasons.
06:49
It's a long story,
06:53
but the core idea is just that what you get
06:55
from purely reductionist explanations
06:58
in physical terms, in brain-based terms,
07:00
is stories about the functioning of a system,
07:03
its structure, its dynamics,
07:05
the behavior it produces,
07:07
great for solving the easy problems —
07:09
how we behave, how we function —
07:11
but when it comes to subjective experience —
07:14
why does all this feel like
something from the inside? —
07:17
that's something fundamentally new,
07:21
and it's always a further question.
07:23
So I think we're at a kind of impasse here.
07:27
We've got this wonderful, great chain of explanation,
07:32
we're used to it, where physics explains chemistry,
07:35
chemistry explains biology,
07:39
biology explains parts of psychology.
07:42
But consciousness
07:46
doesn't seem to fit into this picture.
07:47
On the one hand, it's a datum
07:50
that we're conscious.
07:52
On the other hand, we don't know how
07:54
to accommodate it into our
scientific view of the world.
07:55
So I think consciousness right now
07:59
is a kind of anomaly,
08:01
one that we need to integrate
08:04
into our view of the world, but we don't yet see how.
08:06
Faced with an anomaly like this,
08:10
radical ideas may be needed,
08:11
and I think that we may need one or two ideas
08:15
that initially seem crazy
08:18
before we can come to grips with consciousness
08:20
scientifically.
08:23
Now, there are a few candidates
08:25
for what those crazy ideas might be.
08:27
My friend Dan Dennett, who's here today, has one.
08:29
His crazy idea is that there is no hard problem
08:34
of consciousness.
08:36
The whole idea of the inner subjective movie
08:38
involves a kind of illusion or confusion.
08:41
Actually, all we've got to do is explain
08:46
the objective functions, the behaviors of the brain,
08:48
and then we've explained everything
08:51
that needs to be explained.
08:53
Well I say, more power to him.
08:55
That's the kind of radical idea
08:58
that we need to explore
09:00
if you want to have a purely reductionist
09:02
brain-based theory of consciousness.
09:04
At the same time, for me and for many other people,
09:08
that view is a bit too close to simply
09:10
denying the datum of consciousness
09:11
to be satisfactory.
09:14
So I go in a different direction.
09:15
In the time remaining,
09:18
I want to explore two crazy ideas
09:19
that I think may have some promise.
09:22
The first crazy idea
09:26
is that consciousness is fundamental.
09:28
Physicists sometimes take
some aspects of the universe
09:32
as fundamental building blocks:
09:35
space and time and mass.
09:37
They postulate fundamental laws governing them,
09:41
like the laws of gravity or of quantum mechanics.
09:45
These fundamental properties and laws
09:48
aren't explained in terms of anything more basic.
09:51
Rather, they're taken as primitive,
09:54
and you build up the world from there.
09:57
Now sometimes, the list of fundamentals expands.
10:00
In the 19th century, Maxwell figured out
10:05
that you can't explain electromagnetic phenomena
10:08
in terms of the existing fundamentals —
10:11
space, time, mass, Newton's laws —
10:13
so he postulated fundamental laws
10:16
of electromagnetism
10:19
and postulated electric charge
10:21
as a fundamental element
10:23
that those laws govern.
10:25
I think that's the situation we're in
10:28
with consciousness.
10:31
If you can't explain consciousness
10:33
in terms of the existing fundamentals —
10:35
space, time, mass, charge —
10:38
then as a matter of logic,
you need to expand the list.
10:40
The natural thing to do is to postulate
10:44
consciousness itself as something fundamental,
10:46
a fundamental building block of nature.
10:49
This doesn't mean you suddenly
can't do science with it.
10:52
This opens up the way for you to do science with it.
10:55
What we then need is to study
10:59
the fundamental laws governing consciousness,
11:01
the laws that connect consciousness
11:04
to other fundamentals: space, time, mass,
11:06
physical processes.
11:09
Physicists sometimes say
11:12
that we want fundamental laws so simple
11:14
that we could write them on the front of a t-shirt.
11:17
Well I think something like that is the situation
