Epistemology

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Epistemology

• Theory of knowledge and Truth

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EPISTEMOLOGY The theory of knowledge

• (1) What does it mean for a set of beliefs to be
  true? What kinds of truth are there?
• (2) How will we know when our beliefs are true?
  What are the criteria for having knowledge?

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Two Kinds of Truth

• Traditionally, there are two kinds of truth
• (1) NECESSARY
• (2) EMPIRICAL (or Contingent)

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NECESSARY TRUTHS

• A statement expressing a necessary truth cannot
  possibly be false. Examples
• All triangles have three sides.
• All bachelors are unmarried.
• No one who believes that God exists is an atheist.

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Necessary Truths

• The truth of a necessary truth does not depend on
  what the facts are like necessary truths are
  always true no matter what. Examples
• Can you ever find a bachelor who is married?
• Can you ever find a triangle that does not have 3
  sides?
• Is it possible to find an atheist who believes in
  God?

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Necessary Falsehoods

• We can say similar things about necessary
  falsehoods.
• Impossible to be true
• Their falsity does not depend on what the facts
  are like necessary falsehoods are always false
  no matter what

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Necessary Truths and theA Priori (a pre or e)

• A Priori prior to experience or independent of
  any experience of facts or states of affairs in
  the world.
• Necessary truths are often said to be true a
  priori, true independent of any particular facts.

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Necessary Truths andA Priori Truths

• It is also said that their poof (or
  justification) does not depend on any particular
  facts of the world.

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Necessary Truths andAnalytic Truths

• Necessary truths are sometimes called analytic
  truths
• Analytic truths are necessarily true because
• (1) The predicate is contained in the concept of
  the subject.
• (2) Denying the truth of the statement leads to a
  contradiction.
• (3) Contradictions are impossible and go against
  reason.

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Analytic Truths

• All sisters are female is an analytic truth
  because the predicate female is contained in
  the subject sister. Why? A sister is defined as
  being a female sibling. So All sisters are
  female says the same thing as All female
  siblings are female. The predicate is contained
  in the subject. It is easy to see that it would
  be a contradiction to say that not all female
  siblings are female. So All sisters are female
  is necessarily true and couldnt possibly be
  false.

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Analytic Truths

• Example Fathers are males.
• The concept male is in the concept of father
  (male parent).

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Analytic Truths

• Example All electrons are subatomic particles.
• An electron is by definition a certain type of
  subatomic particle. So the concept of a subatomic
  particle is contained in the concept of an
  electron.

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Empirical (or Contingent) Truths

• Empirical having to do with experience
  Contingent depending on experience
• A statement expressing an empirical truth is true
  in virtue of the facts. An empirical statement is
  empirical because its truth value (whether it is
  true or false) depends on what the world is like.

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Empirical (or Contingent) Truths

• They can be known to be true only after actually
  looking at (or knowing about) the facts of the
  world. It is possible for an empirical truth to
  be false because of the facts.
• We can say similar things about empirical
  falsehoods.

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Empirical (or Contingent) Truths

• Empirical Statement Microorganisms live on Mars.
  
• Empirical truth Over 5 billion people live on
  Earth.
• Empirical falsehood Germany won WWII.

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Empirical Truths andA Posteriori Truths

• A posteriori with experience or depending on
  experience of the facts
• Empirical truths are sometimes called a
  posteriori because empirical truths depend on
  the facts.

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Test A Priori and A Posteriori Are these
statements true or false?

• I can know a priori that all bachelors are
  unmarried.
• It is impossible to know a priori whether New
  York has more inhabitants than Mexico City.
• I can know a priori that there is life on other
  planets.
• All of mathematics is based on a priori reasoning.

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Test A Priori and A Posteriori Are these
statements true or false?

• Nobody can know through a priori reasoning that
  the Empire State building is the tallest building
  in the world.
• I can know a priori that is someone is shot to
  death, then somebody must have been a shooter.
• I can know a priori that a cube must have 12
  edges.
• I can know a priori that all swans are white.

