Epistemology:
Knowledge, Skepticism, and Ignorance
Clark Wolf
Director of Bioethics
Iowa State University
jwcwolf@iastate.edu
Argument for Analysis:
Everything I believe is consistent with the hypothesis that I am
being deceived by a powerful evil demon. But even a powerful
evil demon could not convince me that I don’t exist when in fact
I do exist. For when I doubt my existence, I immediately realize
that there must be something (or someone) doing the doubting.
When I doubt whether the statement “I exist” is true, I
immediately realize that it cannot be false, for the act of
doubting must be done by someone: by an “I” who must exist.
Even if I am deceived in everything else, I cannot be deceived–
cannot be wrong– about my own existence. “Thus, after
everything has been most carefully weighed, it must finally be
established that this pronouncement “I am, I exist” is
necessarily true every time I utter it or conceive it in my mind.”
(p. 493.1)
Everything I believe is consistent with the hypothesis that I am being deceived by a powerful
evil demon. But even a powerful evil demon could not convince me that I don’t exist when in
fact I do exist. For when I doubt my existence, I immediately realize that there must be
something (or someone) doing the doubting. When I doubt whether the statement “I exist” is
true, I immediately realize that it cannot be false, for the act of doubting must be done by
someone: by an “I” who must exist. Even if I am deceived in everything else, I cannot be
deceived– cannot be wrong– about my own existence. “Thus, after everything has been most
carefully weighed, it must finally be established that this pronouncement “I am, I exist” is
necessarily true every time I utter it or conceive it in my mind.” (p. 493.1)
1) When I try to doubt that the statement “I exist” is true, I realize that there must be some
subject (me) doing the doubting.
2) If there is a subject doing the doubting, that subject must exist.
3) Whenever I doubt the statement “I exist,” it is immediately evident that I exist.
4) Conclusion: The statement “I exist” is self evidently true.
Argument for Analysis:
I’m obviously imperfect, full of doubts and
false beliefs. But I have an idea of
perfection, and this idea is itself perfect.
Nothing imperfect could create something
perfect, so this perfect idea cannot have
come from me, it must have come to me
from another source. But only a perfect
source could cause a perfect idea. So there
must be a perfect being—God– who is the
cause of my perfect idea.
I’m obviously imperfect, full of doubts and false beliefs. But I have an idea of
perfection, and this idea is itself perfect. Nothing imperfect could create
something perfect, so this perfect idea cannot have come from me, it must
have come to me from another source. But only a perfect source could cause
a perfect idea. So there must be a perfect being—God– who is the cause of
my perfect idea.
1) I have a perfect idea.
2) Nothing perfect could come from something imperfect.
3) I am imperfect.
4) This perfect idea could not have come from me. (From 1,2,3)
5) Only a perfect being could be the cause of a perfect idea. (A new
claim, but interestingly related to premise 4.)
6) There must be a perfect being. (From 1,5)
7) If there is a perfect being, that being would be God.
8) Conclusion: God Exists. (From 6,7)
Argument for Analysis

