epistemology: knowledge, skepticism, and ignorance

Epistemology: Knowledge, Skepticism, and Ignorance

Clark WolfDirector of Bioethics Iowa State University

[email protected]

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?


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?


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 P2) S is is justified in believing P3) P is true

Knowledge: Platos’s Analysis A person S knows a proposition P If and only if:

1) S believes P2) S is is justified in believing P3) 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?


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.


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.


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.


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.


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 self-evident 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.]


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)


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.


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."


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 and Skepticism: if we can find a foundation for our belief system which is both

1) self evidently true, and2) 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?


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.


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’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.”



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 and Skepticism: if we can find a foundation for our belief system which is both

1) self evidently true, and2) 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?



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.


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.


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.


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.


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.


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 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.


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.


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.


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.


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.


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.


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 AnasthesiaContemporary Science of Consciousness

presumes physicalism.Mind-Brain Identity and “Split Brain”

cases.


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:


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.


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.]

epistemology: knowledge, skepticism, and ignorance

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