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On Dretske's The Epistemology of Belief

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This presentation introduces the philosophical field of epistemology and the problem of skepticism. It then outlines Fred Dretske's response to the problem. Lastly, it argues that Dretske's use of information reduces to Shannon's 'mutual information'.

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On Dretske's The Epistemology of Belief

  1. 1. The Epistemology of Belief By Fred Dretske presented with commentary by Sebastian Benthall
  2. 2. Epistemology and skepticism
  3. 3. epistemology, n.Etymology: < Greek EPISTEMO- knowledge +-LOGIA discoursing >The theory or science of the method or grounds ofknowledge.
  4. 4. skepticism, n.Etymology: < Neo-Latin scepticismus, equivalent toLatin sceptic ( us ) skeptic + -ismus -ismThe doctrine that true knowledge or knowledge in aparticular area is uncertain.
  5. 5. How do we know anything at all? “Those who claim for themselves to judge the truth are bound to possess a criterion of truth. This criterion, then, either is without a judges approval or has been approved. But if it is without approval, whence comes it that it is truthworthy? For no matter of dispute is to be trusted without judging. And, if it has been approved,Sextus Empiricus that which approves it, in turn,(160 – 210 AD) either has been approved or has not been approved, and so on ad infinitum.”
  6. 6. Everyones a skeptic Skepticism is very old and broad There are skeptical traditions in Ancient Greece, Buddhism, Hinduism, Daoism, Islam (just check Wikipedia!) We will focus onmodern Western philosophical skepticism
  7. 7. How do we know anything at all? René Descartes (1596 - 1650) An evil demon
  8. 8. How do we know anything at all? “It is at least possible that there is an all- powerful evil demon who is deceiving me, such that he causes me to have false beliefs.” - Meditations of First René Descartes Philosophy, 1641 (1596 - 1650)
  9. 9. How do we know anything at all? Hilary Putnam Evil Scientist (1926 - )
  10. 10. How do we know anything at all? Hilary Putnam Brain in a Vat (1926 - )
  11. 11. How do we know anything at all? Wachowski brothers, 1999
  12. 12. How do we know anything at all? Beliefs Information World
  13. 13. How do we know anything at all? Beliefs Information World
  14. 14. How do we know anything at all? This is called global skepticism If the global skeptic wins, epistemology loses If epistemology loses, we all lose  How can we justify our beliefs?  Without standards of justification, we are at the mercy of charlatans, propagandists, and demagogues  Science, law, history, religion...
  15. 15. How do we know anything at all? If we can beat the global skeptic, we sharpen our idea of how we know and can learn more There are many contenders:  empiricism, rationalism, constructivism, foundationalism, coherentism, pragmatism ...  Basically every major philosopher since Descartes and several before him have tackled this issue
  16. 16. Fred Dretske (1932 - )
  17. 17. “The Epistemology of Belief” Fred Dretske, 1983
  18. 18. [Any questions so far?]
  19. 19. Dretske onRepresentation and Misrepresentation
  20. 20. You cant fool an instrument
  21. 21. You cant fool an instrument Consider the speedometer. What does it represent? If you lift the car off the road, does it misrepresent the speed of the car? Does it believe something wrong? Is it saying something incorrect? Dretske: It is time to stop describing instruments in such inappropriate ways.
  22. 22. You cant fool a frogBeliefs Information World
  23. 23. You cant fool a frog
  24. 24. You cant fool a frog?
  25. 25. You cant fool a frog
  26. 26. You cant fool a frog
  27. 27. You cant fool a frog
  28. 28. You cant fool a frog
  29. 29. You cant fool a frog
  30. 30. You cant fool a frog
  31. 31. You cant fool a frog “The frog gets hungry in this situation, not because it mistakenly sees dark spots as edible bugs, but because what it correctly sees as moving spots are not, in fact, edible bugs.”
  32. 32. You cant fool a frog “The frog gets hungry in this situation, not because it mistakenly sees dark spots as edible bugs, but because what it correctly sees as moving spots are not, in fact, edible bugs.”