Mind and body are either the same substance,
or they are different substances. If two things
are identical, then they will have all the same
properties. So if my mind and body are the
same substance, they must have all properties
in common. But I can doubt my body’s
existence– my body is dubitable. I can’t doubt
my mind’s existence– my mind is indubitable.
Therefore mind and body are different
substances.
Mind and body are either the same substance, or they are
different substances. If two things are identical, then they will
have all the same properties. So if my mind and body are the
same substance, they must have all properties in common. But
I can doubt my body’s existence– my body is dubitable. I can’t
doubt my mind’s existence– my mind is indubitable. Therefore
mind and body are different substances.
1) Mind and body are either the same thing, or they are
different substances.
2) If two things are identical, then they will have all the same
properties.
3) So if my mind and body are the same substance, they’ll have
all properties in common.
4) But I can doubt my body’s existence– my body is dubitable.
5) I can’t doubt my mind’s existence– my mind is indubitable.
6) Mind and body do not have all properties in common.
7) Therefore mind and body are different substances.
Argument for Analysis:
According to Descartes, we can’t know something
unless we are so absolutely certain that it is true that
we can’t doubt it. But if we accepted this, we would
be forced to conclude that we know nothing at all, or
almost nothing. It’s just wrong to say that we don’t
know something just because we can doubt that it’s
true, or just because it’s possible that it’s false: this
isn’t what we mean by the term ‘know.’ For example,
when I say “I know where I parked my bike, because I
remember doing it.” I don’t mean to indicate that I can’t
possibly be wrong about where I parked my bike, even
if it turns out that I’m a brain in a vat. So to know
something isn’t to be certain about it. So the
Cartesian analysis of knowledge doesn’t capture what
we typically mean by ‘knowledge.’
Argument for Analysis:
1) According to Descartes, we can’t know something
unless we are so absolutely certain that it is true that
we can’t doubt it.
2) But if we accepted this, we would be forced to
conclude that we know nothing at all, or almost
nothing.
3) But we know more than the Cartesian view would
support.
4) So to know something isn’t to be certain about it.
5) Descartes was wrong to believe that certainty is
necessary for knowledge.
SKEPTICISM:
Sextus Empiricus

Plato distinguished “knowledge” from
“opinion,” urging that we know only things
we discover through reason.

Aristotle and others call into question
Plato’s claim that we know the things Plato
thinks we know “through reason.”

So what do we know?
SKEPTICISM:
Sextus Empiricus

Question: What is knowledge?

CLAIM: You don’t know something unless
you have good evidence that it is true.

Question: Do you know that you are in a
philosophy classroom in Ames Iowa on a
cold March morning?
SKEPTICISM:
Sextus Empiricus
Thought Experiment:

(1) Do you know that the world did not
spring into existence four seconds ago.

(2) Do you know that you are not a brain in
a vat?
An Argument for Skepticism:








1) You have no evidence that you’re not a “brain in a
vat.”
2) If you have no evidence for X, then you don’t know X.
3) Therefore, You don’t know you’re not a brain in a vat.
4) If you don’t know that X is false, but your belief Y
would be unsupported if X were true, then you don’t
know Y.
5) Therefore, you don’t know any of the things that
depend on the fact that you’re not a brain in a vat.
6) If you’re a brain in a vat, then everything else you
believe is false.
7) Therefore, you don’t know any of those things.
8) Therefore you don’t know anything at all.
An Argument for Skepticism:








1) You have no evidence that you’re not a “brain in a
vat.” (Is this true? What evidence might you offer?)
2) If you have no evidence for X, then you don’t know X.
3) Therefore, You don’t know you’re not a brain in a vat.
4) If you don’t know that X is false, but your belief Y
would be unsupported if X were true, then you don’t
know Y. (Is this a questionable premise?)
5) Therefore, you don’t know any of the things that
depend on the fact that you’re not a brain in a vat.
6) If you’re a brain in a vat, then everything else you
believe is false.
7) Therefore, you don’t know any of those things.
8) Therefore you don’t know anything at all.
Skepticism:

Skepticism: We do not have knowledge of
anything at all.
Epistemology:
Theory of Knowledge
What is ‘knowledge?’ What is it to know
something?
 What does it mean to say that a belief is
‘justified?’
 What can we know?

We might start by listing the things we
believe:
Knowledge and Belief

We have a vast collection of beliefs, and some of them are false:
Some people believe that astrology can inform us about our futures.
…mind is constituted by the physical operation of the brain.
…mind is soul, an entity separate from brain activity that will survive the
death or our bodies.
…the universe is ultimately describable in terms of physical laws.
…a full description of the universe will include magic and super-natural
entities.
…aliens from outer space are in contact with human beings.
…human beings are the product of natural evolutionary selection.
…there is a God who created everything and who cares about us.
…human beings will make settlements on Mars.
…human beings are more likely, in the next millenium, to deplete the
earth of its resources and destroy the ecosystems on which we depend
for our lives.

Sifting and sorting: We don’t agree on all of these (at least, it’s unlikely
that we do.) Those beliefs about which we're less certain are less likely to
count as knowledge than those we're more certain of. Are there any
beliefs of which we are absolutely certain?
Knowledge and Belief
We believe many things.
 Not all of the things we believe are things
we know.


