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← Consciousness and the brain | John Searle | TEDxCERN

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Showing Revision 42 created 11/16/2014 by Denise RQ.

  1. I am going to talk about consciousness.
  2. Why consciousness?
  3. It is curiously a neglected subject
  4. both in our scientific
    and our philosophical culture.
  5. Why is that curious?
  6. It's most important aspect of our lives
    for a very simple logical reason,
  7. namely, it is a necessary condition
    on anything being important in our lives
  8. that we are conscious.
  9. [If] you care about science,
    philosophy, music, art, whatever,
  10. it is no good if you are
    a zombie or in a coma, right?
  11. So consciousness is number one.
  12. That's the first reason
    [that] we are talking about it.
  13. The second reason is that when people
    do get interested in it,
  14. as I think they should,
  15. they tend to say
    the most appalling things!
  16. I am not going to attempt
    to conceal from you
  17. some of the most appalling things
    that have been said about it;
  18. and even when they are not saying
    appalling things
  19. [and] they are really trying
    to do serious research,
  20. well, it's been slow,
    progress has been slow.
  21. Let me tell you a little bit
    about some of the difficulties.
  22. When I first got interested
    in this, I thought
  23. it's a straightforward problem in biology
  24. [so] let's get these brain stabbers
    to get busy
  25. and figure out how it works in the brain.
  26. I went over to UCSF and talked
    to all heavy-duty neurologists there
  27. and they showed some impatience,
  28. as scientists often do when you ask them
    embarrassing questions,
  29. and the thing that struck me
  30. is that a very famous neurobiologist
    said exasperated:
  31. "Look, in my discipline,
    it's OK to be interested in consciousness,
  32. but get tenure first!
  33. (Laughter)
  34. I've been working on this for a long time
  35. and now you might actually get tenure
  36. by working on consciousness,
    and if so, that's a real step forward!
  37. Why then, is this curious reluctance
  38. and curious hostility to consciousness?
  39. I think it's a combination of two features
    of our intellectual culture
  40. that like to think
    they are opposing each other
  41. but in fact they share
    a common set of assumptions.
  42. Consciousness is not a part
    of the physical world
  43. but it's part of the spiritual world,
    it belongs to the soul,
  44. and the soul is not a part
    of the physical world.
  45. That's the tradition of God,
    the soul, and immortality.
  46. There is another tradition
    that is opposed to this
  47. but excepts the worst assumption.
  48. That tradition thinks
    we are heavy-duty scientific materialists,
  49. consciousness is not a part
    of the physical world,
  50. either it doesn't exist at all
    or it is something else,
  51. a computer program
    or some damn fool thing.
  52. (Laughter)
  53. But in any case, it's not part of science!
  54. I used to get in an argument
    that really gave me a stomachache.
  55. Here is how it went:
  56. "Science is objective,
    consciousness is subjective,
  57. therefore, there cannot be
    a science of consciousness."
  58. I love that argument
  59. because it has got
    a wonderful fallacy of ambiguity
  60. over the concept of objectivity.
  61. And I have already used up too much time
  62. just to clearing my breath,
    sort of speak,
  63. but I want to get to that.
  64. These twin traditions are paralyzing us,
  65. and it's very hard to get out
    of these twin traditions,
  66. and I have only one real message
    in this lecture,
  67. and that is consciousness
  68. is a biological phenomenon,
    like photosynthesis,
  69. digestion, mitosis,
    and all that biological phenomena.
  70. And once you accept that,
  71. most, though not all,
  72. of the hard problems about consciousness
  73. simply evaporate!
  74. And I will go through some of them.
  75. I promised you to tell you
  76. some of the outrageous things
    said about consciousness,
  77. and because of shortage of time,
    I will only mention four of the worst.
  78. One: "Consciousness does not exist.
  79. It is an illusion, like sunsets."
  80. Science has shown sunsets
    and rainbows are illusions,
  81. so consciousness is an illusion.
