0:00:00.000,0:00:03.000
I'm going to talk about consciousness.

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Why consciousness?

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Well, it's a curiously neglected subject,

0:00:07.000,0:00:10.000
both in our scientific and our philosophical culture.

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Now why is that curious?

0:00:12.000,0:00:15.000
Well, it is the most important aspect of our lives

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for a very simple, logical reason,

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namely, it's a necessary condition on anything

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being important in our lives that we're conscious.

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You care about science, philosophy, music, art, whatever --

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it's no good if you're a zombie or in a coma, right?

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So consciousness is number one.

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The second reason is that when people do

0:00:34.000,0:00:36.000
get interested in it, as I think they should,

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they tend to say the most appalling things.

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And then, even when they're not saying appalling things

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and they're really trying to do serious research,

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

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When I first got interested in this, I thought, well,

0:00:50.000,0:00:52.000
it's a straightforward problem in biology.

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Let's get these brain stabbers to get busy and figure out

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how it works in the brain.

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So I went over to UCSF and I talked to all

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the heavy-duty neurobiologists there,

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and they showed some impatience,

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as scientists often do when you ask them embarrassing questions.

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But the thing that struck me is, one guy said in exasperation,

0:01:08.000,0:01:10.000
a very famous neurobiologist, he said, "Look,

0:01:10.000,0:01:14.000
in my discipline it's okay to be interested in consciousness,

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but get tenure first. Get tenure first."

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Now I've been working on this for a long time.

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I think now you might actually get tenure

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by working on consciousness.

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If so, that's a real step forward.

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Okay, now why then is this curious reluctance

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and curious hostility to consciousness.

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Well, I think it's a combination of two features

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of our intellectual culture

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that like to think they're opposing each other

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but in fact they share a common set of assumptions.

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One feature is the tradition of religious dualism:

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Consciousness is not a part of the physical world.

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It's a part of the spiritual world.

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It belongs to the soul,

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

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

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There's another tradition that thinks it's opposed to this

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but accepts the worst assumption.

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That tradition thinks that we are heavy-duty scientific materialists:

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Consciousness is not a part of the physical world.

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Either it doesn't exist at all, or it's something else,

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a computer program or some damn fool thing,

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but in any case it's not part of science.

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

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Here's how it went.

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Science is objective, consciousness is subjective,

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therefore there cannot be a science of consciousness.

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Okay, so these twin traditions are paralyzing us.

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It's very hard to get out of these twin traditions.

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And I have only one real message in this lecture,

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and that is, consciousness is a biological phenomenon

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like photosynthesis, digestion, mitosis --

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you know all the biological phenomena -- and once you accept that,

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most, though not all, of the hard problems

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about consciousness simply evaporate.

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And I'm going to go through some of them.

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Okay, now I promised you to tell you some

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of the outrageous things said about consciousness.

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One: Consciousness does not exist.

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It's an illusion, like sunsets.

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Science has shown sunsets and rainbows are illusions.

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So consciousness is an illusion.

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Two: Well, maybe it exists, but it's really something else.

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It's a computer program running in the brain.

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

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It's embarrassing how influential behaviorism was,

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but I'll get back to that.

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And four: Maybe consciousness exists,

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

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How could spirituality move anything?

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Now, whenever somebody tells me that, I think,

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you want to see spirituality move something?

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Watch. I decide consciously to raise my arm,

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and the damn thing goes up. (Laughter)

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Furthermore, notice this:

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We do not say, "Well, it's a bit like the weather in Geneva.

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

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No. It goes up whenever I damn well want it to.

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Okay. I'm going to tell you how that's possible.

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

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

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People always say consciousness is very hard to define.

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I think it's rather easy to define

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if you're not trying to give a scientific definition.

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We're not ready for a scientific definition,

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but here's a commonsense definition.

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Consciousness consists of all those states of feeling

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or sentience or awareness.

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It begins in the morning when you wake up from a dreamless sleep,

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and it goes on all day until you fall asleep

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or die or otherwise become unconscious.