Among the things I believe, which are the
things I know?


Sextus?
Descartes?
Knowledge and Belief

Among the things I believe, which are the
things I know?

Hypothesis: The things I know are the
beliefs that are true.

Problem: What if I have true beliefs by
accident or for bad reasons?
Knowledge: Platos’s Analysis

Plato, Euthyphro: Knowledge is Justified
True Belief.

A person S knows a proposition P If and
only if:
1) S believes P
2) S is is justified in believing P
3) P is true
Knowledge: Platos’s Analysis

A person S knows a proposition P If and only if:
1) S believes P
2) S is is justified in believing P
3) P is true
1a) What is belief?
(Mental attitude associated with accompanying
dispositions)
1b) What are the objects of belief?
(Propositions: Statements that can be true or false.)
2) When is belief justified?
(There are alternative theories of justification)
3) What is it for a proposition to be true?
(There are alternative theories of truth)
Knowledge: Platos’s Analysis
JUSTIFICATION AND BELIEF:
The 'Why?' game...: at a certain point in a child’s
development, she gets the idea that there are reasons for
things, and start asking why.
Justification: A theory of the justification of beliefs must
provide us with a model of how to play the why game, or
as it is sometimes called, the justification game.
Skeptical Scenareos
Sextus Empiricus' Trilemma
(Also called Agrippa’s Trilemma, after Agrippa the Skeptic. This is a
Modern Rendition):
1) We have knowledge only if our beliefs are justified.
2) 'justification' can take three possible forms:
A) We justify our total belief set by reference to some
foundational belief or set of such beliefs, which are not
themselves justified by any further beliefs.
B) Our beliefs mutually justify one another.
C) There is an endless regress of justifying reasons.
3) Not A: A foundational belief could not justify other beliefs unless it were
itself justified.
4) Not B: Circular justification is no justification at all.
5) Not C: An endless regress of reasons could not provide justification for
our first-level beliefs.
6) Therefore, we don't have knowledge.
Skeptical Question:
Do we know anything at all?
 If I might be dreaming, might be a brain in
a vat, might be systematically deceived by
an evil genius…
…then can I know anything?


Many epistemic theories, like that of
Descartes, are attempts to show that
skepticism is false, and that we can have
justified beliefs in spite of the force of
skeptical arguments.
A Coherent Skepticism?

Skepticism: The view that we don’t have any
knowledge.
“Nothing can be known, not even this.”
-Carneades ~214-129 BCE
“The skeptical dictum is like a purgative: when we
take it, the dictum itself is thrown up along with all
our other dogmatic beliefs.”
-Miguel de Montaigne
Sextus Empiricus:

Skepticism is an ability to place reasons in
opposition to one another, so as to achieve a
balance that leaves us free of dogmatic beliefs.

Is skepticism self-contradictory? The skeptic
claims we have no knowledge (?), but isn’t
making that claim a violation of the skeptical
imperative to avoid making positive claims?
Sextus, Epicurus, and Epictetus:

All three urge that philosophy can provide us with
peace of mind, and protect us from unhappiness.

Ataraxia- (Epicurus and Sextus) Freedom from worry,
created by passions or dogmatic convictions.

Apatheia (Epicurus, Seneca) Freedom from passions,
and the false beliefs that generate passions.

Acatalepsia (Sextus) The ability to withhold both
assent and denial from doctrines that are presented to
us for belief.
Sextus:
Goal of skepticism is freedom and peace
of mind.
 Skepticism is an ability to withhold assent,
that can be mastered with practice and
study.
 We exercise this ability by considering all
the evidence against a proposition
alongside the evidence for it.

Sextus Empiricus:
Q: Why is skepticism characterized as an
“ability?”
A: It would be inconsistent for a skeptic to
have a “doctrine,” since adherence to a
doctrine involves belief and commitment.
(Connect this with the common charge that
skepticism is inconsistent…)
A Coherent Skepticism?