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Empirical Truths andSynthetic Truths

• Empirical truths are sometimes called synthetic
  truths because the predicate of the statement is
  not contained in the subject but is connected to
  it through experience.
• Example My car has more than 1 gallon of gas in
  it.
• Example The door to this room is shut.
• Example George Bush is president.

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Test Analytic or Synthetic Claims?

• All pencils and pens are writing utensils.
• Electrons are the smallest physical particles in
  the universe.
• More than 20 million people died of AIDS last
  year.
• There are more heterosexual humans than
  homosexual humans.
• Earthquakes are natural disasters.

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Test Analytic or Synthetic Claims?

• Dogs and cows are both animals.
• Texas is larger than Oklahoma.
• The average lawyer makes more than 70,000 a
  year.
• All solid spheres have one surface.

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Test Necessary or Empirical Claim?

• If one multiplies any natural number by 2, the
  resulting number is even.
• The income of the average worker in the US is
  higher than the income of the average worker in
  Europe.
• Every state must have some form of government.
• Every event has a cause.
• If any nation should ever use nuclear weapons
  again, then millions of people will die.

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Test Necessary or Empirical Claim?

• Every recession in the economy is eventually
  followed by an economic recovery.
• If a person freely performs an action, then the
  person can be held responsible for the action.
• Sugar is sweet.
• All human beings have the same fundamental
  rights.
• All cats are animals.

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Test Necessary or Empirical Claim?

• The moon moves around the earth.
• All US presidents are male.
• The US withdrew from Vietnam in 1975.
• If Frank has more than 2 sisters, then he has at
  least three siblings.
• There are infinitely many prime numbers.
• In order to graduate from Northwestern
  University, one has to take at least 3 English
  classes.

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Necessary and Empirical Truths

• Necessary Truths
• Analytic
• A priori
• Empirical (or contingent) Truths
• Synthetic
• A posteriori

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Knowledge Three Kinds

• (1) Knowing how
• (2) Knowledge by acquaintance
• (3) Knowing that
• In philosophy, we are almost always concerned
  with (3), the knowing-that kind of knowledge.

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Knowing How

• (1) Knowing how (competence knowledge, skill
  knowledge) This has to do with knowing how to do
  something. For example, I know how to ride a bike.

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Knowledge by Acquaintance

• (2) Knowledge by acquaintance This is knowledge
  that one has when one knows something or someone
  directly. For example, I know my friend Jack by
  having been in direct contact with him.

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Knowing That

• (3) Knowing that (propositional knowledge,
  descriptive knowledge) This is knowledge that
  something is the case. For example, I know that
  the earth has one moon.
• In philosophy, we are almost always concerned
  with (3), the knowing-that kind of knowledge.

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Test Knowledge (1) how, (2) by acquaintance, or
(3) propositional?

• I know exactly how you feel about her death.
• 224, I know that for a fact.
• I used to know Peter very well but in recent
  times we have grown apart.
• Im not afraid to cheat on my exams because I
  know how to cheat without getting caught.

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Test Knowledge (1) how, (2) by acquaintance, or
(3) propositional?

• If only I knew more about the Vietnam war.
• My father used to be the smartest man. Now, he
  has Alzheimers, and he doesnt know anything
  anymore.
• You might know something that is in your
  accounting book, but this doesnt mean that you
  know anything about how to run an accounting
  firm.

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Knowledge Does Believing Strongly Give Us
Knowledge?

• Can believing strongly that something is true,
  make it true?

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Knowledge

• Simply believing strongly that something is true
  in no way establishes that it is true. Strong
  belief is not the key to having knowledge. Do you
  agree?

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Knowledge Does Having a True Belief Give One
Knowledge?

• Suppose you have a true belief. Do you have
  knowledge? Do you know that this belief is true?

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Knowledge True Belief Is Not Enough for Knowledge

• Suppose Mike is on the quiz show Who Wants To Be
  a Millionaire? He is asked the name of the Greek
  city-state that defeated the Persians in the
  battle of Marathon. Mike doesnt know ancient
  Greek history or the battle of Marathon. But he
  believes that Athens is the answer and selects
  it. It turns out that Athens is the correct
  answer. But does Mike know that it is the correct
  answer? No, he is merely guessing.

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Knowledge What is needed for it?

