Descartes and Russell - PowerPoint Presentation

Slide1

Descartes and Russell

James C. BlackmonSlide2

Descartes on the External WorldSlide3

Skepticism and Foundationalism

An “Argument” for Skepticism

To know that P requires that P is justified by some reason R.

But for R to justify P, R must be known.

This chain of justification cannot go on forever, can’t go in a circle, and cannot stop at some point.

Thus, nothing can be known. Slide4

Skepticism and Foundationalism

Descartes rejects epistemological skepticism, but he recognizes its potency:

It would seem that anything can be doubted.

If so, then one can require a reason for believing anything.

Descartes doesn’t seem to believe that infinite chains or closed loops of justification can help, so he hopes to find that the chain of justification

does stop at some point. Thus, Descartes adopts methodological skepticism

.Slide5

Skepticism and Foundationalism

Methodological Skepticism: The view that all propositions should be open to intense scrutiny and that we should subject them to intense scrutiny for the sake of discerning their truth or falsity. (This does not have to be done one belief at a time; we can intensely scrutinize general claims.)

Cartesian Method: Adopt methodological skepticism in the hope that something will prove to be indubitable (impossible to doubt). If so, then whatever that proposition or belief is, it needs no further justification.Slide6

Skepticism and Foundationalism

An Analogy

In questioning everything, it’s as if Descartes wants to dig until he hits bedrock—until he reaches a point where he cannot dig any further.Slide7

Skepticism and Foundationalism

An Analogy

Descartes holds that any individual can, through this kind of “meditation”, discover the bedrock—the foundation—on which the rest of our knowledge might be rebuilt.Slide8

Skepticism and Foundationalism

An Analogy

Descartes holds that any individual can, through this kind of “meditation”, discover the bedrock—the foundation—on which the rest of our knowledge might be rebuilt.

But first, let’s see just how skeptical we can be

.Slide9

Skepticism and Foundationalism

Two Arguments

The Dream Argument

The Evil Genius Argument

Both are products of his methodological skepticism.Slide10

Skepticism and Foundationalism

The Dream Argument

I don’t know that P unless I know that I’m not dreaming.

I don’t know that I’m not dreaming.

Thus I don’t know that P.Slide11

Skepticism and Foundationalism

The Evil Genius Argument

I don’t know that P unless I know that I’m not being deceived by an evil genius.

I don’t know that I’m not being

deceived by an evil genius

.Thus I don’t know that P.Slide12

Skepticism and Foundationalism

The Evil Genius Argument

I don’t know that P unless I know that I’m not being deceived by an evil genius.

I don’t know that I’m not being

deceived by an evil genius

.Thus I don’t know that P.

The Evil Genius could deceive me about almost everything: even my own body might be different or nonexistent.Slide13

Skepticism and Foundationalism

The Cogito: I think. (I am. Or I, as a thinking thing, exist.)Slide14

Skepticism and Foundationalism

The Cogito: I think. (I am. Or I, as a thinking thing, exist.)

Two Principles of Deception

If I am deceived that P, then P is false.

If I am deceived about P, then I exist.Slide15

Skepticism and Foundationalism

Two Principles of Deception

If I am deceived that P, then P is false.

If I am deceived about P, then I exist.

Let P =

I exist. Then, by 1, it is false that I exist.But by 2, it is true that I exist.So, I both don’t exist and do exist? Impossible!Slide16

Skepticism and Foundationalism

Two Principles of Deception

If I am deceived that P, then P is false.

If I am deceived about P, then I exist.

Let P =

I exist. Then, by 1, it is false that I exist.But by 2, it is true that I exist.So, I both don’t exist and do exist? Impossible!Slide17

Skepticism and Foundationalism

So, no matter however else I am deceived, I find it to be certain that I, insofar as I am a thinking thing, exist.

Cogito = I thinkSlide18

Skepticism and Foundationalism

So, no matter however else I am deceived, I find it to be certain that I, insofar as I am a thinking thing, exist.

Cogito = I think

Existence is the precondition of thought, doubt, error, and all other mental states.Slide19

Skepticism and Foundationalism

But what am I?

I cannot yet say I’m a man.

