Monday february 6 2006 phl 105y
Download
1 / 24

Monday, February 6, 2006 PHL 105Y - PowerPoint PPT Presentation


Monday, February 6, 2006 PHL 105Y. For Wednesday, finish reading Saul Kripke’s “A Priori Knowledge, Necessity and Contingency” (pages 249-257 in the Pojman) For tutorial this Friday, answer one of the following questions:

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Monday, February 6, 2006 PHL 105Y ' - richard_edik


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Monday february 6 2006 phl 105y l.jpg
Monday, February 6, 2006PHL 105Y

  • For Wednesday, finish reading Saul Kripke’s “A Priori Knowledge, Necessity and Contingency” (pages 249-257 in the Pojman)

  • For tutorial this Friday, answer one of the following questions:

  • Explain Kripke’s 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.


An extra essay question l.jpg
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), here’s 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?


Alfred jules ayer 1910 1989 l.jpg

Alfred Jules Ayer(1910-1989)

Our selections are from

Language, Truth and Logic

(1936, revised 1946)



A useful distinction l.jpg
A useful distinction

  • Ayer distinguishes between two types of proposition:

  • Synthetic (like Hume’s matters of fact)

    • ‘The Eiffel Tower is in Paris.’

    • ‘White rats are sometimes kept as pets.’

  • Analytic (like Hume’s relations of ideas)

    • ‘Triangles have three sides.’

    • ‘White rats are white.’

  • Q: How would you classify ethical statements?


Four kinds of ethical statement l.jpg
Four kinds of ethical statement

  • 1. Definitional. ANALYTIC

    • ‘Morally permissible’ means ‘not forbidden.’

    • ‘Murder’ is the immoral and deliberate termination of another’s 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!

    • Don’t steal music.

  • 4. Actual ethical judgments. NON-PROPOSITIONAL!

    • Stealing music is wrong.


Ayer on ethics l.jpg
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


Ayer on god l.jpg
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)


Ayer on god9 l.jpg
Ayer on God

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


Ayer on god10 l.jpg
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)


Ayer on god11 l.jpg
Ayer on God

  • If there is no way of proving the existence of God (or even of showing that God’s 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)


Ayer on god12 l.jpg
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 one’s destiny


Ayer on god13 l.jpg
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)


Saul kripke a priori knowledge necessity and contingency l.jpg

Saul Kripke:A Priori Knowledge, Necessity and Contingency

(Selections from Naming and Necessity, 1980)


Apriority and necessity l.jpg
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]


Apriority and necessity16 l.jpg
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?


Apriority and necessity17 l.jpg
Apriority and necessity

  • Logical and mathematical truths are necessary (if Goldbach’s 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 don’t 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


Apriority and necessity18 l.jpg
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


Analyticity l.jpg
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.


Certainty l.jpg
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 isn’t much concerned with certainty here (let’s set this notion aside for now)


Possible worlds l.jpg
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


Possible worlds22 l.jpg
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 youare Michael Jordan. (Why not?)


Designators l.jpg
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


Designators24 l.jpg
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”


ad
  • Login