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  • [APPLAUSE]

  • - Two out of the three fundamental mysteries

  • about our place in the universe have already been resolved.

  • The first is literally about our place in the universe.

  • Many years ago Copernicus told us that we were not at its

  • centre, that we were just a tiny dot suspended in the abyss.

  • This is an image of the earth taken from the probe Voyager 1

  • as it was leaving the solar system from about six

  • billion kilometres away.

  • All of human history, all of the history of life on Earth,

  • has taken place on that pale blue dot.

  • The second mystery, Darwin then revealed

  • that we humans are just one branch, or one twig,

  • of a beautifully rich and delicate evolutionary tree.

  • And that much of the machinery of life

  • is shared even with the lowliest of our fellow creatures.

  • The third mystery is that of consciousness,

  • our inner universe.

  • Now earlier this year, for the third time in my life,

  • I ceased to exist.

  • As the propofol anaesthetic flowed from the cannula

  • in my wrist into my bloodstream and then into my brain,

  • there was a falling apart.

  • A blackness.

  • An absence.

  • And then, I was back.

  • Drowsy and disoriented, but definitely there.

  • And when you wake from a deep sleep,

  • you might be confused what time it is, especially

  • in flying somewhere, but you'll know that some time has passed.

  • There seems to be some basic continuity

  • between your consciousness then, and your consciousness now.

  • But coming around from a general anaesthetic,

  • it could have been five minutes.

  • It could have been five hours.

  • It could have been five days, or five years.

  • I was simply not there.

  • A premonition of the oblivion of death.

  • And general anaesthesia doesn't just work on your brain.

  • It doesn't just work on your mind.

  • It works on your consciousness.

  • By altering the delicate electrochemical circuitry

  • inside your head, the basic ground state

  • of what it is to be is temporarily abolished.

  • And in this process lies one of the greatest remaining

  • mysteries in science and philosophy.

  • How does consciousness happen?

  • Why is life in the first person?

  • It is going away, and coming back.

  • The modern incarnation of this problem

  • is usually traced to Descartes, who in the 17th century

  • distinguished between matter stuff, res extensa, the stuff

  • that these desks are made of, that clothes are made of.

  • But also the brains and bodies and made of, material stuff.

  • And res cogitans, the stuff of thought, of feelings.

  • The stuff of consciousness.

  • And in making this distinction, he gave rise

  • to the now infamous mind/body problem,

  • and life has never been simple ever since.

  • But Descartes actually generated even more mischief

  • with his doctrine of the beast machine,

  • which I'm going to mention now, because it anticipates where

  • I'm going to end up as the bell rings when I finish in an hour.

  • Before Descartes, people commonly believed in something

  • called the great chain of being, with rocks and plants

  • at one end, and other non-human animals, a bit higher

  • up than humans, and then angels and gods at the very top.

  • And this great scale of being was also

  • a scale of moral virtue, so that humans had more moral virtues

  • than animals and plants, and then rocks and so on.

  • Now Descartes, in making this division between mind

  • and matter, argued that only humans had minds, and therefore

  • moral status, while other animals didn't have minds.

  • They were merely physiological machines, or beast machines,

  • morally equivalent to plants, and to rocks.

  • And in this view, the physiological mechanisms

  • that give rise to the property of being alive

  • were not relevant to the presence

  • of mind or consciousness.

  • Now I'm going to propose, at the end of this talk, the opposite.

  • That our conscious sense of self arises because of, and not

  • in spite of, the fact that we, too, are beast machines.

  • So to get there, let's return to the apparent mystery

  • of consciousness.

  • Now as recently as 1989, which is quite a while ago, but not

  • that long ago, Stuart Sutherland,

  • who was founding professor of experimental psychology

  • at my university of Sussex, had this to say.

  • "Consciousness is a fascinating but elusive phenomenon.

  • It is impossible to specify what it is, what it does,

  • or why it evolved.

  • Nothing worth reading has been written on it."

  • [LAUGHTER]

  • It's quite a pessimistic point of view.

  • And that may have been true then.

  • I don't think it was true then, but in any case

  • things have changed a lot since.

  • And more or less, about the time that Sutherland

  • made these remarks, we can see the birth, or the rebirth,

  • of the study of consciousness within the neurosciences.

  • And a good landmark is this paper

  • by Francis Crick and Christof Koch, published in 1990.

  • And they start their paper by saying that it is remarkable

  • that most of the work in cognitive sciences,

  • and the neurosciences, makes no reference to consciousness

  • or awareness at all.

  • And then they go on to propose their own theory

  • of what the neural correlates of consciousness are.

  • What it is in the brain that is responsible for being

  • conscious.

  • And since then, over the last 25 years,

  • there's been first a trickle, and now a deluge of research

  • on the brain basis of conscious experience.

  • Some of this work is being carried out

  • in my laboratory, the Sackler Centre, the consciousness

  • science, which was founded six years ago with Hugo

  • Critchley, my co-director.

  • And there are now even specialised academic journals,

  • The Neuroscience of Consciousness,

  • which I started last year with Oxford University Press.