  82. Two: "Maybe it exists,
    but it is really something else,
  83. it's a computer program
    running in the brain."
  84. Three: "No, the only thing
    that exists is really behavior!"
  85. It's embarrassing
    how influential behaviorism was,
  86. but I will get back to that.
  87. Four: "Maybe consciousness exists,
  88. but it can't make
    any difference to the world.
  89. How could spirituality move anything?"
  90. And whenever somebody
    tells me that, I think:
  91. "You want to see if spirituality
    moves something? Watch!"
  92. I decide consciously to raise my arm
    and the damn thing goes up.
  93. (Laughter)
  94. (Applause)
  95. Furthermore, we do not say:
    "It's a bit like the weather in Geneva,
  96. some days it goes up
    and some days it doesn't go up."
  97. No! It goes up
  98. when I right damn well want it to!
  99. I will tell you how that is possible.
  100. Now, I haven't yet given you a definition,
  101. you can't do this
    if you don't give a definition.
  102. People always say: "Consciousness
    is very hard to define."
  103. I think it is rather easy to define
  104. if you are not trying to give
    a scientific definition.
  105. We are not ready
    for a scientific definition,
  106. but here is the common sense definition:
  107. consciousness consists of all those states
    of feelings, or sensations, or awareness;
  108. it begins in the morning
    when you wake up from a dream,
  109. and it goes on all day,
    until you fall asleep, or die,
  110. or otherwise become unconscious.
  111. Dreams are a form
    of consciousness on this definition.
  112. That's the common sense definition,
    that's our target;
  113. if you are not talking about that,
    you are not talking about consciousness.
  114. But they think:"Well, that's it!
  115. That's an awful problem!
  116. How can such thing exist
    as part of the real world?"
  117. And this, if you have ever had
    a philosophy course,
  118. this is known
    as the famous "mind-body problem."
  119. I think that has a simple solution to it
    and I am going to give it to you.
  120. And here it is:
  121. all of our conscious states,
    without exception, are caused
  122. by lower-level neurobiological processes
    in the brain.
  123. And they are realized in the brain
    as higher-level or system features.
  124. It is about as mysterious
    as the liquidity of water, right?
  125. The liquidity is not an extra juice
  126. squirted out by the H2O molecules,
  127. it's a condition that the system is in.
  128. And just as the jar full of water
    can go from liquid to solid,
  129. depending on the behavior
    of the molecules,
  130. so your brain can go
    from a state of being conscious
  131. to a state of being unconscious,
  132. depending on the behavior
    of the molecules.
  133. The famous "mind-body problem"
    is that simple.
  134. But now, we get
    into some harder questions.
  135. Let's specify
    the exact features of consciousness
  136. so that we can then answer
    those four objections that I made to it.
  137. Well, the first feature is
    it is real and irreducible.
  138. You can't get rid of it.
  139. You see, the distinction
    between reality and illusion
  140. is the distinction between how things
    consciously seem to us
  141. and how they really are.
  142. If consciousness seems like...
  143. I like the French "arch",
    it seems like there's an arch in the sky,
  144. or it seems like the sun
    is setting over the mountains,
  145. it consciously seems to us
  146. but that's not really happening.
  147. But for that distinction,
  148. between how things consciously seem
    and how they really are,
  149. you can't make that distinction
    for the very existence of consciousness.
  150. Because we are
    the very existence of consciousness:
  151. if it consciously seems to you,
    that you are conscious,
  152. you are conscious!
  153. (Laughter)
  154. I mean if a bunch of experts
    come to me and say:
  155. "We are heavy-duty neurobiologists
    and we've done a study on you Searle,"
  156. and we are convinced
    you are not conscious.
  157. You're a very cleverly constructed robot."
  158. I don't think: " Well, maybe
    these guys are right!"
  159. I don't think that for a moment!
  160. Because, I mean, Descartes
    may have made a lot of mistakes
  161. but he is right about this:
  162. you cannot doubt the existence
    of your own consciousness.