• When a belief is appropriately linked to truth,
  then the belief counts as knowledge. But what
  exactly is this link, and what is knowledge? Can
  you think of some beliefs that you have that
  count as examples of knowledge?

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Knowledge Classical Definition

• Someone S knows that P if and only if
• (1) S believes that P is true
• (2) P is true
• (3) S is justified in believing that P is true
• We have to add justification. One has to have
  reasons or evidence of some kind to establish
  that the belief is true. Knowledge is justified
  true belief.

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Can you KNOW any of the following? (Can you
justify any?)

• I know that I have two hands.
• I know that president Bush will never get
  divorced.
• I know that other people experience the smell of
  coffee just like I do.
• I know that Joe Montana is a better quarterback
  than John Elway.
• I know that water is H20.

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Can you KNOW any of the following? (Can you
justify any?)

• I know that the Bible contains Gods word.
• I know that killing people is wrong.
• I know that George Washington was a US president.
• I know that dinosaurs existed on the earth in the
  past.
• I know that there are at least 8 planets in our
  solar system.
• I know that Michael Jackson is an emotionally
  troubled man.

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Gettier Cases

• Recently, epistemologists have challenged the
  classical view of knowledge as justified true
  belief. Special cases seem to show that having a
  justified true belief is not sufficient for
  having knowledge. These special cases are called
  Gettier Cases (after the philosopher who first
  introduced them).

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Example Gettier Case

• Imagine that you and another person go to
  interview for a job at Wal-Mart. After your
  interview, they call you into the office and tell
  you that they are going to hire the other person.
  They let you go. As you leave, you see the other
  person holding two quarters, which he puts into
  his pants pocket. You think to yourself The
  person hired for this Wal-Mart job has fifty
  cents in his pocket. And this belief is also
  justified. You go home, but the telephone rings.
  They tell you that they have hired you for the
  job. It just so happens that you have fifty cents
  in your pants pocket. So your belief that the
  person hired for the job has fifty cents in his
  pocket was a justified true belief. But we
  couldnt say that you had knowledge, could we?

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Epistemic Justification

• What can we know and how much do we know? To help
  answer these questions, we need a theory of
  epistemic justification. Knowledge is justified
  true belief. If we can determine when and how our
  beliefs are justified, then we can determine the
  scope and limits of our knowledge. In broad
  strokes, there are three main theories about
  epistemic justification
• (1) Skepticism
• (2) Empiricism
• (3) Rationalism

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Skepticism

• Skepticism says that there is no adequate
  justification for our beliefs, so we can never
  attain knowledge. We can have beliefs, but no
  knowledge.
• Global Skepticism denies that there can be
  knowledge of any kind about any subject matter.
  Not many people hold global skepticism, but it is
  hard to defeat in conversation
• Local Skepticism denies that we can have
  knowledge regarding some subject matters, but not
  all, or that some methods of justification are
  not reliable (like reading fortune cookies,
  astrology, psychic hotlines, alternative
  medicine, or TV news).

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Empiricism

• An empiricist holds that our beliefs can be best
  justified in light of the evidence we receive
  from our senses. We therefore can know something
  if we can justify it with respect to what we see,
  hear, and feel about the world. According to
  empiricism, natural sciences like physics,
  chemistry, and biology produce the most reliable
  knowledge. We can know something if we can
  justify it through what we can experience through
  our senses.

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Empiricists

• John Locke (1632-1704)
• Bishop Berkeley (1685-1753)
• David Hume (1711-1776)
• John Stuart Mill (1806-1873)
• Bertrand Russell (1872-1970)
• Logical Positivists A.J. Ayer (1910-1989)
• William James (1842-1910)

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Rationalism

• A rationalist believes that our beliefs can be
  best justified in light of rational evidence, not
  sensory evidence. We can know something if it
  appears true in the light of reason, not our
  senses. According to rationalism, mathematics and
  logic provide the most reliable knowledge.

