you have a movie playing inside your head.

It's an amazing multi-track movie.

It has 3D vision and surround sound

for what you're seeing and hearing right now,

but that's just the start of it.

Your movie has smell and taste and touch.

It has a sense of your body,

pain, hunger, orgasms.

It has emotions,

anger and happiness.

It has memories, like scenes from your childhood

playing before you.

And it has this constant voiceover narrative

in your stream of conscious thinking.

At the heart of this movie is you

experiencing all this directly.

This movie is your stream of consciousness,

the subject of experience

of the mind and the world.

Consciousness is one of the fundamental facts

of human existence.

Each of us is conscious.

We all have our own inner movie,

you and you and you.

There's nothing we know about more directly.

At least, I know about my consciousness directly.

I can't be certain that you guys are conscious.

Consciousness also is what makes life worth living.

If we weren't conscious, nothing in our lives

would have meaning or value.

But at the same time, it's the most

mysterious phenomenon in the universe.

Why are we conscious?

Why do we have these inner movies?

Why aren't we just robots

who process all this input,

produce all that output,

without experiencing the inner movie at all?

Right now, nobody knows the answers

to those questions.

I'm going to suggest that to integrate consciousness

into science, some radical ideas may be needed.

Some people say a science of consciousness

is impossible.

Science, by its nature, is objective.

Consciousness, by its nature, is subjective.

So there can never be a science of consciousness.

For much of the 20th century, that view held sway.

Psychologists studied behavior objectively,

neuroscientists studied the brain objectively,

and nobody even mentioned consciousness.

Even 30 years ago, when TED got started,

there was very little scientific work

on consciousness.

Now, about 20 years ago,

all that began to change.

Neuroscientists like Francis Crick

and physicists like Roger Penrose

said now is the time for science

to attack consciousness.

And since then, there's been a real explosion,

a flowering of scientific work

on consciousness.

And this work has been wonderful. It's been great.

But it also has some fundamental

limitations so far.

The centerpiece

of the science of consciousness in recent years

has been the search for correlations,

correlations between certain areas of the brain

and certain states of consciousness.

We saw some of this kind of work

from Nancy Kanwisher and the wonderful work

she presented just a few minutes ago.

Now we understand much better, for example,

the kinds of brain areas that go along with

the conscious experience of seeing faces

or of feeling pain

or of feeling happy.

But this is still a science of correlations.

It's not a science of explanations.

We know that these brain areas

go along with certain kinds of conscious experience,

but we don't know why they do.

I like to put this by saying

that this kind of work from neuroscience

is answering some of the questions

we want answered about consciousness,

the questions about what certain brain areas do

and what they correlate with.

But in a certain sense, those are the easy problems.

No knock on the neuroscientists.

There are no truly easy problems with consciousness.

But it doesn't address the real mystery

at the core of this subject:

why is it that all that physical processing in a brain

should be accompanied by consciousness at all?

Why is there this inner subjective movie?

Right now, we don't really have a bead on that.

And you might say,

let's just give neuroscience a few years.

It'll turn out to be another emergent phenomenon

like traffic jams, like hurricanes,

like life, and we'll figure it out.

The classical cases of emergence

are all cases of emergent behavior,

how a traffic jam behaves,

how a hurricane functions,

how a living organism reproduces

and adapts and metabolizes,

all questions about objective functioning.

You could apply that to the human brain

in explaining some of the behaviors

and the functions of the human brain

as emergent phenomena:

how we walk, how we talk, how we play chess,

all these questions about behavior.

But when it comes to consciousness,

questions about behavior

are among the easy problems.

When it comes to the hard problem,

that's the question of why is it

that all this behavior

is accompanied by subjective experience?

And here, the standard paradigm

of emergence,

even the standard paradigms of neuroscience,

don't really, so far, have that much to say.

Now, I'm a scientific materialist at heart.

I want a scientific theory of consciousness

that works,

and for a long time, I banged my head

against the wall

looking for a theory of consciousness

in purely physical terms

that would work.

But I eventually came to the conclusion

that that just didn't work for systematic reasons.

It's a long story,

but the core idea is just that what you get

from purely reductionist explanations

in physical terms, in brain-based terms,

is stories about the functioning of a system,

its structure, its dynamics,

the behavior it produces,

great for solving the easy problems —

how we behave, how we function —

but when it comes to subjective experience —

why does all this feel like something from the inside? —

that's something fundamentally new,

and it's always a further question.

So I think we're at a kind of impasse here.

We've got this wonderful, great chain of explanation,

we're used to it, where physics explains chemistry,

chemistry explains biology,

biology explains parts of psychology.

But consciousness

doesn't seem to fit into this picture.

On the one hand, it's a datum

that we're conscious.

On the other hand, we don't know how

to accommodate it into our scientific view of the world.

So I think consciousness right now

is a kind of anomaly,

one that we need to integrate

into our view of the world, but we don't yet see how.

Faced with an anomaly like this,

radical ideas may be needed,

and I think that we may need one or two ideas

that initially seem crazy

before we can come to grips with consciousness

scientifically.

Now, there are a few candidates

for what those crazy ideas might be.

My friend Dan Dennett, who's here today, has one.

His crazy idea is that there is no hard problem

of consciousness.

The whole idea of the in