on dretske's the epistemology of belief

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.