  163. That's the first feature of consciousness.
  164. It is real and irreducible.
  165. You cannot get rid of it
    by showing that it's an illusion,
  166. in a way that you can
    with other standard illusions.
  167. The second feature is this one
  168. that has been such a source
    of trouble to us.
  169. And that is all of our conscious states
  170. have this qualitative character to them;
  171. there is something
    that it feels like to drink beer,
  172. which is not what feels like
    to do your income tax,
  173. or listen to music.
  174. And this qualitative field
    automatically generates a third feature,
  175. namely, conscious states
    are by definition subjective,
  176. in the sense that they only exist
  177. as experienced
    by some human or animal subjects,
  178. some self that experiences them.
  179. Maybe we will be able
    to build a conscious machine,
  180. [but] since we don't know
    how our brains do it,
  181. we are not in the position, so far,
    to build a conscious machine.
  182. Okay, another feature of consciousness
  183. is that it comes
    in unified conscious fields.
  184. I don't just have the sight
    of people in front of me,
  185. and the sound of my voice,
  186. and the weight of my shoes
    against the floor,
  187. but they occur to me as part
    of one single great conscious field
  188. that stretches forward and backward.
  189. That is the key to understanding
    the enormous power of consciousness.
  190. And we have not been able
    to do that in a robot.
  191. The disappointment of robotics
    derives from the fact
  192. that we don't know
    how to make a conscious robot,
  193. so we don't have a machine
    that can do this kind of thing.
  194. The next feature of consciousness
  195. after this marvelous,
    unified conscious field
  196. is that it functions causally
    in our behavior.
  197. I gave you a scientific demonstration
    by raising my hand,
  198. but how is that possible?
  199. How can it be
    that this thought in my brain
  200. can move material objects?
  201. Well, I will tell you the answer.
  202. --we don't know the detailed answer,
  203. but we know the basic part of the answer--
  204. and that is there are sequences
    of neuron firings
  205. and they terminate
    where the acetylcholine is secreted
  206. at the axon end-plates
    of the motor neurons,
  207. sorry to use
    philosophical terminology here.
  208. (Laughter)
  209. But when it is secreted
  210. at the axon end-plates
    of the motor neurons,
  211. a lot of wonderful things
    happen in the ion channels
  212. and the damned arm goes up.
  213. And think of what I have told you.
  214. One and the same event,
  215. my conscious decision to raise my hand
  216. has a level of description
  217. where it has all of these touchy-feely,
    spiritual qualities,
  218. --it's a thought in my brain--
  219. but at the same time,
  220. it's busy secreting acetylcholine
  221. and doing all sorts of other things
  222. as it makes its way from the motor cortex
  223. down through the nerves fibers
    and the arm.
  224. Now, what that tells us
    is that our traditional vocabularies
  225. for discussing these issues,
    are totally obsolete!
  226. One and the same event,
  227. has a level of description
    where's neurobiological,
  228. and another level of description
    where's mental,
  229. and that's a single event
  230. and that's how nature works,
  231. that's how is possible
    for consciousness to function causally.
  232. Now, with that in mind,
  233. with going through these various features
    of consciousness,
  234. let's go back and answer
    some of those early objections.
  235. Well, the first one I said,
    was consciousness doesn't exist,
  236. it's an illusion.
  237. Well, I've already answered that
  238. I don't think we need to worry about that.
  239. But the second one,
    had an incredible influence
  240. and may still be around,
    and that is
  241. if consciousness exists,
    it's really something else;
  242. it's really a digital computer program
  243. running in your brain,
  244. and that's what we need to do
    to create consciousness,
  245. get the right program.
  246. Forget about the hardware,
    any hardware will do,
  247. provided is rich enough and stable enough
    to carry the program.
  248. Now, we know that that's wrong.
  249. I mean, anybody who's thought
    about computers at all
  250. can see that that's wrong.
