I am going to talk about consciousness.

Why consciousness?

It is curiously a neglected subject

both in our scientific
and our philosophical culture.

Why is that curious?

It's most important aspect of our lives
for a very simple logical reason,

namely, it is a necessary condition
on anything being important in our lives

that we are conscious.

[If] you care about science,
philosophy, music, art, whatever,

it is no good if you are
a zombie or in a coma, right?

So consciousness is number one.

That's the first reason
[that] we are talking about it.

The second reason is that when people
do get interested in it,

as I think they should,

they tend to say
the most appalling things!

I am not going to attempt
to conceal from you

some of the most appalling things
that have been said about it;

and even when they are not saying
appalling things

[and] they are really trying
to do serious research,

well, it's been slow,
progress has been slow.

Let me tell you a little bit
about some of the difficulties.

When I first got interested
in this, I thought

it's a straightforward problem in biology

[so] let's get these brain stabbers
to get busy

and figure out how it works in the brain.

I went over to UCSF and talked
to all heavy-duty neurologists there

and they showed some impatience,

as scientists often do when you ask them
embarrassing questions,

and the thing that struck me

is that a very famous neurobiologist
said exasperated:

"Look, in my discipline,
it's OK to be interested in consciousness,

but get tenure first!

(Laughter)

I've been working on this for a long time

and now you might actually get tenure

by working on consciousness,
and if so, that's a real step forward!

Why then, is this curious reluctance

and curious hostility to consciousness?

I think it's a combination of two features
of our intellectual culture

that like to think
they are opposing each other

but in fact they share
a common set of assumptions.

Consciousness is not a part
of the physical world

but it's part of the spiritual world,
it belongs to the soul,

and the soul is not a part
of the physical world.

That's the tradition of God,
the soul, and immortality.

There is another tradition
that is opposed to this

but excepts the worst assumption.

That tradition thinks
we are heavy-duty scientific materialists,

consciousness is not a part
of the physical world,

either it doesn't exist at all
or it is something else,

a computer program
or some damn fool thing.

(Laughter)

But in any case, it's not part of science!

I used to get in an argument
that really gave me a stomachache.

Here is how it went:

"Science is objective,
consciousness is subjective,

therefore, there cannot be
a science of consciousness."

I love that argument

because it has got
a wonderful fallacy of ambiguity

over the concept of objectivity.

And I have already used up too much time

just to clearing my breath,
sort of speak,

but I want to get to that.

These twin traditions are paralyzing us,

and it's very hard to get out
of these twin traditions,

and I have only one real message
in this lecture,

and that is consciousness

is a biological phenomenon,
like photosynthesis,

digestion, mitosis,
and all that biological phenomena.

And once you accept that,

most, though not all,

of the hard problems about consciousness

simply evaporate!

And I will go through some of them.

I promised you to tell you

some of the outrageous things
said about consciousness,

and because of shortage of time,
I will only mention four of the worst.

One: "Consciousness does not exist.

It is an illusion, like sunsets."

Science has shown sunsets
and rainbows are illusions,

so consciousness is an illusion.

Two: "Maybe it exists,
but it is really something else,

it's a computer program
running in the brain."

Three: "No, the only thing
that exists is really behavior!"

It's embarrassing
how influential behaviorism was,

but I will get back to that.

Four: "Maybe consciousness exists,

but it can't make
any difference to the world.

How could spirituality move anything?"

And whenever somebody
tells me that, I think:

"You want to see if spirituality
moves something? Watch!"

I decide consciously to raise my arm
and the damn thing goes up.

(Laughter)

(Applause)

Furthermore, we do not say:
"It's a bit like the weather in Geneva,

some days it goes up
and some days it doesn't go up."

No! It goes up

when I right damn well want it to!

I will tell you how that is possible.

Now, I haven't yet given you a definition,

you can't do this
if you don't give a definition.

People always say: "Consciousness
is very hard to define."

I think it is rather easy to define

if you are not trying to give
a scientific definition.

We are not ready
for a scientific definition,

but here is the common sense definition:

consciousness consists of all those states
of feelings, or sensations, or awareness;

it begins in the morning
when you wake up from a dream,

and it goes on all day,
until you fall asleep, or die,

or otherwise become unconscious.

