on dretske's the epistemology of belief
DESCRIPTION
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'.TRANSCRIPT
The Epistemology of BeliefBy Fred Dretske
presented with commentary bySebastian Benthall
Epistemology and skepticism
epistemology, n.Etymology: < Greek EPISTEMO- knowledge + -LOGIA discoursing >
The theory or science of the method or grounds of knowledge.
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.
How do we know anything at all?
Sextus Empiricus(160 – 210 AD)
“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, that which approves it, in turn, either has been approved or has not been approved, and so on ad infinitum.”
Everyone's a skeptic
Skepticism is very old and broad
There are skeptical traditions inAncient Greece, Buddhism, Hinduism,
Daoism, Islam(just check Wikipedia!)
We will focus onmodern Western philosophical skepticism
How do we know anything at all?
René Descartes(1596 - 1650) An evil demon
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 Philosophy, 1641René Descartes
(1596 - 1650)
How do we know anything at all?
Hilary Putnam(1926 - )
Evil Scientist
How do we know anything at all?
Hilary Putnam(1926 - )
Brain in a Vat
How do we know anything at all?
Wachowski brothers, 1999
How do we know anything at all?
Beliefs Information World
How do we know anything at all?
Beliefs Information World
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...
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
Fred Dretske(1932 - )
“The Epistemology of Belief”Fred Dretske, 1983
[Any questions so far?]
Dretske onRepresentation and Misrepresentation
You can't fool an instrument
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.
You can't fool a frog
Beliefs Information World
You can't fool a frog
You can't fool a frog
?
You can't fool a frog
You can't fool a frog
You can't fool a frog
You can't fool a frog
You can't fool a frog
You can't fool a frog
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.”
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.”
[Any questions?]
Dretske on Learning
You can't fool a dolphin
Beliefs Information World
You can't fool a dolphin
Beliefs Information World
You can't fool a dolphin
Beliefs Information World
You can't fool a dolphin
You can't fool a dolphin
?
You can't fool a dolphin
You can't fool a dolphin
You can't fool a dolphin
You can't fool a dolphin
You can't fool a dolphin
“... 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...”
[Any questions?]
Dretske Defines 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.”
What is information?
“I mean nothing very technical or abstract.”
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.”
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.”
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.
What is information?
Question:
Is that how you use the term“information [about]”?
Question:
Is there an example of M “information about” Ysuch that
one could not learn Y from M?
Question:
Is there an example ofM from which one could learn Y
such thatM is not “information about” Y?
Dretske versus the Skeptic
Take that, skeptic!
If a person can believe that X is Y, then they must be capable of processing information about Y
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)
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)
Take that, skeptic!
I believe that's a tree.
Therefore, I can know that's a tree.
Take that, skeptic!
Ta da!
Question:
Has Dretske defeatedthe skeptic?
Take that, Twin Earth!
Earth Twin Earth
Dretske Qualifies his Argument
His argument applies only to'simple concepts'
(We build complex concepts fromsimple ones)
E.g. unicorns and randomness
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.”
How do we believe anything at all?
Beliefs Information World
How do we believe anything at all?
Beliefs Information World
How do we believe anything at all?
Beliefs Information World
How do we believe anything at all?
Beliefs Information World
How do we believe anything at all?
Beliefs Information World
How do we believe anything at all?
Beliefs Information World
How do we believe anything at all?
Questions or comments?
What does this tellus about information?
[we're leaving the territory of the paper now]
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.
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.
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 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 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?
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.
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
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
What is information?
Can you learn something if you aren't ignorant of it at first?
← Redundant! Simplify!
M carries information that X is Y iff M has
whatever reliable connection is
required to enable to learn
a suitably equipped receiver
that X is a Y
What is information?
This is just telling us that we shouldn't expect rocks to learn from information.
If something is not 'suitably equipped' it cannot be 'enabled to learn'.
M carries information that X is Y iff M has
whatever reliable connection is
required to enable to learn
a suitably equipped receiver
that X is a Y
What is information?
This is just telling us that we shouldn't expect rocks to learn from information.
If something is not 'suitably equipped' it cannot be 'enabled to learn'.
But “required to” implies a necessary, not sufficient, condition.
So we can simplify.
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
What is information?
You can't fool a dolphin
Whatever reliable connection
Beliefs Information World
This sonar image of X isinformation that
X is a cylinder, not X is plastic
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
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)
Whatever reliable connection
Shannon defined
mutual information
as a measure of information aboutvariable A in another variable B
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.
Shannon defined
mutual information
I(A : B) = H(B) – H(B|A)
I(A:B) is a measure of the correlationbetween A and B.
Shannon defined
mutual information
Whatever reliable connection
Whatever reliable connection
Whatever reliable connection
Sonar Shape, Material
I(Sonar : Shape) = 1
I(Sonar : Material) = 0
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
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
What is information?
Questions/Comments/Discussion
And, thanks for listening.