  251. Because computation is defined
    as symbol manipulation,
  252. usually thought as 0s and 1s,
    but any symbols will do.
  253. You get an algorithm
  254. that you can program in a binary code
  255. and that's the defining trait
    of the computer program.
  256. But we know that's purely syntactical,
    that's symbolic,
  257. we know that actual human consciousness
  258. has something more than that,
    it's got a content,
  259. in addition to the syntax,
    it's got a semantics.
  260. I made that argument,
  261. --oh, my god!
    I don't want to think about it!--
  262. more that 30 years ago,
  263. but there is a deeper argument
    implicit in what I've told you.
  264. And I want to tell you that argument
    briefly, and that is:
  265. consciousness creates an observer
    independent reality.
  266. It creates a reality of money,
    property, government,
  267. marriage, CERN, conferences,
  268. cocktail parties, and summer vacations.
  269. And all of those
    are creations of consciousness.
  270. Their existence is observer-relative.
  271. It's only relative to conscious agents;
  272. that a piece of paper is a money,
  273. or a bunch of buildings is a university.
  274. Now, ask yourselves about computation.
  275. Is that absolute?
  276. Like force, and mass,
    and gravitational attraction?
  277. Or is it observer-relative?
  278. Well, some computations are intrinsic.
  279. I add two plus two to get four,
  280. that's going on no matter
    what anybody thinks.
  281. But when I hold out my pocket calculator
    and do the calculation,
  282. the only intrinsic phenomenon
  283. is the electronic circuit
    and its behavior.
  284. That's the only absolute phenomenon.
  285. All the rest is interpreted by us.
  286. Computation only exists
    relative to consciousness.
  287. Either a conscious agent
    is carrying the computation
  288. or it has a piece of machinery
  289. that admits
    of a computational interpretation.
  290. That doesn't mean
    computation is arbitrary,
  291. I spent a lot of money
    on this hardware,
  292. but we have this persistent confusion
  293. between objectivity and subjectivity
  294. as features of reality,
  295. and objectivity and subjectivity
  296. as features of claims.
  297. And the bottom line
    of this part of my talk, is this:
  298. you can have
    a completely objective science,
  299. a science where you make
    objectively true claims
  300. about a domain whose existence
    is subjective,
  301. whose existence is in the human brain,
  302. consisting of subjective states
    or sensations, or feeling, or awareness.
  303. So the objection, that you can't have
    an objective science of consciousness
  304. because it's subjective,
    and science is objective,
  305. that's a pun, that's a bad pun
    on objectivity and subjectivity.
  306. You can make objective claims
    about a domain that is subjective
  307. in its mode of existence,
  308. and indeed, that's what neurologists do.
  309. You have patients
    that actually suffered pains
  310. and you are trying to get
    an objective science of that.
  311. I promised to refute all these guys,
  312. but I don't have
    an awful lot of time left,
  313. but let me refute a couple more of them.
  314. I said that behaviorism ought to be
    one of the great embarrassments
  315. of our intellectual culture,
  316. because it's refuted the moment
    you think about it.
  317. Your mental states are identical
    with your behavior?
  318. Well, think about the distinction
    between feeling a pain,
  319. and engaging in pain behavior.
  320. I mean, I won't demonstrate pain behavior
  321. but I can tell you
    I am not having any pains right now!
  322. So it's an obvious mistake.
  323. Why did they make the mistake?
  324. The mistake was, and you go back
  325. and ready the literature on this,
    you can see this over and over,
  326. they think [that] if you accept
  327. the irreducible existence
    of consciousness,
  328. you're giving up on science,
  329. you're giving up on 300 years
  330. of human progress and human hope
    and all the rest of it.
  331. And the message
    I want to leave you with is
  332. consciousness has to become accepted
    as a genuine biological phenomenon,
  333. as much subject to scientific analysis
  334. as any other phenomena in biology,
    or, for that matter,
  335. the rest of science!
  336. Thank you very much.
  337. (Applause)