11:21
we're in with consciousness.
11:23
We want to find fundamental laws so simple
11:24
we could write them on the front of a t-shirt.
11:27
We don't know what those laws are yet,
11:29
but that's what we're after.
11:31
The second crazy idea
11:35
is that consciousness might be universal.
11:37
Every system might have some degree
11:41
of consciousness.
11:44
This view is sometimes called panpsychism:
11:48
pan for all, psych for mind,
11:51
every system is conscious,
11:54
not just humans, dogs, mice, flies,
11:55
but even Rob Knight's microbes,
12:00
elementary particles.
12:02
Even a photon has some degree of consciousness.
12:04
The idea is not that photons are intelligent
12:07
or thinking.
12:11
It's not that a photon
12:12
is wracked with angst
12:13
because it's thinking, "Aww, I'm always
buzzing around near the speed of light.
12:15
I never get to slow down and smell the roses."
12:18
No, not like that.
12:21
But the thought is maybe photons might have
12:23
some element of raw, subjective feeling,
12:26
some primitive precursor to consciousness.
12:29
This may sound a bit kooky to you.
12:33
I mean, why would anyone think such a crazy thing?
12:36
Some motivation comes from the first crazy idea,
12:39
that consciousness is fundamental.
12:42
If it's fundamental, like space and time and mass,
12:44
it's natural to suppose that it might be universal too,
12:49
the way they are.
12:51
It's also worth noting that although the idea
12:53
seems counterintuitive to us,
12:55
it's much less counterintuitive to people
12:57
from different cultures,
13:00
where the human mind is seen as much more
13:02
continuous with nature.
13:03
A deeper motivation comes from the idea that
13:06
perhaps the most simple and powerful way
13:10
to find fundamental laws connecting consciousness
13:12
to physical processing
13:14
is to link consciousness to information.
13:16
Wherever there's information processing,
13:19
there's consciousness.
13:21
Complex information processing, like in a human,
13:22
complex consciousness.
13:25
Simple information processing,
13:27
simple consciousness.
13:29
A really exciting thing is in recent years
13:31
a neuroscientist, Giulio Tononi,
13:33
has taken this kind of theory
13:36
and developed it rigorously
13:37
with a mathematical theory.
13:40
He has a mathematical measure
13:41
of information integration
13:43
which he calls phi,
13:45
measuring the amount of information
13:47
integrated in a system.
13:48
And he supposes that phi goes along
13:50
with consciousness.
13:52
So in a human brain,
13:54
incredibly large amount of information integration,
13:55
high degree of phi,
13:57
a whole lot of consciousness.
13:59
In a mouse, medium degree
of information integration,
14:01
still pretty significant,
14:05
pretty serious amount of consciousness.
14:06
But as you go down to worms,
14:08
microbes, particles,
14:10
the amount of phi falls off.
14:13
The amount of information integration falls off,
14:15
but it's still non-zero.
14:17
On Tononi's theory,
14:19
there's still going to be a non-zero degree
14:21
of consciousness.
14:23
In effect, he's proposing a fundamental law
14:25
of consciousness: high phi, high consciousness.
14:27
Now, I don't know if this theory is right,
14:31
but it's actually perhaps the leading theory right now
14:33
in the science of consciousness,
14:37
and it's been used to integrate a whole range
14:38
of scientific data,
14:40
and it does have a nice property
that it is in fact simple enough
14:43
you can write it on the front of a t-shirt.
14:45
Another final motivation is that
14:48
panpsychism might help us to integrate
14:51
consciousness into the physical world.
14:53
Physicists and philosophers have often observed
14:56
that physics is curiously abstract.
14:59
It describes the structure of reality
15:02
using a bunch of equations,
15:04
but it doesn't tell us about the reality
15:06
that underlies it.
15:09
As Stephen Hawking puts it,
15:11
what puts the fire into the equations?
15:13
Well, on the panpsychist view,
15:17
you can leave the equations of physics as they are,
15:19
but you can take them to be describing
15:22
the flux of consciousness.
15:23
That's what physics really is ultimately doing,
15:25
describing the flux of consciousness.