Skepticism: The view that we don’t have any
knowledge.
“Nothing can be known, not even this.”
-Carneades ~214-129 BCE
“The skeptical dictum is like a purgative: when we
take it, the dictum itself is thrown up along with all
our other dogmatic beliefs.”
-Miguel de Montaigne
Sextus:

Question: In denying that we know
anything, is the skeptic denying
‘knowledge’ in the Platonic sense, or
merely denying that we have certainty
about things? (Fallibilism)
Sextus and the Modes:

The modes are methods we can use to
achieve the suspension of judgment
(aporea or acatalepsia) that allows us a
kind of freedom we would not have if we
were to submit to dogmatic beliefs.
Modes of Skepticism:
1) The same objects
don’t produce the
same impression in
different animals.
2) Differences between
individuals lead to
differences in
perception of the
way things are.
3) Different senses give
us very different
information about the
objects we perceive.
4) Differences in our
circumstances cause
things to appear
differently to us.
(sleep/wake,
drunk/sober)
Modes of Skepticism
5) When we perceive
objects from different
positions, they appear
different to us.
6) We perceive objects
in groups, and the
“admixture” of
different objects
causes each to be
perceived differently
by us.
7) When substances
are in different states,
they appear
differently to us.
(snow/water)
8) Our perception of
objects is relative to
ourselves and
circumstances. (?)
Modes of Skepticism
9) Our perception of
objects changes
depending on
whether we see them
frequently or seldom.
10) Ethical judgments
appear to be based
on custom, and
different people with
different backgrounds
make different
judgments.
Sextus’s Instruction:
Whenever you are tempted by dogmatism, line
up reasons for and against the proposition until
they balance out.
 At this point, you will be free from convictions
(acatalepsia) having lost the propensity to
dogmatic adherence.
 In this state, you will be free trouble (in a state
of ataraxia) since we are only bothered when
our dogmatic convictions or judgments are
thwarted by the world.

Compare Skepticism and Stoicism:

Skeptics and stoics (and Epicureans too) agree that
our goal should be to free ourselves from troubles
arising from false beliefs.

While the stoics recommend extirpation of desires
and aversions, the Skeptics recommend extirpation
of dogmatic convictions.

The stoics agree that disturbances (desires and
aversions) arise from false beliefs. But they do not
recommend eliminating our beliefs.
Skeptical Ataraxia?

Abandoning dogmatic convictions will
leave us free and happy: we will be
undisturbed by things that disturb other
people. Their disturbance rests on a
mistake: they have allowed themselves to
believe where they should instead have
withheld belief and judgment.
Knowledge and Belief:
Descartes’s Problem

Descartes's Problem: How can I have
knowledge of anything, and which are the things
I know?

Sifting and sorting: Those beliefs about which
we're less certain are less likely to count as
knowledge than those we're more certain of. Are
there any beliefs we're absolutely certain of?
Knowledge and Belief:
Descartes’s Problem

DF of "undermining:" A proposition P undermines another
proposition Q just in case the truth of P would be good
evidence either (i) that Q is false, or (ii) that our reasons for
believing Q are not good reasons for believing Q.

Proposed Principle for Negative Justification: Take any
propositions P and Q where P undermines Q. If you have no
evidence that P is false, then you are not fully justified in
believing Q.

But: If you have no evidence that the “Demon hypothesis” is
false, then you are justified in believing none of the things that
would be undermined by this hypothesis.
Knowledge and Belief:
Descartes’s Problem

Descartes, Meditation I: The Dream Argument
1) In Meditation 1, Descartes believes that he is sitting
before a fire.
2) But if Descartes is in bed dreaming, then he's not
before a fire.
3) Descartes argues that he has no evidence (or
inadequate evidence) to justify his belief that he's not
dreaming.
4) So he doesn't know that he's not dreaming.
5) So he doesn't know that he's sitting before a fire.
DESCARTES: Meditations on
First Philosophy

Meditation One: Introduces Skeptical Problem,
Method of Doubt, distinguishes among different
sources of belief.