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Dreams are a form of consciousness on this definition.

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Now, that's the commonsense definition. That's our target.

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If you're not talking about that, you're not talking about consciousness.

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But they think, "Well, if that's it, that's an awful problem.

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

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And this, if you've ever had a philosophy course,

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this is known as the famous mind-body problem.

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I think that has a simple solution too. I'm going to give it to you.

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And here it is: All of our conscious states, without exception,

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are caused by lower-level neurobiological processes in the brain,

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and they are realized in the brain

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as higher-level or system features.

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It's about as mysterious as the liquidity of water.

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Right? The liquidity is not an extra juice squirted out

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by the H2O molecules.

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It's a condition that the system is in.

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

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depending on the behavior of the molecules,

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so your brain can go from a state of being conscious

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to a state of being unconscious,

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depending on the behavior of the molecules.

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The famous mind-body problem is that simple.

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All right? But now we get into some harder questions.

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Let's specify the exact features of consciousness,

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so that we can then answer those four objections

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that I made to it.

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

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You can't get rid of it.

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You see, the distinction between reality and illusion

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is the distinction between how things

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consciously seem to us and how they really are.

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It consciously seems like there's --

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I like the French "arc-en-ciel" —

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

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

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It consciously seems to us, but that's not really happening.

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But for that distinction between

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how things consciously seem and how they really are,

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

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because where the very existence of consciousness is concerned,

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if it consciously seems to you that you are conscious,

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you are conscious.

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

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"We are heavy-duty neurobiologists and we've done a study

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of you, Searle, and we're convinced you are not conscious,

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you are a very cleverly constructed robot,"

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I don't think, "Well, maybe these guys are right, you know?"

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I don't think that for a moment, because, I mean,

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Descartes may have made a lot of mistakes, but he was right about this.

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You cannot doubt the existence of your own consciousness.

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Okay, that's the first feature of consciousness.

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It's real and irreducible.

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

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in a way that you can with other standard illusions.

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Okay, the second feature is this one

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that has been such a source of trouble to us,

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and that is, all of our conscious states

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have this qualitative character to them.

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There's something that it feels like to drink beer

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

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or listen to music, and this qualitative feel

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automatically generates a third feature,

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namely, conscious states are by definition subjective

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in the sense that they only exist as experienced

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by some human or animal subject,

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some self that experiences them.

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Maybe we'll be able to build a conscious machine.

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Since we don't know how our brains do it,

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we're not in a position, so far, to build a conscious machine.

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Okay. Another feature of consciousness

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is that it comes in unified conscious fields.

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

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and the sound of my voice and the weight of my shoes

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against the floor, but they occur to me

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as part of one single great conscious field

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that stretches forward and backward.

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That is the key to understanding

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the enormous power of consciousness.

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

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The disappointment of robotics derives from the fact

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

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

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Okay, the next feature of consciousness,

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after this marvelous unified conscious field,

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is that it functions causally in our behavior.

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I gave you a scientific demonstration by raising my hand,

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but how is that possible?

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How can it be that this thought in my brain

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can move material objects?

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Well, I'll tell you the answer.

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I mean, we don't know the detailed answer,

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but we know the basic part of the answer, and that is,

0:08:59.000,0:09:01.000
there are a sequence of neuron firings,

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and they terminate where the acetylcholine

0:09:04.000,0:09:07.000
is secreted at the axon end-plates of the motor neurons.

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Sorry to use philosophical terminology here,

0:09:09.000,0:09:13.000
but when it's secreted at the axon end-plates of the motor neurons,

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a whole lot of wonderful things happen in the ion channels

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and the damned arm goes up.

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Now, think of what I told you.

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One and the same event,

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my conscious decision to raise my arm

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has a level of description where it has all of these

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touchy-feely spiritual qualities.

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It's a thought in my brain, but at the same time,

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it's busy secreting acetylcholine

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and doing all sorts of other things

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as it makes its way from the motor cortex

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down through the nerve fibers in the arm.