Or a rational animal.

I cannot even say I’m a body or thing which has a body.

I am essentially a think which thinks, a soul or mind.Slide20

Skepticism and Foundationalism

But what am I?

I cannot yet say I’m a man.

Or a rational animal.

I cannot even say I’m a body or thing which has a body.

I am essentially a think which thinks, a soul or mind.Slide21

Skepticism and Foundationalism

Why does Descartes spend so much time talking about the wax?Slide22

Skepticism and Foundationalism

Why does Descartes spend so much time talking about the wax?

He’s trying to determine whether the existence of the “I” is more or less understood than physical objects we see and feel.Slide23

Skepticism and Foundationalism

The Wax

The wax has sweetness, odor, shape, color, …

All kinds of sensible forms.Slide24

Skepticism and Foundationalism

The Wax

The wax has sweetness, odor, shape, color, …

All kinds of sensible forms.

Now, placed near the fire, the wax loses all of these forms.Slide25

Skepticism and Foundationalism

The Wax

The wax has sweetness, odor, shape, color, …

All kinds of sensible forms.

Now, placed near the fire, the wax loses all of these forms.

And yet the wax remains.Slide26

Skepticism and Foundationalism

If the forms are gone and the wax remains, then the wax is not merely composed of its forms.Slide27

Skepticism and Foundationalism

If the forms are gone and the wax remains, then the wax is not merely composed of its forms.

Moreover, if I knew the wax by its forms, then I wouldn’t know the wax has survived being heated and losing them.Slide28

Skepticism and Foundationalism

If the forms are gone and the wax remains, then the wax is not merely composed of its forms.

Moreover, if I knew the wax by its forms, then I wouldn’t know the wax has survived being heated and losing them.

So how do I know the wax?Slide29

Skepticism and Foundationalism

Descartes wants to determine what has priority:

The senses,

The imagination, or

Our faculty of judgment?Slide30

Skepticism and Foundationalism

We do not know the wax through the senses.

The senses know the forms, but those forms are gone, replaced by others.

We sense nothing which has survived this change.

And yet we still have wax.Slide31

Skepticism and Foundationalism

We do not know the wax through the imagination.

For, we cannot exhaust all possibilities of imagined wax.

For instance, there are infinitely many shapes it could take.Slide32

Skepticism and Foundationalism

We must know the wax through the mind, the faculty of judgment.Slide33

Skepticism and Foundationalism

We must know the wax through the mind, the faculty of judgment.

I see the forms.

I

judge

that there is wax.Slide34

Skepticism and Foundationalism

We must know the wax through the mind, the faculty of judgment.

I see the forms.

I

judge

that there is wax.Similarly,I see the hats and coats of the pedestrians out my window.I judge that people wear them.Slide35

Skepticism and Foundationalism

Sensing of these forms strongly suggests the existence of a physical thing, wax, which has them.

But judging that the wax exists

entails

that I—a sensing, perceiving, judging thing—exist.Slide36

Skepticism and Foundationalism

Consequently

When I judge that there is wax, based on the forms I sense, I’m strongly inclined to say I perceive the wax.

However, I must admit that I might only perceive these forms, just as I might only perceive hats and coats, not people. In other words, I could be wrong.Slide37

Skepticism and Foundationalism

Consequently

When I judge that there is wax, based on the forms I sense, I’m strongly inclined to say I perceive the wax.

However, I must admit that I might only perceive these forms, just as I might only perceive hats and coats, not people. In other words, I could be wrong.

So, although the wax seemed more distinct than the self, I now realize that it is not.Slide38

Skepticism and Foundationalism

Consequently

When I judge that there is wax, based on the forms I sense, I’m strongly inclined to say I perceive the wax.

However, I must admit that I might only perceive these forms, just as I might only perceive hats and coats, not people. In other words, I could be wrong.

So, although the wax seemed more distinct than the self, I now realize that it is not.

For, again, judging that wax exists requires (and thus entails) that I exist, but it does not require that wax exists.Slide39

Skepticism and Foundationalism

How Descartes Proceeds from Here

Now that Descartes has found a firm foundation (like the Archimedean point), he must rebuild his knowledge. Otherwise, he’s stuck with solipsism: skepticism about everything but one’s own mind and its contents.