The Project: Wholesale reconstruction of a
belief system: Descartes wants to tear it to the
ground and build it back from solid foundations.
DESCARTES: Meditations on
First Philosophy

THE SKEPTICAL PROBLEM:

The starting point: recognition that many
previously held beliefs are either false or
unfounded. We need, he believes, a firm
foundation on which to place our knowledge, to
insure that our beliefs will be true.
DESCARTES: Meditations on
First Philosophy

Method of Doubt: Test beliefs according to
their "doubtability." If I can doubt one belief, but I
cannot doubt another, then surely my belief in
the second is firmer than my belief in the first.
For the moment, Descartes recommends that I
admit only those truths (if any) which I can
immediately perceive clearly and distinctly. Any
others whose truth I can derive from this basic
set will also be justified.
DESCARTES: Meditations on
First Philosophy

First Possible Way Out: Foundationalism: A
person is justified in holding a belief only if it is
either self evident, or is directly or indirectly
inferred from self evident propositions by selfevident principles of inference.

A proposition is self evident(df) just in case
believing that it is true is sufficient for knowing
that it is true. [Some philosophers have doubted
that there are any self evident propositions.]
DESCARTES: Meditations on
First Philosophy

Two Potential Problems for Foundationalism:
[These two are inconsistent with one another.
Do you see why?]

1) Perhaps there are no self-evident
propositions.
2) Perhaps there are some self-evident
propositions, but they are inadequate since they
provide us with no conclusive argument against
the skeptic.

DESCARTES: Meditations

CATEGORIES OF BELIEFS: Rather than examining each
belief in turn, (there are just too many) Descartes categorizes
his beliefs:
1) Blfs deriving from the senses. (Undermined by Dream
argument) (But the images composing my dream must have
their source somewhere-- there must exist some basic source
of this material I dream about... no? But what that basic source
may be is quite mysterious. Do I know that it mightn't be me?)
2) Blfs about empirical science have the same status as other
blfs deriving from the senses.
3) Blfs about "simple and universal" things (math & Logic)
Descartes finds that he can even doubt these...(Perhaps I get
confused whenever I add 2 and 2) (139.2)
DESCARTES: Meditations on
First Philosophy

ON THE EVIL GENIUS HYPOTHESIS:
Don't misunderstand: Descartes doesn't believe
that there is an evil demon, he rather considers
whether he has any evidence which would
enable him to prove that there is not one. The
evil demon hypothesis is one way to call into
question the justification of beliefs which derive
from the senses: it is a potential defeater for
many of the things we think we know.
DESCARTES: Meditations on
First Philosophy

Meditation One ends as it starts: with
unresolved doubts. It seems, at the end, that the
demon hypothesis provides a potential reason
for doubting just about anything. However,
Descartes (like Hume later) finds that he cannot
maintain skepticism: See p. 63: "But this
undertaking is arduous and a certain laziness
brings me back to my customary way of living."
DESCARTES: Meditations on
First Philosophy

One Kind of Objection: We don't have the technology
to envat people, and there isn't an evil genius... In sum,
the evil demon hypothesis is just not true.

Response: This objection is a non-starter since it begs
the question. Descartes never claimed that there is an
evil genius (nor did I claim that we are really envatted
brains). The point is to sift among our beliefs to find
those that are more securely justified than others. The
evil demon hypothesis is not true, but it is conceptually
possible (That is, thinking about it doesn't involve us in
any contradictions.)
DESCARTES: Meditations on
First Philosophy

Descartes and Skepticism: if we can find a
foundation for our belief system which is both
1) self evidently true, and
2) sufficiently powerful to enable us to deduce
that our perceptual beliefs are true, THEN we
could escape the skeptical argument. Is there
such a foundation?
DESCARTES: Meditations on
First Philosophy

ON TO MEDITATION TWO!



Descartes DISCOVERS a self-evident belief.
Descartes ARGUES that some of his beliefs
could not have originated with him.
Descartes PROVES (?) that God exists and
that God is not a deceiver.
DESCARTES: Meditations on
First Philosophy

Cogito: Consider the proposition 'I exist.'