Dreams are a form
of consciousness on this definition.

That's the common sense definition,
that's our target;

if you are not talking about that,
you are not talking about consciousness.

But they think:"Well, that's it!

That's an awful problem!

How can such thing exist
as part of the real world?"

And this, if you have ever had
a philosophy course,

this is known
as the famous "mind-body problem."

I think that has a simple solution to it
and I am going to give it to you.

And here it is:

all of our conscious states,
without exception, are caused

by lower-level neurobiological processes
in the brain.

And they are realized in the brain
as higher-level or system features.

It is about as mysterious
as the liquidity of water, right?

The liquidity is not an extra juice

squirted out by the H2O molecules,

it's a condition that the system is in.

And just as the jar full of water
can go from liquid to solid,

depending on the behavior
of the molecules,

so your brain can go
from a state of being conscious

to a state of being unconscious,

depending on the behavior
of the molecules.

The famous "mind-body problem"
is that simple.

But now, we get
into some harder questions.

Let's specify
the exact features of consciousness

so that we can then answer
those four objections that I made to it.

Well, the first feature is
it is real and irreducible.

You can't get rid of it.

You see, the distinction
between reality and illusion

is the distinction between how things
consciously seem to us

and how they really are.

If consciousness seems like...

I like the French "arch",
it seems like there's an arch in the sky,

or it seems like the sun
is setting over the mountains,

it consciously seems to us

but that's not really happening.

But for that distinction,

between how things consciously seem
and how they really are,

you can't make that distinction
for the very existence of consciousness.

Because we are
the very existence of consciousness:

if it consciously seems to you,
that you are conscious,

you are conscious!

(Laughter)

I mean if a bunch of experts
come to me and say:

"We are heavy-duty neurobiologists
and we've done a study on you Searle,"

and we are convinced
you are not conscious.

You're a very cleverly constructed robot."

I don't think: " Well, maybe
these guys are right!"

I don't think that for a moment!

Because, I mean, Descartes
may have made a lot of mistakes

but he is right about this:

you cannot doubt the existence
of your own consciousness.

That's the first feature of consciousness.

It is real and irreducible.

You cannot get rid of it
by showing that it's an illusion,

in a way that you can
with other standard illusions.

The second feature is this one

that has been such a source
of trouble to us.

And that is all of our conscious states

have this qualitative character to them;

there is something
that it feels like to drink beer,

which is not what feels like
to do your income tax,

or listen to music.

And this qualitative field
automatically generates a third feature,

namely, conscious states
are by definition subjective,

in the sense that they only exist

as experienced
by some human or animal subjects,

some self that experiences them.

Maybe we will be able
to build a conscious machine,

[but] since we don't know
how our brains do it,

we are not in the position, so far,
to build a conscious machine.

Okay, another feature of consciousness

is that it comes
in unified conscious fields.

I don't just have the sight
of people in front of me,

and the sound of my voice,

and the weight of my shoes
against the floor,

but they occur to me as part
of one single great conscious field

that stretches forward and backward.

That is the key to understanding
the enormous power of consciousness.

And we have not been able
to do that in a robot.

The disappointment of robotics
derives from the fact

that we don't know
how to make a conscious robot,

so we don't have a machine
that can do this kind of thing.

The next feature of consciousness

after this marvelous,
unified conscious field

is that it functions causally
in our behavior.

I gave you a scientific demonstration
by raising my hand,

but how is that possible?

How can it be
that this thought in my brain

can move material objects?

Well, I will tell you the answer.

--we don't know the detailed answer,

but we know the basic part of the answer--

and that is there are sequences
of neuron firings

and they terminate
where the acetylcholine is secreted

at the axon end-plates
of the motor neurons,

sorry to use
philosophical terminology here.

(Laughter)

But when it is secreted

at the axon end-plates
of the motor neurons,

a lot of wonderful things
happen in the ion channels

and the damned arm goes up.

And think of what I have told you.

One and the same event,

my conscious decision to raise my hand

has a level of description

where it has all of these touchy-feely,
spiritual qualities,

--it's a thought in my brain--

but at the same time,

it's busy secreting acetylcholine

and doing all sorts of other things

as it makes its way from the motor cortex

down through the nerves fibers
and the arm.