  33. 33. [Any questions?]
  34. 34. Dretske on Learning
  35. 35. You cant fool a dolphinBeliefs Information World
  36. 36. You cant fool a dolphinBeliefs Information World
  37. 37. You cant fool a dolphinBeliefs Information World
  38. 38. You cant fool a dolphin
  39. 39. You cant fool a dolphin ?
  40. 40. You cant fool a dolphin
  41. 41. You cant fool a dolphin
  42. 42. You cant fool a dolphin
  43. 43. You cant fool a dolphin
  44. 44. You cant fool a dolphin
  45. 45. “... the decision about what sorts of beliefs we may attribute to [a creature] is guided by ourassessment of the sort of information the animal utilizes during learning...”
  46. 46. [Any questions?]
  47. 47. Dretske Defines Information
  48. 48. What is information?“I have begun to talk more and more about information so let me pause a moment to explain what I mean by this way of talking.”
  49. 49. What is information?“I mean nothing very technical or abstract.”
  50. 50. What is information?“In fact, I mean pretty much what (I think) we all mean in talking of some event, signal, or structure carrying (or embodying) information about another state of affairs.”
  51. 51. What is information?“[A] message carries the information that X is a dingbat, say, if and only if one could learn (come to know) that X was a dingbat from the message.”“When I say that one could learn that X was adingbat from the message, I mean, simply, that the message has whatever reliable connection with dingbats is required to enable a suitably equipped, but otherwise ignorant receiver, to learn from it that X is a dingbat.”
  52. 52. What is information?def information := a message M carries the information that X is Y if and only if one could learn that X is Y from M.def one could learn := one could learn that X was Y from M if and only if M has whatever reliable connection with Y is required to enable a suitably equipped, but otherwise ignorant receiver, to learn from it that X is a Y.
  53. 53. Question:Is that how you use the term “information [about]”?
  54. 54. Question:Is there an example of M “information about” Y such that one could not learn Y from M?
  55. 55. Question: Is there an example ofM from which one could learn Y such thatM is not “information about” Y?
  56. 56. Dretske versus the Skeptic
  57. 57. Take that, skeptic! If a person can believe that X is Y, then they must be capable of processing information about Y
  58. 58. Take that, skeptic! If a person can believe that X is Y, then they must be capable of processing information about Y If one is capable of processing information about Y, then one must be capable of knowing Y (from the information)
  59. 59. Take that, skeptic! If a person can believe that X is Y, then they must be capable of processing information about Y If one is capable of processing information about Y, then one must be capable of knowing Y (from the information) Therefore, if a person can believe that X is Y, they must be capable of knowing that things can be Y (from information)
  60. 60. Take that, skeptic! I believe thats a tree. Therefore, I can know thats a tree. Take that, skeptic!
  61. 61. Ta da!
  62. 62. Question:Has Dretske defeated the skeptic?
  63. 63. Take that, Twin Earth!Earth Twin Earth
  64. 64. Dretske Qualifies his Argument
  65. 65. His argument applies only to simple concepts(We build complex concepts from simple ones) E.g. unicorns and randomness
  66. 66. The last line:“If the information we receive about Xs is always too impoverished to specify an X as an X, then, admittedly,we have an epistemological problem about how we can ever know that there are Xs. But we also have a problem about how we can ever believe that there are Xs.”
  67. 67. How do we believe anything at all? Beliefs Information World
  68. 68. How do we believe anything at all? Beliefs Information World
  69. 69. How do we believe anything at all? Beliefs Information World
  70. 70. How do we believe anything at all? Beliefs Information World
  71. 71. How do we believe anything at all? Beliefs Information World
  72. 72. How do we believe anything at all? Beliefs Information World
  73. 73. How do we believe anything at all?
  74. 74. Questions or comments?