Apply method of doubt: If there is any conceivable circumstance in
which it could SEEM TO ME that I exist, and yet I could be wrong,
then the proposition 'I exist' can be doubted. Is there such a
circumstance? Demon world is the most complete hallucination
imaginable. If I couldn't be wrong in the demon world, then I couldn't
be wrong at all.
But in the demon world I must exist, since there is an 'I' to be
deceived.
Therefore I know that I exist any time I stop to consider the question.

"Cogito Ergo Sum." (I think therefore I am.)
DESCARTES: Meditations on
First Philosophy

Descartes’s Foundational Belief: “I exist.”
1) I know X only if I perceive that clearly and distinctly
that X is true, such that it is impossible for me to doubt
X.
2) Query: Can I doubt my own existence.
3) For me to doubt my existence, there must be a ‘me’ to
do the doubting.
4) Any time I doubt my existence, I can clearly and
distinctly understand that I must exist.
5) I can’t doubt my own existence.
6) I know the proposition “I exist.”
DESCARTES: Meditations on
First Philosophy

"Cogito Ergo Sum." (I think therefore I am.)

How far will this get us?
Descartes has argued that the proposition "I
exist." is self evident. But is it powerful enough
that it can support my knowledge of the external
world? Can this help me out of the vat?
DESCARTES: Meditations on
First Philosophy

Descartes and Skepticism: if we can find a
foundation for our belief system which is both
1) self evidently true, and
2) sufficiently powerful to enable us to deduce
that our perceptual beliefs are true, THEN we
could escape the skeptical argument. Is there
such a foundation?
DESCARTES: Meditations on
First Philosophy

"Cogito Ergo Sum." (I think therefore I am.)

Question: What is this thing (ME) whom we know to exist?
Am I my body? Not in the demon world, where I still exist...

I am a thing that thinks. That's all I know for sure.
“I am something that doubts, affirms, understands, denies, wills,
refuses, imagines and senses.”

In fact, what I know is that I am a thing that has ideas.
Knowledge and Belief:
Motivating Skeptical Doubts

DF of "undermining:" A proposition P undermines another
proposition Q just in case the truth of P would be good
evidence either (i) that Q is false, or (ii) that our reasons for
believing Q are not good reasons for believing Q.

Proposed Principle for Negative Justification: Take any
propositions P and Q where P undermines Q. If you have no
evidence that P is false, then you are not justified in believing
Q.

Proposal: The “demon hypothesis” is an underminer for all
empirical beliefs. So if (1) you accept this proposed principle,
and (2) you have no evidence that the demon hypothesis is
false, then you must be a skeptic about all empirical beliefs.
Another ProblemKnowledge and Belief:
Is Justified True Belief ‘Knowledge?’

Example: I have on my car a sticker that says "Oberlin
College." People who see this sticker usually form the belief
that I graduated from Oberlin college. This belief is justified,
since the sticker is good evidence that I went to Oberlin. This
justified belief is true, since I did attend Oberlin. But is it
knowledge?

Problem: The sticker was on the car when I bought it (used),
and I didn't put it there. If people knew this, it would
undermine their belief that I went to Oberlin college, by
showing that their reason for believing that I did was not a
good reason.

Question: If you don't know that the sticker was on my car
when I bought it, is your belief that I went to Oberlin College
justified?
Knowledge and Belief: The Gettier Problem
1) John regards the Oberlin sticker on Clark’s car as
evidence that Clark went to Oberlin college.
2) John’s belief that <Clark went to Oberlin College> is
based on the fact that he saw an Oberlin sticker on Clark’s
car.
3) This belief is justified (the reason is a good one), true.
(I did attend Oberlin)
4) But contrary to John’s belief, the sticker on Clark’s car is
not evidence that Clark went to Oberlin.
5) Therefore John does not ‘know’ that Clark went to Oberlin.
6) Therefore justified true belief is not knowledge.
(Reject 3? Find an additional criterion to add to JTB?)
Gettier Problem:

“One may BELIEVE P, be JUSTIFIED IN
BELIEVING P, and P may be TRUE, but
this is not enough: one’s belief must be
connected with the truth in the right way.