In order to rebuild knowledge of the external world, Descartes needs to know that his senses don’t generally deceive him.

For this, he uses God.Slide40

Skepticism and Foundationalism

How Descartes Proceeds from Here

God would not allow him to be deceived in principle; thus, Descartes can trust his senses in general, even if hasty use of them can be misleading. Slide41

Skepticism and Foundationalism

How Descartes Proceeds from Here

If God (omnipotent and perfectly good) exists, then my senses do not deceive me in principle and my inclination to believe in external objects is not misleading.

God exists.

My

senses do not deceive me in principle and my inclination to believe in external objects is not misleading.Slide42

Skepticism and Foundationalism

How Descartes Proceeds from Here

For Descartes, God’s existence and nature provide the bridge from certainty of our sensory experience to certainty of the existence of an external world.Slide43

Skepticism and Foundationalism

How Descartes Proceeds from Here

For Descartes, God’s existence and nature provide the bridge from certainty of our sensory experience to certainty of the existence of an external world.

This does

not

mean we can’t hallucinate or be fooled by other experiences.But it does mean we do not have to worry anymore that an external world of some kind of other doesn’t exist.Slide44

Readings

Descartes:

Meditations

I

and IIRussell: Chapters 1, 2, 3Berkeley: Selections from Of the Principles of Human Knowledge Russell: Chapter 4Quine: Posits and Reality

[5 pages]

Putnam:

Brains in a Vat

[7 pages]

Chalmers:

The Matrix as Metaphysics

[13 pages]Slide45

Russell on the External WorldSlide46

Russell

Russell objects to Descartes’ argument.

Russell finds that we are

more

certain of the existence of table (wax) experiences than of our own selves.

“When I look at my table and see a certain brown colour, what is quite certain at once is not ‘I am seeing a brown colour’, but rather, ‘a brown color is being seen’. [19]

Whatever x which sees it might be momentary.

Russell seems to consider such momentary things to be unsuitable candidates for

I

.Slide47

Russell

The Problem

“Granted that we are certain of our own sense-data, have we any reason for regarding them as signs of the existence of something else, which we can call the physical object?” [19-20]

In other words, can we adopt Model 1?Slide48

Russell

The Problem

“Granted that we are certain of our own sense-data, have we any reason for regarding them as signs of the existence of something else, which we can call the physical object?” [19-20]

In other words, can we adopt Model 1?

Common sense: Yes.

We buy and sell the table, not just the sense-data it causes.We make its sense-data disappear by covering it with a table cloth, but we don’t make the table disappear. Skepticism is absurd.Slide49

Russell

The Problem

“Granted that we are certain of our own sense-data, have we any reason for regarding them as signs of the existence of something else, which we can call the physical object?” [19-20]

We want the

same

object for different people: Public Neutral Objects (PNOs).Public: Everyone can access the physical object, even if it gives each person a different set of sense-data.Neutral: The physical object equally determines each person’s sense-data (based on the person’s sensory faculties and environment).Slide50

Russell

Russell first considers a bad argument in favor of PNOs.

A Fallacious Argument for PNOs

Different people have similar sense data.

If different people have similar sense data, then this can be explained by the existence of PNOs.

Thus, we have good reason to believe in PNOs.Slide51

Russell

Russell

first considers

a bad argument in favor of PNOs

.

A Fallacious Argument for PNOsDifferent people have similar sense data.If different people have similar sense data, then this can be explained by the existence of PNOs.

Thus, we have good reason to believe in PNOs.Slide52

Russell

Russell

first considers

a bad argument in favor of PNOs

.

Different people have similar sense data.We aren’t allowed to assume that there are different people out there! We must remain solipsists.If we are trying to show that there are objects independent of our own sense-data, we cannot appeal to the testimony of others; for, this testimony itself is subject to the same skepticism as the table.Slide53

Russell

Russell

first considers

a bad argument in favor of PNOs

.