15:27
On this view, it's consciousness
15:30
that puts the fire into the equations.
15:31
On that view, consciousness doesn't dangle
15:35
outside the physical world
15:37
as some kind of extra.
15:39
It's there right at its heart.
15:40
This view, I think, the panpsychist view,
15:44
has the potential to transfigure our relationship
15:47
to nature,
15:50
and it may have some pretty serious social
15:51
and ethical consequences.
15:54
Some of these may be counterintuitive.
15:57
I used to think I shouldn't eat anything
15:59
which is conscious,
16:02
so therefore I should be vegetarian.
16:05
Now, if you're a panpsychist and you take that view,
16:08
you're going to go very hungry.
16:10
So I think when you think about it,
16:13
this tends to transfigure your views,
16:14
whereas what matters for ethical purposes
16:16
and moral considerations,
16:19
not so much the fact of consciousness,
16:20
but the degree and the complexity of consciousness.
16:23
It's also natural to ask about consciousness
16:27
in other systems, like computers.
16:29
What about the artificially intelligent system
16:32
in the movie "Her," Samantha?
16:34
Is she conscious?
16:37
Well, if you take the informational,
16:38
panpsychist view,
16:40
she certainly has complicated information processing
16:41
and integration,
16:45
so the answer is very likely yes, she is conscious.
16:46
If that's right, it raises pretty serious
16:49
ethical issues about both the ethics
16:52
of developing intelligent computer systems
16:54
and the ethics of turning them off.
16:57
Finally, you might ask about the consciousness
17:00
of whole groups,
17:03
the planet.
17:05
Does Canada have its own consciousness?
17:06
Or at a more local level,
17:09
does an integrated group
17:11
like the audience at a TED conference,
17:13
are we right now having a
collective TED consciousness,
17:15
an inner movie
17:18
for this collective TED group
17:20
which is distinct from the inner movies
17:23
of each of our parts?
17:24
I don't know the answer to that question,
17:25
but I think it's at least one
17:28
worth taking seriously.
17:29
Okay, so this panpsychist vision,
17:31
it is a radical one,
17:34
and I don't know that it's correct.
17:36
I'm actually more confident about
17:38
the first crazy idea,
17:40
that consciousness is fundamental,
17:41
than about the second one,
17:43
that it's universal.
17:45
I mean, the view raises any number of questions,
17:47
has any number of challenges,
17:50
like how do those little bits
17:51
of consciousness add up
17:52
to the kind of complex consciousness
17:54
we know and love.
17:56
If we can answer those questions,
17:59
then I think we're going to be well on our way
18:00
to a serious theory of consciousness.
18:02
If not, well, this is the hardest problem perhaps
18:05
in science and philosophy.
18:08
We can't expect to solve it overnight.
18:10
But I do think we're going to figure it out eventually.
18:14
Understanding consciousness is a real key, I think,
18:17
both to understanding the universe
18:20
and to understanding ourselves.
18:23
It may just take the right crazy idea.
18:25
Thank you.
18:28
(Applause)
18:30

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David Chalmers - Philosopher
In his work, David Chalmers explores the “hard problem of consciousness" -- the quest to explain our subjective experience.

Why you should listen

David Chalmers is a philosopher at the Australian National University and New York University. He works in philosophy of mind and in related areas of philosophy and cognitive science. While he's especially known for his theories on consciousness, he's also interested (and has extensively published) in all sorts of other issues in the foundations of cognitive science, the philosophy of language, metaphysics and epistemology.

Chalmers placed the "hard problem" of consciousness firmly on the philosophical map. He famously challenges materialist conceptions of mind, arguing for an "explanatory gap" between our brains’ physical properties and our minds’ qualia. Elsewhere he has championed the notion of the "extended mind," which argues that the mind is not confined to skin or skull, but plausibly may extend beyond them.

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