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Now, what that tells us is that our traditional vocabularies

0:09:45.000,0:09:48.000
for discussing these issues are totally obsolete.

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One and the same event has a level of description

0:09:51.000,0:09:54.000
where it's neurobiological, and another level of description

0:09:54.000,0:09:57.000
where it's mental, and that's a single event,

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and that's how nature works. That's how it's possible

0:09:59.000,0:10:02.000
for consciousness to function causally.

0:10:02.000,0:10:05.000
Okay, now with that in mind,

0:10:05.000,0:10:08.000
with going through these various features of consciousness,

0:10:08.000,0:10:11.000
let's go back and answer some of those early objections.

0:10:11.000,0:10:14.000
Well, the first one I said was, consciousness doesn't exist,

0:10:14.000,0:10:16.000
it's an illusion. Well, I've already answered that.

0:10:16.000,0:10:18.000
I don't think we need to worry about that.

0:10:18.000,0:10:22.000
But the second one had an incredible influence,

0:10:22.000,0:10:23.000
and may still be around, and that is,

0:10:23.000,0:10:27.000
"Well, if consciousness exists, it's really something else.

0:10:27.000,0:10:30.000
It's really a digital computer program running in your brain

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

0:10:33.000,0:10:34.000
is get the right program.

0:10:34.000,0:10:37.000
Yeah, forget about the hardware. Any hardware will do

0:10:37.000,0:10:40.000
provided it's rich enough and stable enough to carry the program."

0:10:40.000,0:10:43.000
Now, we know that that's wrong.

0:10:43.000,0:10:46.000
I mean, anybody who's thought about computers at all

0:10:46.000,0:10:48.000
can see that that's wrong, because computation

0:10:48.000,0:10:51.000
is defined as symbol manipulation,

0:10:51.000,0:10:53.000
usually thought of as zeros as ones, but any symbols will do.

0:10:53.000,0:10:57.000
You get an algorithm that you can program

0:10:57.000,0:11:00.000
in a binary code, and that's the defining trait

0:11:00.000,0:11:02.000
of the computer program.

0:11:02.000,0:11:06.000
But we know that that's purely syntactical. That's symbolic.

0:11:06.000,0:11:10.000
We know that actual human consciousness has something more than that.

0:11:10.000,0:11:13.000
It's got a content in addition to the syntax.

0:11:13.000,0:11:14.000
It's got a semantics.

0:11:14.000,0:11:17.000
Now that argument, I made that argument 30 --

0:11:17.000,0:11:18.000
oh my God, I don't want to think about it —

0:11:18.000,0:11:19.000
more than 30 years ago,

0:11:19.000,0:11:22.000
but there's a deeper argument implicit in what I've told you,

0:11:22.000,0:11:25.000
and I want to tell you that argument briefly, and that is,

0:11:25.000,0:11:30.000
consciousness creates an observer-independent reality.

0:11:30.000,0:11:33.000
It creates a reality of money, property, government,

0:11:33.000,0:11:37.000
marriage, CERN conferences,

0:11:37.000,0:11:40.000
cocktail parties and summer vacations,

0:11:40.000,0:11:42.000
and all of those are creations of consciousness.

0:11:42.000,0:11:45.000
Their existence is observer-relative.

0:11:45.000,0:11:49.000
It's only relative to conscious agents that a piece of paper

0:11:49.000,0:11:52.000
is money or that a bunch of buildings is a university.

0:11:52.000,0:11:55.000
Now, ask yourself about computation.

0:11:55.000,0:11:59.000
Is that absolute, like force and mass and gravitational attraction?

0:11:59.000,0:12:01.000
Or is it observer-relative?

0:12:01.000,0:12:05.000
Well, some computations are intrinsic.

0:12:05.000,0:12:07.000
I add two plus two to get four.

0:12:07.000,0:12:09.000
That's going on no matter what anybody thinks.

0:12:09.000,0:12:12.000
But when I haul out my pocket calculator

0:12:12.000,0:12:16.000
and do the calculation, the only intrinsic phenomenon

0:12:16.000,0:12:19.000
is the electronic circuit and its behavior.