  75. 75. What does this tell us about information?[were leaving the territory of the paper now]
  76. 76. What is information?def information := a message M carries the information that X is Y if and only if one could learn that X is Y from M.def one could learn := one could learn that X was Y from M if and only if M has whatever reliable connection with Y is required to enable a suitably equipped, but otherwise ignorant receiver, to learn from it that X is a Y.
  77. 77. What is information?def information := a message M carries the information that X is Y if and only if one could learn that X is Y from M.def one could learn := one could learn that X was Y from M if and only if M has whatever reliable connection with Y is required to enable a suitably equipped, but otherwise ignorant receiver, to learn from it that X is a Y.
  78. 78. What is information?def information := a message M carries the information that X is Y if and only if M has whatever reliable connection with Y is required to enable a suitably equipped, but otherwise ignorant receiver, to learn from it that X is a Y.
  79. 79. What is information?def information := a message M carries the information that X is Y if and only if M has whatever reliable connection with Y is required to enable a suitably equipped, but otherwise ignorant receiver, to learn from it that X is a Y.
  80. 80. What is information?def information := a message M carries the information that X is Y if and only if M has whatever reliable connection with Y is required to enable a suitably equipped, but otherwise ignorant receiver, to learn from it that X is a Y. What is this?
  81. 81. What is information?M has whatever reliable connection with Y is required to enablea suitably equipped, but otherwise ignorant receiver,to learn from M that X is a Y.
  82. 82. What is information?M carries information that X is Y iff M haswhatever reliable connection isrequired to enable to learna suitably equipped receiverthat is otherwise ignorantthat X is a Y
  83. 83. What is information?M carries information that X is Y iff M haswhatever reliable connection isrequired to enable to learn Can you learn something if you arent ignorant of it ata suitably equipped receiver first?that is otherwise ignorant ← Redundant! Simplify!that X is a Y
  84. 84. What is information?M carries information that X is Y iff M haswhatever reliable connection is This is just telling us that we shouldnt expect rocks to learnrequired to enable to learn from information. If something is not suitably equipped ita suitably equipped receiver cannot be enabled to learn.that X is a Y
  85. 85. What is information?M carries information that X is Y iff M haswhatever reliable connection is This is just telling us that we shouldnt expect rocks to learnrequired to enable to learn from information. If something is not suitably equipped ita suitably equipped receiver cannot be enabled to learn.that X is a Y But “required to” implies a necessary, not sufficient, condition. So we can simplify.
  86. 86. What is information?M carries information that X is Y iff M haswhatever reliable connection isrequired to enable [one] to learnthat X is a Y
  87. 87. You cant fool a dolphin
  88. 88. Whatever reliable connection Beliefs Information World This sonar image of X is information that X is a cylinder, not X is plastic
  89. 89. Whatever reliable connection Beliefs Information World This sonar image of X is “reliably connected” toXs being a cylinder, not Xs being plastic
  90. 90. Whatever reliable connection Beliefs Information World Proposal: Thereliable connection required to enable one to learn from M that X is Y is M(X)s statistical correlation with Y(X)
  91. 91. Whatever reliable connection
  92. 92. Shannon defined mutual informationas a measure of information about variable A in another variable B
  93. 93. Shannon defined mutual information I(A : B) = H(B) – H(B|A)Recall H is entropy of a distribution. H(B|A) is conditional entropy.
  94. 94. Shannon defined mutual information I(A : B) = H(B) – H(B|A)I(A:B) is a measure of the correlation between A and B.
  95. 95. Shannon definedmutual information
  96. 96. Whatever reliable connection
  97. 97. Whatever reliable connection
  98. 98. Whatever reliable connection Sonar Shape, Material I(Sonar : Shape) = 1 I(Sonar : Material) = 0
  99. 99. What is information?M carries information that X is Y iff M haswhatever reliable connection isrequired to enable [one] to learnthat X is a Y
  100. 100. What is information?M carries information that X is Y iffM and Y havemutual information (in Shannons sense)when considered over all Xs
  101. 101. Questions/Comments/Discussion And, thanks for listening.

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