Epistemology: Knowledge, Skepticism, and Ignorance

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Epistemology Knowledge, Skepticism, and
Ignorance
Clark Wolf Director of Bioethics Iowa State
University jwcwolf_at_iastate.edu
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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 dont 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)

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• 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 dont 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.

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Argument for Analysis

• Im 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 beingGod who is the cause of my
  perfect idea.

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• Im 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 beingGod 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)

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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 bodys existence my
  body is dubitable. I cant doubt my minds
  existence my mind is indubitable. Therefore
  mind and body are different substances.

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• 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 bodys existence my
  body is dubitable. I cant doubt my minds
  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, theyll have all properties in common.
  
• 4) But I can doubt my bodys existence my body
  is dubitable.
• 5) I cant doubt my minds existence my mind
  is indubitable.
• 6) Mind and body do not have all properties in
  common.
• 7) Therefore mind and body are different
  substances.

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Argument for Analysis

• According to Descartes, we cant know something
  unless we are so absolutely certain that it is
  true that we cant doubt it. But if we accepted
  this, we would be forced to conclude that we know
  nothing at all, or almost nothing. Its just
  wrong to say that we dont know something just
  because we can doubt that its true, or just
  because its possible that its false this isnt
  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 dont mean to
  indicate that I cant possibly be wrong about
  where I parked my bike, even if it turns out that
  Im a brain in a vat. So to know something isnt
  to be certain about it. So the Cartesian
  analysis of knowledge doesnt capture what we
  typically mean by knowledge.

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Argument for Analysis

• 1) According to Descartes, we cant know
  something unless we are so absolutely certain
  that it is true that we cant 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 isnt to be certain
  about it.
• 5) Descartes was wrong to believe that certainty
  is necessary for knowledge.

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SKEPTICISM Sextus Empiricus

• Plato distinguished knowledge from opinion,
  urging that we know only things we discover
  through reason.
• Aristotle and others call into question Platos
  claim that we know the things Plato thinks we
  know through reason.
• So what do we know?

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SKEPTICISM Sextus Empiricus

• Question What is knowledge?
• CLAIM You dont 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?

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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?

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An Argument for Skepticism

• 1) You have no evidence that youre not a brain
  in a vat.
• 2) If you have no evidence for X, then you dont
  know X.
• 3) Therefore, You dont know youre not a brain
  in a vat.
• 4) If you dont know that X is false, but your
  belief Y would be unsupported if X were true,
  then you dont know Y.
• 5) Therefore, you dont know any of the things
  that depend on the fact that youre not a brain
  in a vat.
• 6) If youre a brain in a vat, then everything
  else you believe is false.
• 7) Therefore, you dont know any of those things.
• 8) Therefore you dont know anything at all.

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An Argument for Skepticism

• 1) You have no evidence that youre not a brain
  in a vat. (Is this true? What evidence might
  you offer?)
• 2) If you have no evidence for X, then you dont
  know X.
• 3) Therefore, You dont know youre not a brain
  in a vat.
• 4) If you dont know that X is false, but your
  belief Y would be unsupported if X were true,
  then you dont know Y. (Is this a questionable
  premise?)
• 5) Therefore, you dont know any of the things
  that depend on the fact that youre not a brain
  in a vat.
• 6) If youre a brain in a vat, then everything
  else you believe is false.
• 7) Therefore, you dont know any of those things.
• 8) Therefore you dont know anything at all.

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Skepticism

• Skepticism We do not have knowledge of anything
  at all.

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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

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Knowledge and Belief

• We have a vast collection of beliefs, and some of
  them are falseSome 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 dont agree on all of
  these (at least, its 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?

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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?

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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?

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Knowledge Platoss 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

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Knowledge Platoss 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)

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Knowledge Platoss Analysis

• JUSTIFICATION AND BELIEF
• The 'Why?' game... at a certain point in a
  childs 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.

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Skeptical Scenareos

• Sextus Empiricus' Trilemma
• (Also called Agrippas 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.

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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?

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• 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.

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A Coherent Skepticism?

• Skepticism The view that we dont 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

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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 isnt making
  that claim a violation of the skeptical
  imperative to avoid making positive claims?

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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.

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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.

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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)

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A Coherent Skepticism?

• Skepticism The view that we dont 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

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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)

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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.

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Modes of Skepticism

• 1) The same objects dont 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)

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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. (?)

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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.

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Sextuss 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.

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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.

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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.

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Knowledge and Belief Descartess 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?

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Knowledge and Belief Descartess 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.

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Knowledge and Belief Descartess 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.

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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.

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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.

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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.

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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
  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.

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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.

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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)

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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.

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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."

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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.)

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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, 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?

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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.

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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.)

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DESCARTES Meditations on First Philosophy

• Descartess 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 cant doubt my own existence.
• 6) I know the proposition I exist.

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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?

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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, 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?

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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.

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Knowledge and BeliefMotivating 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.

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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?

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Knowledge and Belief The Gettier Problem

• 1) John regards the Oberlin sticker on Clarks
  car as evidence that Clark went to Oberlin
  college.
• 2) Johns belief that ltClark went to Oberlin
  Collegegt is based on the fact that he saw an
  Oberlin sticker on Clarks car.
• 3) This belief is justified (the reason is a
  good one), true.
• (I did attend Oberlin)
• 4) But contrary to Johns belief, the sticker
  on Clarks 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?)

67
Gettier Problem

• One may BELIEVE P, be JUSTIFIED IN BELIEVING P,
  and P may be TRUE, but this is not enough ones
  belief must be connected with the truth in the
  right way.
• If Im right by accident, then my justified true
  belief is not knowledge.

68
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 dont have any knowledge.

69
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.

70
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.

71
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.

72
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.

73
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.

74
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.45-62) As a finite and imperfect
  being, I cannot be the cause of a perfect idea of
  an infinite substance. III.45-63) 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.

75
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.

76
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.

77
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.

78
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.

79
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.

80
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.

81
For Physicalism

• Physical Evidence of Anasthesia
• Contemporary Science of Consciousness presumes
  physicalism.
• Mind-Brain Identity and Split Brain cases.

82
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.

83
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

84
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.

85
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.