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I'm going to talk about consciousness.
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Why consciousness?
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Well, it's a curiously neglected subjected,
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both in our scientific and our philosophical culture.
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Now why is that curious?
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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 conscious is number one.
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The second reason is that when people do
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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,
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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 UCFS 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,
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a very famous neurobiologist, he said, "Look,
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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 damnful thing,
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but in any case it's not part of science.
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And I used to get 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, you know,
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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.
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(Laughter) (Applause)
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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 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,
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there are a sequence of neuron firings,
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and they terminate where the acetylcholine
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is secreted at the axon end plates of the motor neurons.
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Sorry to use philosophical terminology here,
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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
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for discussing these issues are totally obsolete.
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One and the same event has a level of description
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where it's neurobiological, and another level of description
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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
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for consciousness to function causally.
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Okay, now with that in mind,
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with going through these various features of consciousness,
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let's go back and answer some of those early objections.
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Well, the first one I said was consciousness doesn't exist,
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it's an illusion. Well, I've already answered that.
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I don't think we need to worry about that.
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But the second one had an incredible influence,
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and may still be around, and that is,
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"Well, if consciousness exists, it's really something else.
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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
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is get the right program.
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Yeah, forget about the hardware. Any hardware will do
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provided it's rich enough and stable enough to carry the program."
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Now, we know that that's wrong.
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I mean, anybody who's thought about computers at all
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can see that that's wrong, because computation
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is defined as symbol manipulation,
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usually thought of as zeros as ones, but any symbols will do.
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You get an algorithm that you can program
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in a binary code, and that's the defining trait
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of the computer program.
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But we know that that's purely syntactical. That's symbolic.
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We know that actual human consciousness has something more than that.
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It's got a content in addition to the syntax.
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It's got a semantics.
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Now that argument, I made that argument 30
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— oh my God, I don't want to think about it —
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more than 30 years ago,
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but there's a deeper argument implicit in what I've told you,
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and I want to tell you that argument briefly, and that is,
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consciousness creates an observer-independent reality.
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It creates a reality of money, property, government,
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marriage, CERN conferences,
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cocktail parties and summer vacations,
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and all of those are creations of consciousness.
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Their existence is observer-relative.
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It's only relative to conscious agents that a piece of paper
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is money or that a bunch of buildings is a university.
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Now, ask yourself about computation.
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Is that absolute, like force and mass and gravitational attraction?
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Or is it observer-relative?
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Well, some computations are intrinsic.
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I add two plus two to get four.
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That's going on no matter what anybody thinks.
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But when I haul out my pocket calculator
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and do the calculation, the only intrinsic phenomenon
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is the electronic circuit and its behavior.
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That's the only absolute phenomenon.
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All the rest is interpreted by us.
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Computation only exists relative to consciousness.
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Either a conscious agent is carrying out the computation,
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or he's got a piece of machinery that admits of a computational interpretation.
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Now that doesn't mean computation is arbitrary.
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I spent a lot of money on this hardware.
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But we have this persistent confusion
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between objectivity and subjectivity as features of reality
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and objectivity and subjectivity as features of claims.
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And the bottom line of this part of my talk is this:
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you can have a completely objective science,
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a science where you make objectively true claims,
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about a domain whose existence is subjective,
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whose existence is in the human brain
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consisting of subjective states of sentience
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or feeling or awareness.
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So the objection that you can't have an objective science of consciousness
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because it's subjective and science is objective, that's a pun.
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That's a bad pun on objectivity and subjectivity.
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You can make objective claims
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about a domain that is subjective in its mode of existence,
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and indeed that's what neurologists do.
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I mean, you have patients that actually suffer pains,
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and you try to get an objective science of that.
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Okay, I promised to refute all these guys,
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and I don't have an awful lot of time left,
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but let me refute a couple more of them.
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I said that behaviorism ought to be
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one of the great embarrassments of our intellectual culture,
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because it's refuted the moment you think about it.
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Your mental states are identical with your behavior?
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Well, think about the distinction between feeling a pain
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and engaging in pain behavior.
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I won't demonstrate pain behavior, but I can tell you
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I'm not having any pains right now.
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So it's an obvious mistake. Why did they make the mistake?
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The mistake was — and you can go back and read
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the literature on this, you can see this over and over —
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they think if you accept the irreducible existence
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of consciousness, you're giving up on science.
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You're giving up on 300 years of human progress
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and human hope and all the rest of it.
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And the message I want to leave you with is,
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consciousness has to become accepted
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as a genuine biological phenomenon,
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as much subject to scientific analysis
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as any other phenomenon in biology,
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or, for that matter, the rest of science.
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Thank you very much.
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(Applause)