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Rationalists

• Plato
• Rene Descartes (1556-1650)
• Baruch Spinoza (1632-1677)
• Gottfried Leibniz (1646-1716)

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Rationalism Descartes Meditations

• Purpose He wants to find a certain and
  indubitable (beyond doubt) foundation on which to
  build all scientific knowledge.
• All knowledge must be based on
• Intuition The mind can grasp clear and distinct
  ideas with certainty.
• Deduction Using deduction, one can derive new
  truths from other truths that are known to be
  true by intuition.

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Rationalism Descartes Meditations

• I was convinced that I must once for all
  seriously undertake to rid myself of all the
  opinions which I had formerly accepted, and
  commence to build anew from the foundation, if I
  wanted to establish any firm and permanent
  structure in the sciences.
• Descartes begins with radical skepticism, radical
  doubt.

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Rationalism Descartes Meditations

• I have delivered my mind from every care and
  am happily agitated by no passions and since I
  have procured for myself an assured leisure in a
  peaceable retirement, I shall at last seriously
  and freely address myself to the general upheaval
  of all my former opinions.

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Rationalism Descartes Meditations

• It is not necessary that I should show that all
  of these former opinions are false.
• If I am able to find in each one some reason to
  doubt, this will suffice to justify my rejecting
  the whole.

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Rationalism Descartes Meditations

• the destruction of the foundations brings
  with it the downfall of the rest of the edifice.
• I shall only in the first place attack those
  principles upon which all my former opinions
  rested.

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Rationalism Descartes Meditations

• it is sometimes proved to me that the senses are
  deceptive, and it is wiser not to trust entirely
  to anything by which we have once been deceived.
• although the senses sometimes deceive us there
  are yet many things known through the senses
  that we cannot reasonably doubt.
• For example, there is the fact that I am here,
  seated by the fire, attired in a dressing gown,
  having this paper in my hands and other similar
  matters.

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Rationalism Descartes MeditationsThe Dream
Argument

• I must remember that I am a man, and that
  consequently I am in the habit of sleeping.
• how often has it happened to me that in the
  night I dreamt that I found myself in this
  particular place, that I was dressed and seated
  near the fire, while in reality I was lying
  undressed in bed!
• there are no certain indications by which we may
  clearly distinguish wakefulness from sleep.

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Rationalism Descartes Meditations

• Arithmetic, Geometry and other sciences of that
  kind contain some measure of certainty and an
  element of the indubitable
• For whether I am awake or asleep, 2 3 5, and
  the square can never have more than 4 sides, and
  it does not seem possible that truths so clear
  and apparent can be suspected of any falsity or
  uncertainty.

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Rationalism Descartes MeditationsThe Evil
Genius Argument

• I shall then suppose some evil God-like genius
  has employed his whole energies in deceiving
  me.
• how do I know that Im not deceived every time
  that I add two and three, or count the sides of a
  square .
• I shall consider that the heavens, the earth,
  colors, figures, sound, and all other external
  things are naught but the illusions and dreams of
  which this genius has availed himself in order to
  lay traps for my credulity.

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Rationalism Descartes MeditationsCogito Ergo
Sum

• I shall ever follow in this road until I have
  met with something which is certain.
• I myself, am I not at least something?
• I myself exist merely because I thought of
  something
• Let the evil genius deceive me as much as he
  will, he can never cause me to be nothing so long
  as I think that I am something.
• We must come to the definite conclusion that
  this proposition I am, I exist, is necessarily
  true each time that I pronounce it, or that I
  mentally conceive it.

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Rationalism Descartes Meditations

• Descartes has shown that he exists as a mind. But
  he has to prove that there is an external world
  of bodies, too.
• First, he proves that God exists. Then he argues
  that the external world must exist because if it
  didnt, then God would be a deceiver. But God
  cant be a deceiver. So the external world
  exists.
• In this way, Descartes establishes an absolutely
  certain foundation for all scientific knowledge
  and begins building that knowledge up into a
  complete system.

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Theories of Truth

• Correspondence Theory
• A belief is true if it corresponds to some fact
  or real object
• Coherence Theory
• A belief is true if it coheres with a body of
  other statements that we take to be true
• Pragmatic theory
• A belief is true if it works for you. It helps
  you understand things and leads you to successes.

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Correspondence Theory

• Plato Truth is obtained by grasping the Forms.
• Logical Positivists A.J. Ayer