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'.

1. The Epistemology of Belief
By Fred Dretske
presented with commentary by
Sebastian Benthall

2. Epistemology and skepticism

3. epistemology, n.
Etymology: < Greek EPISTEMO- knowledge +
-LOGIA discoursing >
The theory or science of the method or grounds of
knowledge.

4. skepticism, n.
Etymology: < Neo-Latin scepticismus, equivalent to
Latin sceptic ( us ) skeptic + -ismus -ism
The doctrine that true knowledge or knowledge in a
particular area is uncertain.

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 judge's 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. Everyone's 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 on
modern Western philosophical skepticism

7. How do we know anything at all?
René Descartes
(1596 - 1650) An evil demon

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. How do we know anything at all?
Hilary Putnam Evil Scientist
(1926 - )

10. How do we know anything at all?
Hilary Putnam Brain in a Vat
(1926 - )

11. How do we know anything at all?
Wachowski brothers, 1999

12. How do we know anything at all?
Beliefs Information World

13. How do we know anything at all?
Beliefs Information World

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. 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. Fred Dretske
(1932 - )

17. “The Epistemology of Belief”
Fred Dretske, 1983

18. [Any questions so far?]

19. Dretske on
Representation and Misrepresentation

20. You can't fool an instrument

21. You can't 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. You can't fool a frog
Beliefs Information World

23. You can't fool a frog

24. You can't fool a frog
?

25. You can't fool a frog

26. You can't fool a frog

27. You can't fool a frog

28. You can't fool a frog

29. You can't fool a frog

30. You can't fool a frog

31. You can't 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. You can't 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. [Any questions?]

34. Dretske on Learning

35. You can't fool a dolphin
Beliefs Information World

36. You can't fool a dolphin
Beliefs Information World

37. You can't fool a dolphin
Beliefs Information World

38. You can't fool a dolphin

39. You can't fool a dolphin
?

40. You can't fool a dolphin

41. You can't fool a dolphin

42. You can't fool a dolphin

43. You can't fool a dolphin

44. You can't fool a dolphin

45. “... the decision about what sorts of beliefs we
may attribute to [a creature] is guided by our
assessment of the sort of information the animal
utilizes during learning...”

46. [Any questions?]

47. Dretske Defines Information

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. What is information?
“I mean nothing very technical or abstract.”

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. 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 a
dingbat 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. 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. Question:
Is that how you use the term
“information [about]”?

54. Question:
Is there an example of M “information about” Y
such that
one could not learn Y from M?

55. Question:
Is there an example of
M from which one could learn Y
such that
M is not “information about” Y?

56. Dretske versus the Skeptic

57. Take that, skeptic!

If a person can believe that X is Y, then they
must be capable of processing information
about Y

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. 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. Take that, skeptic!
I believe that's a tree.
Therefore, I can
know that's a tree.
Take that, skeptic!

61. Ta da!

62. Question:
Has Dretske defeated
the skeptic?

63. Take that, Twin Earth!
Earth Twin Earth

64. Dretske Qualifies his Argument

65. His argument applies only to
'simple concepts'
(We build complex concepts from
simple ones)
E.g. unicorns and randomness

66. The last line:
“If the information we receive about X's 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 X's.
But we also have a problem about how we can
ever believe that there are X's.”

67. How do we believe anything at all?
Beliefs Information World

68. How do we believe anything at all?
Beliefs Information World

69. How do we believe anything at all?
Beliefs Information World

70. How do we believe anything at all?
Beliefs Information World

71. How do we believe anything at all?
Beliefs Information World

72. How do we believe anything at all?
Beliefs Information World

73. How do we believe anything at all?

74. Questions or comments?

75. What does this tell
us about information?
[we're leaving the territory of the paper now]

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. 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. 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. 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. 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. What is information?
M has whatever reliable connection with Y is
required to enable
a suitably equipped, but otherwise ignorant
receiver,
to learn from M that X is a Y.

82. What is information?
M carries information that X is Y iff M has
whatever reliable connection is
required to enable to learn
a suitably equipped receiver
that is otherwise ignorant
that X is a Y

83. What is information?
M carries information that X is Y iff M has
whatever reliable connection is
required to enable to learn Can you learn
something if you
aren't ignorant of it at
a suitably equipped receiver first?
that is otherwise ignorant ← Redundant!
Simplify!
that X is a Y

84. What is information?
M carries information that X is Y iff M has
whatever reliable connection is This is just telling us
that we shouldn't
expect rocks to learn
required to enable to learn from information.
If something is not
'suitably equipped' it
a suitably equipped receiver cannot be 'enabled to
learn'.
that X is a Y

85. What is information?
M carries information that X is Y iff M has
whatever reliable connection is This is just telling us
that we shouldn't
expect rocks to learn
required to enable to learn from information.
If something is not
'suitably equipped' it
a 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. What is information?
M carries information that X is Y iff M has
whatever reliable connection is
required to enable [one] to learn
that X is a Y

87. You can't fool a dolphin

88. Whatever reliable connection
Beliefs Information World
This sonar image of X is
information that
X is a cylinder, not X is plastic

89. Whatever reliable connection
Beliefs Information World
This sonar image of X is
“reliably connected” to
X's being a cylinder, not X's being plastic

90. Whatever reliable connection
Beliefs Information World
Proposal:
The
reliable connection required to enable one to learn
from M that X is Y is
M(X)'s statistical correlation with Y(X)

91. Whatever reliable connection

92. Shannon defined
mutual information
as a measure of information about
variable A in another variable B

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. 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. Shannon defined
mutual information

96. Whatever reliable connection

97. Whatever reliable connection

98. Whatever reliable connection
Sonar Shape,
Material
I(Sonar : Shape) = 1
I(Sonar : Material) = 0

99. What is information?
M carries information that X is Y iff M has
whatever reliable connection is
required to enable [one] to learn
that X is a Y

100. What is information?
M carries information that X is Y iff
M and Y have
mutual information (in Shannon's sense)
when considered over all X's

101. Questions/Comments/Discussion
And, thanks for listening.