0:12:19.000,0:12:21.000
That's the only absolute phenomenon.

0:12:21.000,0:12:23.000
All the rest is interpreted by us.

0:12:23.000,0:12:27.000
Computation only exists relative to consciousness.

0:12:27.000,0:12:30.000
Either a conscious agent is carrying out the computation,

0:12:30.000,0:12:33.000
or he's got a piece of machinery that admits of a computational interpretation.

0:12:33.000,0:12:36.000
Now that doesn't mean computation is arbitrary.

0:12:36.000,0:12:39.000
I spent a lot of money on this hardware.

0:12:39.000,0:12:41.000
But we have this persistent confusion

0:12:41.000,0:12:46.000
between objectivity and subjectivity as features of reality

0:12:46.000,0:12:49.000
and objectivity and subjectivity as features of claims.

0:12:49.000,0:12:53.000
And the bottom line of this part of my talk is this:

0:12:53.000,0:12:56.000
You can have a completely objective science,

0:12:56.000,0:12:59.000
a science where you make objectively true claims,

0:12:59.000,0:13:03.000
about a domain whose existence is subjective,

0:13:03.000,0:13:06.000
whose existence is in the human brain

0:13:06.000,0:13:08.000
consisting of subjective states of sentience

0:13:08.000,0:13:10.000
or feeling or awareness.

0:13:10.000,0:13:14.000
So the objection that you can't have an objective science of consciousness

0:13:14.000,0:13:18.000
because it's subjective and science is objective, that's a pun.

0:13:18.000,0:13:21.000
That's a bad pun on objectivity and subjectivity.

0:13:21.000,0:13:23.000
You can make objective claims

0:13:23.000,0:13:27.000
about a domain that is subjective in its mode of existence,

0:13:27.000,0:13:29.000
and indeed that's what neurologists do.

0:13:29.000,0:13:31.000
I mean, you have patients that actually suffer pains,

0:13:31.000,0:13:34.000
and you try to get an objective science of that.

0:13:34.000,0:13:36.000
Okay, I promised to refute all these guys,

0:13:36.000,0:13:38.000
and I don't have an awful lot of time left,

0:13:38.000,0:13:40.000
but let me refute a couple more of them.

0:13:40.000,0:13:42.000
I said that behaviorism ought to be

0:13:42.000,0:13:45.000
one of the great embarrassments of our intellectual culture,

0:13:45.000,0:13:48.000
because it's refuted the moment you think about it.

0:13:48.000,0:13:51.000
Your mental states are identical with your behavior?

0:13:51.000,0:13:54.000
Well, think about the distinction between feeling a pain

0:13:54.000,0:13:56.000
and engaging in pain behavior.

0:13:56.000,0:13:58.000
I won't demonstrate pain behavior, but I can tell you

0:13:58.000,0:14:00.000
I'm not having any pains right now.

0:14:00.000,0:14:04.000
So it's an obvious mistake. Why did they make the mistake?

0:14:04.000,0:14:06.000
The mistake was — and you can go back and read

0:14:06.000,0:14:08.000
the literature on this, you can see this over and over —

0:14:08.000,0:14:12.000
they think if you accept the irreducible existence

0:14:12.000,0:14:15.000
of consciousness, you're giving up on science.

0:14:15.000,0:14:18.000
You're giving up on 300 years of human progress

0:14:18.000,0:14:20.000
and human hope and all the rest of it.

0:14:20.000,0:14:23.000
And the message I want to leave you with is,

0:14:23.000,0:14:25.000
consciousness has to become accepted

0:14:25.000,0:14:28.000
as a genuine biological phenomenon,

0:14:28.000,0:14:30.000
as much subject to scientific analysis

0:14:30.000,0:14:32.000
as any other phenomenon in biology,

0:14:32.000,0:14:34.000
or, for that matter, the rest of science.

0:14:34.000,0:14:36.000
Thank you very much.

0:14:36.000,0:14:41.000
(Applause)