Different people have similar sense data.We aren’t allowed to assume that there are different people out there! We must remain solipsists.If we are trying to show that there are objects independent of our own sense-data, we cannot appeal to the testimony of others; for, this testimony itself is subject to the same skepticism as the table.Slide54

Russell

Russell then appeals to simplicity in order to argue favor of PNOs.

A Simplicity Argument for PNOs: Russell’s Cat

The coherence of my sense-data of, for example, the cat at different times is

more simply explained

by a publically neutral cat than by nothing but sense-data.If x is more simply explained by hypothesis H, then I have good reason to believe H.

I have good reason to believe in a publically neutral cat.Slide55

Russell

Russell then appeals to simplicity in order to argue favor of PNOs.

In other words, the common-sense hypothesis (Model 1), provides the simplest explanation of what we know for certain: that I have a stream of relatively coherent sense-data. Slide56

Russell

Russell then appeals to simplicity in order to argue favor of PNOs.

In other words, the common-sense hypothesis (Model 1), provides the simplest explanation of what we know for certain: that I have a stream of relatively coherent sense-data.

Russell’s argument is an argument from the simplest explanation.Slide57

Russell

Russell then appeals to simplicity in order to argue favor of PNOs.

Where Descartes took himself to have established that he could be certain he was not deceived about the external world, Russell concedes that it is logically possible there are no PNOs.

However, he thinks we have not the slightest reason to adopt this external world skepticism.Slide58

Russell

What can we know about physical objects?

Public and neutral

Mind-independentSlide59

Russell

What can we know about physical objects?

Public and neutral

Mind-independent

Russell’s conclusion: Not much.Slide60

Russell

What can we know about physical objects?

Some terminological quibbles [See

28]

Despite Russell’s claims (circa 1912), many philosophers

today would not call aether or an electromagnetic field or any other massless field

matter

.

Russell uses the term ‘light’ to pick out our sensation; others use it to pick out the mind-independent cause of it, which science tells us is a wave (or a collection of photons). Such ambiguities of ‘light’, ‘sound’, ‘color’ are common and persist through to this day.Slide61

Russell

What can we know about physical objects?

Some terminological quibbles [See

28]

If a tree fell in the woods…Slide62

Russell

What can we know about physical objects?

Russell distinguishes between apparent (also private) space and real space. Similarly, between apparent shape and real shape.

The circular coin can look oval.

It has the apparent shape of oval because it corresponds to an oval sense-data in ones apparent space, but it has the real shape of circular in real space.We take it that (under suitable conditions) latter causes the former.Slide63

Russell

What can we know about physical objects?

As with Locke, your sense-data of a PNO is a function of three things:

Your physical state

The PNO’s physical state, andEnvironmental conditions. [35]Slide64

Russell

What can we know about physical objects?

But

contra

Locke, we can know “only what is required in order to secure the correspondence” between the sense-data and the PNOs.How the PNOs are arranged wrt each other can be known from how their sense-data are arranged in our experience.But what the PNOs are in themselves is unknowable.Slide65

Russell

What can we know about physical objects?

But

contra

Locke, we can know “only what is required in order to secure the correspondence” between the sense-data and the PNOs.How the PNOs are arranged wrt each other can be known from how their sense-data are arranged in our experience.But what the PNOs are in themselves is unknowable.

The same goes for time between events.Slide66

Russell

What can we know about physical objects?

But

contra

Locke, we can know “only what is required in order to secure the correspondence” between the sense-data and the PNOs.How the PNOs are arranged wrt each other can be known from how their sense-data are arranged in our experience.But what the PNOs are in themselves is unknowable.

The same goes for time between events.

Our knowledge of the physical world is thus

relational

.Slide67

Russell

What can we know about physical objects?

“…although the

relations

of physical objects have all sorts of knowable properties, derived from their correspondence with the relations of sense-data, the physical objects themselves remain unknown in their intrinsic nature, so far at least as can be discovered by means of the senses.” [34]Slide68

Russell

What can we know about physical objects?

On 35, Russell appears to use parsimony or some version of Ockham’s Razor to reject the notion that physical objects have color.Slide69

Russell

What can we know about physical objects?

On 35, Russell appears to use parsimony or some version of Ockham’s Razor to reject the notion that physical objects have color.

How far can this kind of reasoning go?