  • And this is a real change of the tide.

  • When I started out more than 20 years ago,

  • it was thought to be a very-- it was thought

  • to be career suicide to want to study consciousness,

  • scientifically.

  • And it may still be, we don't know.

  • Let's see.

  • So while the brain basis of consciousness

  • is still a mystery, it is, in some sense,

  • an accessible mystery.

  • And the author, Mark Haddon, put this very nicely, I think.

  • He said the raw material of consciousness

  • is not on the other side of the universe.

  • It didn't happen 14 billion years ago.

  • And it's not squirrelled away deep inside an atom.

  • The raw material of consciousness

  • is right here, inside your head, and you can

  • hold the brain in your hands.

  • But the brain won't deliver its secrets very easily.

  • What's extraordinary about the brain

  • is not so much the number of neurons,

  • though there are about 90 billion.

  • It's not even the number of connections,

  • though there are so many that if you counted one every second,

  • it would take you about three million years

  • to finish counting.

  • What's truly extraordinary are the patterns

  • of connectivity, which to a large extent,

  • are still not known, but within which are inscribed everything

  • that makes you, you.

  • The challenge is then this, at least the the way I see it.

  • How can the structure and dynamics

  • of the brain, in connection with the body and the environment,

  • account for the subjective phenomenological properties

  • of consciousness?

  • And considering things this way, we

  • come up against what the philosopher David

  • Chalmers has often called the hard problem of consciousness.

  • And the idea is this.

  • There is an easy problem.

  • The easy problem is to understand how the combined

  • operations of the brain and the body give rise to perception,

  • to cognition, to thinking, to learning, to behaviour.

  • How the brain works, in other words.

  • The hard problem is to understand

  • why and how any of this should have anything

  • to do with consciousness at all.

  • Why aren't we just robots, or philosophical zombies,

  • without any in a universe?

  • Now there's a tempting intuition here,

  • which is that, even if we solve the hard problem, even if we

  • solve the easy problem, the hard problem would still remain

  • as mysterious as it seems now.

  • But this just seems wrong-headed to me.

  • It may not be necessary to explain why consciousness

  • exists at all, in order to make progress in understanding

  • its material basis.

  • And this for me, is the real problem of consciousness;

  • how to account for its various properties in terms

  • of biological mechanisms without pretending that it doesn't

  • exist at all, as you do if you solve the easy problem,

  • and without trying to account for why it's

  • parts of the universe in the first place, which

  • is the hard problem.

  • And in the history of science, we've

  • been somewhere similar before.

  • It's hard to say if it's exactly the same situation.

  • But in our understanding of life,

  • eminent biochemists of the time found it entirely mysterious

  • how biological mechanisms could give rise

  • to the property of being alive.

  • And there were proposed of things,

  • like elan vital and essence vital,

  • and all sorts of other stuff.

  • And although we don't yet understand everything

  • about life, this initial sense of mystery about life

  • has, to a large extent, dissolved

  • as biologists have just got on with the business

  • of understanding the properties of living systems in terms

  • of mechanisms.

  • An important part of this story was

  • the realisation that life is not just one thing,

  • but rather a constellation of partially dependent, partially

  • separable, processes, like metabolism, homeostasis,

  • and reproduction.

  • In the same way, to make progress

  • on the real problem of consciousness,

  • it can be useful to distinguish different aspects or dimensions

  • of what it is to be conscious.

  • The space of possible minds, if you like.

  • And one simple classification is into conscious level,

  • which is the property of being conscious at all.

  • For example, the difference between being

  • in a dreamless sleep, or under general anaesthesia,

  • and being awake and conscious as you are now.

  • And the conscious content, when you are conscious,

  • you're conscious of something.

  • The myriad of sights, sounds, smells, emotions, feelings,

  • and beliefs that populate your inner universe at any one time.

  • And one thing you are conscious of when you are conscious,

  • is the experience, the specific experience, of being you,

  • and this is conscious self.

  • And it's the third dimension of consciousness.

  • Now I don't claim these distinctions mark

  • completely independent aspects of what it is to be conscious,

  • but they're a pragmatically useful way of breaking down

  • the problem a bit.

  • So let's start with conscious level.

  • What are the fundamental brain mechanisms

  • that underlie our ability to be conscious at all?

  • And we can think of this, at least a first approximation,

  • as a scale from being completely unconscious,

  • as if you were in a coma, or under general anaesthesia,

  • to being awake, alert, and fully conscious as you are now.

  • And there's various states in between being drowsy,

  • being mildly sedated and so on.

  • What's important is that, while being conscious and being awake

  • often go together, this is not always the case.

  • For instance, when you are dreaming you are asleep,

  • but you are having conscious experiences.

  • The conscious experience of your dreams.

  • And on the other side of this diagram,

  • there are pathological states, like the vegetative state,

  • where physiologically you will go through sleep/wake cycles,

  • but there is nobody at home.

  • There is no consciousness happening.

  • So what are the specific mechanisms