Monday, February 6, 2006 PHL 105Y

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Monday, February 6, 2006PHL 105Y

• For Wednesday, finish reading Saul Kripkes A
  Priori Knowledge, Necessity and Contingency
  (pages 249-257 in the Pojman)
• For tutorial this Friday, answer one of the
  following questions
• Explain Kripkes distinction between rigid and
  non-rigid designators, and give an example (of
  your own) of each.
• Kripke thinks that there is a possible world in
  which the words Hesperus and Phosphorus name
  two different heavenly bodies, but no possible
  world in which Hesperus and Phosphorus are
  different things. Explain.

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An extra essay question

• Your next essay is due Monday, February 13, 2006,
  in class.
• In addition to the posted topics (on Moore and
  Russell), heres a further topic to choose
• According to A. J. Ayer, to say that the world of
  sense-experience is unreal is to say something
  not even false but nonsensical. (152) Why does
  Ayer think so? How compelling are his arguments
  in support of this claim?

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Alfred Jules Ayer(1910-1989)

• Our selections are from
• Language, Truth and Logic
• (1936, revised 1946)

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Ayer on Ethics and Theology
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A useful distinction

• Ayer distinguishes between two types of
  proposition
• Synthetic (like Humes matters of fact)
• The Eiffel Tower is in Paris.
• White rats are sometimes kept as pets.
• Analytic (like Humes relations of ideas)
• Triangles have three sides.
• White rats are white.
• Q How would you classify ethical statements?

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Four kinds of ethical statement

• 1. Definitional. ANALYTIC
• Morally permissible means not forbidden.
• Murder is the immoral and deliberate
  termination of anothers life.
• 2. Descriptive. SYNTHETIC
• Most people feel guilty when they have done
  something morally wrong.
• Murder is considered worse than theft.
• 3. Exhortatory. NON-PROPOSITIONAL!
• Dont steal music.
• 4. Actual ethical judgments. NON-PROPOSITIONAL!
• Stealing music is wrong.

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Ayer on ethics

• What we do in making a moral judgment is express
  our feelings (we are not, for example, describing
  a special layer of reality the realm of moral
  truths we are not even describing our own
  feelings, or expressing propositions about those
  feelings that would be subjectivism)
• These expressions of feeling serve to arouse
  feelings in others, and to move them to action as
  well

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Ayer on God

• Ayer is convinced that there is no demonstrative
  proof of the existence of God
• (From what premises could one prove such a
  thing?)
• (Without starting from some set of premises, one
  can only prove conditional claims like If A then
  A)

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Ayer on God

• Could we prove the existence of God from some set
  of observations, for example, observations about
  the regularity of nature?

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Ayer on God

• Could we prove the existence of God from some set
  of observations, for example, observations about
  the regularity of nature?
• Ayer contends that efforts to do so will have the
  result that God Exists means nothing more than
  Nature is Regular (which is not what religious
  people wanted)

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Ayer on God

• If there is no way of proving the existence of
  God (or even of showing that Gods existence is
  probable), then the sentence God exists is
  meaningless
• How does this differ from agnosticism? (in which
  we say that the question of whether God exists
  lies beyond human knowledge)

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Ayer on God

• The person who expresses belief in God is not
  stating a proposition but this is not to say
  that his utterances are invalid or false
• Sentences expressing religious belief have no
  truth value, but could still have some expressive
  value they could serve to express some sense of
  awe or powerlessness about ones destiny

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Ayer on God

• According to Ayer, those who claim to have
  mystical religious experiences are revealing
  something meaningful about their own psychology,
  but if they cannot formulate their claims about
  God in empirically verifiable terms they are not
  saying anything meaningful about reality
• Ayer is convinced that claims about a
  transcendent God can never be made in empirically
  verifiable terms (transcendent beyond earthly
  experience)

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Saul KripkeA Priori Knowledge, Necessity and
Contingency

• (Selections from Naming and Necessity, 1980)

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Apriority and necessity

• A Priori is an epistemic term to know something
  a priori is to know it independent of experience
  (say, by pure logical deduction)
• opposite empirical, a posteriori
• Necessary is a metaphysical term if something is
  necessary it must happen it is so in all
  possible worlds
• opposite contingent

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Apriority and necessity

• A Priori is an epistemic term to know something
  a priori is to know it independent of experience
  (say, by pure logical deduction)
• Necessary is a metaphysical term if something is
  necessary it must happen it is so in all
  possible worlds
• Q1 Is everything necessary knowable a priori?
• Q2 Is everything known a priori necessary?

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Apriority and necessity

• Logical and mathematical truths are necessary (if
  Goldbachs conjecture is true, it must be true
  there is no chance it could have turned out
  false)
• We can recognize this fact even if we dont know
  whether the Goldbach conjecture is true, and even
  if we never will (or even could not) know the
  truth of the conjecture a priori

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Apriority and necessity

• knowable a priori and necessary are NOT
  synonyms
• In fact, Kripke argues that some necessary truths
  are knowable only empirically, and some
  contingent truths are knowable a priori

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Analyticity

• Kripke takes analytic to mean true by virtue
  of meaning, and stipulates that analytic
  statements are necessarily true, or true in all
  possible worlds, and a priori.
• Examples
• A vixen is a female fox.
• Bachelors are unmarried.

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Certainty

• Certainty should not be confused with necessary
  or a priori (a long proof of a necessary truth
  can be a priori even if you feel uncertain about
  it)
• Kripke isnt much concerned with certainty here
  (lets set this notion aside for now)

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Possible worlds

• A possible world is a way things are or might
  have been
• There is a possible world in which it rained
  today, a possible world in which you were hit by
  a car last November, a possible world in which
  Paul Martin won the last election, even a
  possible world in which the NDP won the last
  election

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Possible worlds

• A possible world is a way things are or might
  have been
• There is no possible world in which circles are
  square. There is a possible world in which you
  are taller than you are now there is a possible
  world in which you are very athletic there is a
  possible world in which you parents named you
  Michael Jordan but there is no possible world
  in which you are Michael Jordan. (Why not?)

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Designators

• A rigid designator picks out the same object in
  all possible worlds
• A non-rigid designator picks out different
  objects in different possible worlds

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Designators

• A rigid designator picks out the same object in
  all possible worlds
• Examples Michael Jordan, Jack Layton, that guy
  right there
• A non-rigid designator picks out different
  objects in different possible worlds
• Examples the leader of the NDP in 2006 the
  tallest person taking PHL105
• Someone else could have been leader of the NDP in
  2006 no one other than Jack Layton could have
  been Jack Layton Jack Layton might not been
  called Jack Layton