Now, what that tells us
is that our traditional vocabularies

for discussing these issues,
are totally obsolete!

One and the same event,

has a level of description
where's neurobiological,

and another level of description
where's mental,

and that's a single event

and that's how nature works,

that's how is possible
for consciousness to function causally.

Now, with that in mind,

with going through these various features
of consciousness,

let's go back and answer
some of those early objections.

Well, the first one I said,
was consciousness doesn't exist,

it's an illusion.

Well, I've already answered that

I don't think we need to worry about that.

But the second one,
had an incredible influence

and may still be around,
and that is

if consciousness exists,
it's really something else;

it's really a digital computer program

running in your brain,

and that's what we need to do
to create consciousness,

get the right program.

Forget about the hardware,
any hardware will do,

provided is rich enough and stable enough
to carry the program.

Now, we know that that's wrong.

I mean, anybody who's thought
about computers at all

can see that that's wrong.

Because computation is defined
as symbol manipulation,

usually thought as 0s and 1s,
but any symbols will do.

You get an algorithm

that you can program in a binary code

and that's the defining trait
of the computer program.

But we know that's purely syntactical,
that's symbolic,

we know that actual human consciousness

has something more than that,
it's got a content,

in addition to the syntax,
it's got a semantics.

I made that argument,

--oh, my god!
I don't want to think about it!--

more that 30 years ago,

but there is a deeper argument
implicit in what I've told you.

And I want to tell you that argument
briefly, and that is:

consciousness creates an observer
independent reality.

It creates a reality of money,
property, government,

marriage, CERN, conferences,

cocktail parties, and summer vacations.

And all of those
are creations of consciousness.

Their existence is observer-relative.

It's only relative to conscious agents;

that a piece of paper is a money,

or a bunch of buildings is a university.

Now, ask yourselves about computation.

Is that absolute?

Like force, and mass,
and gravitational attraction?

Or is it observer-relative?

Well, some computations are intrinsic.

I add two plus two to get four,

that's going on no matter
what anybody thinks.

But when I hold out my pocket calculator
and do the calculation,

the only intrinsic phenomenon

is the electronic circuit
and its behavior.

That's the only absolute phenomenon.

All the rest is interpreted by us.

Computation only exists
relative to consciousness.

Either a conscious agent
is carrying the computation

or it has a piece of machinery

that admits
of a computational interpretation.

That doesn't mean
computation is arbitrary,

I spent a lot of money
on this hardware,

but we have this persistent confusion

between objectivity and subjectivity

as features of reality,

and objectivity and subjectivity

as features of claims.

And the bottom line
of this part of my talk, is this:

you can have
a completely objective science,

a science where you make
objectively true claims

about a domain whose existence
is subjective,

whose existence is in the human brain,

consisting of subjective states
or sensations, or feeling, or awareness.

So the objection, that you can't have
an objective science of consciousness

because it's subjective,
and science is objective,

that's a pun, that's a bad pun
on objectivity and subjectivity.

You can make objective claims
about a domain that is subjective

in its mode of existence,

and indeed, that's what neurologists do.

You have patients
that actually suffered pains

and you are trying to get
an objective science of that.

I promised to refute all these guys,

but I don't have
an awful lot of time left,

but let me refute a couple more of them.

I said that behaviorism ought to be
one of the great embarrassments

of our intellectual culture,

because it's refuted the moment
you think about it.

Your mental states are identical
with your behavior?

Well, think about the distinction
between feeling a pain,

and engaging in pain behavior.

I mean, I won't demonstrate pain behavior

but I can tell you
I am not having any pains right now!

So it's an obvious mistake.

Why did they make the mistake?

The mistake was, and you go back

and ready the literature on this,
you can see this over and over,

they think [that] if you accept

the irreducible existence
of consciousness,

you're giving up on science,

you're giving up on 300 years

of human progress and human hope
and all the rest of it.

And the message
I want to leave you with is

consciousness has to become accepted
as a genuine biological phenomenon,

as much subject to scientific analysis

as any other phenomena in biology,
or, for that matter,

the rest of science!

Thank you very much.

(Applause)