A.J. Ayer The Elimination of Met

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					Logical Positivism


  Ayer on The A Priori
            Language, Truth and Logic



                      LOGICAL
                     POSITIVISM




Ayer’s report on what the Vienna Circle was doing, for English-
speaking folk.
                    What I’m going to do

• The Vienna Circle and its historical antecedents, its influence on
  analytic philosophy

• The Logical Positivist program, including

    – The Verification Principle and anti-metaphysical agenda

    – Philosophy as analysis: the quest for an ideal language

    – Commitment to phenomenalism

• Ayer on the A Priori

    – The analytic/synthetic distinction

    – Math and logic as ―tautologous‖
    Logical Positivism is a form of Empiricism
                        Thought is an
                     independent source
                        of knowledge.

                                            No! All factual
                                          knowledge comes
                                           from experience




      Rationalist                                             Empiricist

   It is characteristic of an empiricist to eschew metaphysics, on the
   ground that every factual proposition must refer to sense
   experience.

• Problem: how to account for necessary truths, including notably
  truths of mathematics and logic since it’s always possible in principle
  to falsify empirical generalizations.

• Ayer needs an account that will get rid of bad metaphysics without
  throwing out good mathematics.
            The Elimination of Metaphysics

• The Metaphysical Thesis: philosophy affords us knowledge of a
  reality transcending the world of science and common sense.

    – The Absolute enters into but is itself incapable of evolution and
      progress. (Bradley)

    – Nothing noths (Heidegger)

• Ayer’s Thesis: talk about such a transcendent reality is, literally,
  meaningless.

    – ―The function of philosophy is wholly critical‖ (contra Descartes)

    – ―Philosophy leaves everything as it is.

• The business of philosophy is analysis: ―the propositions of
  philosophy are…linguistic in character.‖
               We’re deluded by language

• E.g. the Fido-Fido theory of meaning: every noun names an object

• The Wino’s Paradox

    – Nothing is better than champagne

    – Thunderbird is better than nothing

    – Therefore Thunderbird is better than champagne

• Challenge: translate this argument into the
  language of predicate logic!

• Russell showed that the correct analysis
  of the logical form of these claims blocks
  the inference.
    Not your grandmother’s empiricism!

• The old Kantian attack on metaphysics was
  epistemological

    – Starting from experience all we can validly infer are
      further facts about experience.

• But the metaphysician can just claim access to
  transcendent reality via ―intellectual intuition‖

• Even if ―intellectual intuition‖ is baloney, this
  doesn’t show his conclusions are false…
  just that we can’t know whether they’re
  true or false.

• Logical positivists hold that metaphysical
  claims are neither true nor false but literally
  meaningless—i.e. nonsense.
     The Business of Philosophy is Analysis

• Paraphrasing away: Russell’s ―On Denoting‖ as the paradigm of
  analysis

    – Nothing is better than champagne
      ~ (∃x) (x is better than champagne)

• Artificial languages as means to accomplish analysis

• Logical constructions and inferred entities

    – ―We are all phenomenalists now.‖

• Analysis is concerned with cognitive content understood in terms of
  equivalence and entailment relations.

• Goal: the elimination of metaphysics
Is denying metaphysics is just more metaphysics?

    Wittgenstein says, "in order to draw a limit to thinking, we should
    have to think both sides of this limit," a truth to which Bradley gives a
    special twist in maintaining that the man who is ready to prove that
    metaphysics is impossible is a brother metaphysician with a rival
    theory of his own.


 • So we can’t adopt Kant’s strategy of arguing that metaphysics is
   psychologically impossible since that would mean showing that
   there are metaphysical truths that we couldn’t understand—which is
   itself a metaphysical claim


 • To avoid just doing more metaphysics we have to show that
   metaphysical claims are meaningless.


 • So we adopt the Verification Principle as a criterion for
   meaningfulness.
               The Verification Principle

   To state the circumstances under which a proposition is true is the
   same as stating its meaning. (Schlick)

   A sentence is factually significant to any given person, if and only
   if, he knows how to verify the proposition which it purports to
   express.

• Example: ―There’s a skunk living in the crawl space under my
  house.‖

• I know what experiences would verify the proposition this
  sentence purports to express—for example:

                » Every few days I experience a characteristic smell.

                » My dog was barking like crazy, then ran into the
                  house yelping and whining—and stinking.
  Bad Metaphysics flunks the Verification Test

• Challenge: what experiences would verify—or falsify—the following
  metaphysical claims?

   – The Absolute enters into but is itself incapable of evolution and
     progress. (Bradley)

   – Nothing noths (Heidegger)

• Problem: what experiences would verify

   – claims about laws of nature

   – claims about the past, e.g. Lucy had exactly
     four children
Practical Verifiability & Verifiability in Principle

• Propositions about the past can’t now be conclusively verified or
  falsified but we can say what sorts of experiences would verify or
  falsify them.