If I’m right by accident, then my justified
true belief is not knowledge.
Responses to the Gettier Prob:
1)
Look for a theory of justification that ties the
justification of a belief more strongly to the
conditions that render it true.
2)
Accept that JTB is not knowledge…
3)
Fallibilism: accept that knowledge can be
fallible.
4)
Skepticism: We don’t have any knowledge.
DESCARTES: Meditations on
First Philosophy

The Wax Example:
My idea of the wax remains the same while the
wax goes through drastic changes: it is the
same wax although its properties change when
it is melted or frozen. My senses do not give me
an understanding of the wax: I get different
sensory information as the wax changes, but my
idea of the wax itself persists over these
changes. So "perceiving the wax" is essentially
an act of the mind, not of the senses.
DESCARTES: Meditations on
First Philosophy

The Wax Example: My idea of the wax remains the same while the
wax goes through drastic changes: it is the same wax although its
properties change when it is melted or frozen. My senses do not
give me an understanding of the wax: I get different sensory
information as the wax changes, but my idea of the wax itself
persists over these changes. So "perceiving the wax" is essentially
an act of the mind, not of the senses.

Theory of Representative Ideas: Knowledge is a two-way
relationship between one's ideas and the objects in the external
world. We have internal access to our ideas, but not to the objects of
which they are ideas.
DESCARTES: Meditations on
First Philosophy

A Problem for Cartesian Foundationalism: The theory
of representative ideas leaves us trapped in the confines
of our own mind! Descartes has (perhaps?) found a
foundational belief, but is it powerful enough to respond
to the skeptic? Does it enable us to think ourselves out
of the vat? Unfortunately, even if we have certainty with
respect to the cogito and also to our first level sensory
beliefs (beliefs about the way things seem to us), we
cannot derive from these basic beliefs any statements
about the existence of external objects. We can't make it
out of the vat.
DESCARTES: Meditations on
First Philosophy

To respond to the skeptic, a
foundationalist must show two things:
1) There are self evident propositions, and
2) From these propositions we can derive
knowledge of empirical reality.

So Descartes needs some more
equipment: He needs GOD.
DESCARTES: Meditations on
First Philosophy

MEDITATION THREE: Concerning the Existence of
God

Method: Descartes has established that he exists as a
thinking thing. In the third meditation he undertakes to
examine the ideas that he finds in his mind, and to
consider their origin. "But here I must inquire particularly
into those ideas that I believe to be derived from things
existing outside of me." If he can deduce that these
ideas do nor originate in him, then he may conclude that
there is something external that is the origin of these
ideas.
DESCARTES: Meditations on
First Philosophy

DESCARTES ARGUMENTS CONCERNING THE
EXISTENCE OF GOD:

Argument from the Perfect Idea of an Infinite Being:
1) I have an idea of God which is the idea of a substance
that is infinite, independent, supremely intelligent, and
supremely powerful. [III.45-6]
2) As a finite and imperfect being, I cannot be the cause
of a perfect idea of an infinite substance. [III.45-6]
3) Only an infinite and perfect being could be the cause
of such an idea.
4) Therefore, there exists an infinite and perfect being
who is the cause of my idea.
DESCARTES: Meditations on
First Philosophy

Ontological Argument: (Meditation Five)
1) I have an idea of God.
2) The idea of God is the idea of a being that
has all perfections.
3) 'Existence' is a perfection. [That is, what
exists in reality is more perfect than what exists
only in the imagination.]
4) Therefore a being that has all perfections
must have 'existence.'
5) God exists.
DESCARTES: Meditations on
First Philosophy

Anselm's Version of the Ontological Argument:
1) I have an idea of God.
2) The idea of God is the idea of the greatest conceivable being.
3) A being that exists in reality as well as in the mind (in
imagination) is greater than a being that exists only in the mind.
4) Suppose that the Greatest Conceivable Being exists only in the
mind but not in reality.
5) Then we can conceive of a being that is even greater: one who
exists in reality as well as in the mind.
6) Then we can conceive of a being greater than the greatest
conceivable being-- but that would be a contradiction!
7) Therefore it is not the case that the greatest conceivable being
exists only in the mind but not in reality.
8) Therefore the greatest conceivable being exists in reality as well
as in the mind.
9) Therefore God exists.
DESCARTES: Meditations on
First Philosophy

Some Further Steps:
1) If there is a perfect being, then the evil
demon hypothesis is false.
2) Therefore my senses give me true
information about the world.
3) Therefore skepticism is false.
DESCARTES: Meditations on
First Philosophy

Physicalism: Mind and body are both
physical substances, and the
consequence of interaction of physical
particles and forces.

Dualism: Mind and body are different
substances that interact but which are
essentially different.
DESCARTES: Meditations on
First Philosophy

Mind and Body:

Descartes is a Dualist: he argues that mind and body are different,
separate substances. Here is one Cartesian argument for Dualism:

1) If one substance has a property P while another substance lacks
property P, then the two substances are not identical.
2) I can doubt the existence of my mind: my mind has the property
of 'dubitability'.
3) I can't doubt the existence of my body: my body lacks the
property of dubitability.
4) Therefore my mind is a different substance from my body.
DESCARTES: Meditations on
First Philosophy

Reservation: is 'dubitability' a property of
things or of thinkers? Perhaps premises
two and three say more about Descartes
thought processes than about the things
Descartes is considering.
For Physicalism:
Physical Evidence of Anasthesia
 Contemporary Science of Consciousness
presumes physicalism.
 Mind-Brain Identity and “Split Brain”
cases.

DESCARTES: Meditations on
First Philosophy

Final Issues in Cartesian Epistemology:

Does Descartes have a satisfactory response to the
skeptic? Unless one is satisfied with the proof of the
existence of God, one may conclude that Descartes has
escaped the skeptical conclusion only because he
accepted a bad argument. Few believe that any of the
philosophical arguments for God's existence is
conclusive; indeed James assumes that his listeners and
readers will already have recognized that the evidence
for the existence of God is inconclusive.
Descartes: Where from here…?

Does Descartes have a satisfactory response to the skeptic? Unless
one is satisfied with the proof of the existence of God, one may
conclude that Descart has escaped the skeptical conclusion only
because he accepted a bad argument. Few believe that any of the
philosophical arguments for God's existence is conclusive; indeed
James assumes that his listeners and readers will already have
recognized that the evidence for the existence of God is
inconclusive.

If this is right, where does it leave Descartes? Are we still in the vat?
Some people conclude that Descartes simply failed to provide a
convincing response to the skeptic. The meditations get the
epistemological project off the ground, but don't really take it beyond
the vat. Where does the argument go wrong? There are several
possibilities:
Descartes: Where from here…?
Conclusions from Descartes Discussion:
1) The negative principle of justification may just be too strong a
condition to place on knowledge. Perhaps this principle should be
rejected. [Many (most!) contemporary epistemologists would reject it.]
2) Some attribute Descartes failure to the representative theory of
ideas: Bertrand Russell argued that perception gives us immediate
contact with the world, and denies Descartes claim that we are only in
immediate contact with our ideas.
3) Some argue that Descartes' failure shows that foundationalism is
unacceptable. One might opt instead for a Coherentist or Pragmatist
account of the justification of belief. [James' opts for a pragmatist
solution. Other contemporary epistemologists hold that beliefs come in
systems and deny that it is circular for all beliefs to be justified by
reference to other fallible beliefs.
Descartes: Where from here…?

Some Non-Cartesian Alternatives:

Coherentism: There are no adequate foundations for knowledge, but we
can be justified in our beliefs provided that they cohere appropriately with
other of our beliefs. [Coherentists must then give a clear account of what
'coherence' means, and must respond to the objection that fiction may be
coherent. See Keith Lehrer Theory of Knowledge for a clear, contemporary
coherentist account of justification.]

Fallibilism: To know a proposition, it not necessary to have indubitable
certainty that it is true.

Most fallibilists would reject the Negative Principle of Justification. Most
contemporary epistemologists are fallibilists. Those epistemologists who
are not fallibilists are mostly skeptics. [I haven't done a survey, these are
my impressions.]