• Verifiability doesn’t have to be feasible--only possible in principle


    – There are mountains on the other side of the moon


    – Lucy had exactly four children


• We require only verification in principle: we have to be able to say
  what sort of experience would verify of falsify.


• So propositions about the past are ok.
              Strong and Weak Verification

• A proposition is verifiable in the strong sense iff its truth could be
  conclusively established in experience.

• A proposition is verifiable in the weak sense iff it is possible to
  render it probable.

• All we require for meaningfulness is weak verifiability

• So laws of nature, which are merely very, very, very, very, very
  highly probable are ok.

• Only a ―tautology,‖ a claim which has no factual content and conveys
  no information about the world, can be anything more than a
  probable hypothesis.

    – Example: Either today is Tuesday or today is not Tuesday.
                What’s hot and what’s not

   Sense                               Nonsense


• Ordinary empirical claims, e.g.   • Metaphysics, e.g. ―nothing
  ―there’s a skunk living in my       noths.‖
  crawlspace.‖

                                    • Theology, e.g. ―God exists.‖
• Claims about remote times and
  places, e.g. ―Lucy had 4
  children.‖                        • Ethics, e.g. ―Torturing young
                                      children for fun is wrong.‖

• Laws of nature, e.g. ―under
  conditions found on earth,        • Aesthetics, e.g. ―St. Pauls,
  water freezes at 32 F.‖             London, is one of the 10 most
                                      beautiful buildings in Europe.‖
   Throwing out the baby with the bathwater?

• The elimination of metaphysics: mission accomplished.

• Theology as nonsense: no problem.

• Ethics (and aesthetics) can be reconstructed as expressive or
  prescriptive.

• But with math and logic…we have a serious problem.
             The Empiricist’s Math Dilemma

• The empiricist must deal with the truths of logic and mathematics in
  one of the two following ways: he must say either that they are not
  necessary truths, in which case he must account for the universal
  conviction that they are; or he must say that they have no factual
  content, and then he must explain how a proposition which is empty
  of all factual content can be true and useful and surprising.


                          Not
                       necessary          No factual
                        truths!            content!




         J. S. Mill                                    David Hume
                  Mill’s view rejected


                 2+2=4



                                 Lucky for Mill
                                 things aren’t
                                 nailed down.




The course of maintaining that the truths of logic and mathematics
are not necessary or certain was adopted by Mill. He maintained
that these propositions were inductive generalizations based on an
extremely large number of instances.
             Ayer goes with Hume’s Fork
―All the objects of human reason or enquiry may naturally be divided
into two kinds, to wit, Relations of Ideas, and Matters of fact. Of the
first kind are the sciences of Geometry, Algebra and Arithmetic...
[which are] discoverable by the mere operation of thought ... Matters
of fact, which are the second object of human reason, are not
ascertained in the same manner; nor is our evidence of their truth,
however great, of a like nature with the foregoing.‖ [Hume, Enquiry
Concerning Human Understanding]
                                necessary – a priori - analytic


                               contingent – a posteriori - synthetic


If we take in our hand any volume; of divinity or school metaphysics,
for instance; let us ask, Does it contain any abstract reasoning
concerning quantity or number? No. Does it contain any experimental
reasoning concerning matter of fact and existence? No. Commit it
then to the flames: for it can contain nothing but sophistry and
illusion. [Hume, Enquiry Concerning Human Understanding]
               Language, Truth and Logic

• Metaphilosophy: the function of philosophy and how it accomplishes
  its results

• Hume’s Fork: ―Tautologies‖ and factual claims

    – The a priori: math and logic

    – Factual claims: science and everything else

• Nonsense: ethics and theology

• (Dis)solutions of traditional philosophical problems
    Kant: The Analytic/Synthetic Distinction

   In all judgments in which the relation of a subject to the
   predicate is thought … this relation is possible in two different
   ways. Either the predicate B belongs to the subject A as
   something that is (covertly) contained in this concept A; or B lies
   entirely outside the concept A… In the first case, I call the
   judgment analytic, in the second synthetic…I merely draw out
   the predicate in accordance with the principle of contradiction,
   and can thereby at the same time become conscious of the
   necessity of the judgment (Kant)

• Analytic sentences are true in virtue of language alone

• They’re a priori (knowable independent of experience) because
  they’re empty of factual content.

• They’re necessary because we don’t allow them to be false, e.g.

    – if the angles of a figure don’t add up to 180 degrees we don’t
      count it as a Euclidean triangle.
     A meaningful sentence is one or the other


   Math and Logic                      Everything else

• analytic: true in virtue of       • synthetic: not analytic. [I]ts
  language alone. [I]t’s validity     validity is determined by the
  depends solely on the               facts of experience.
  definitions of the symbols it
  contains.
                                    • a posteriori (―empirical‖): can
                                      only be known ―after‖ (on the
• a priori: knowable ―prior to‖       basis of) experience
  experience

                                    • contingent: not necessary
• necessary: not logically
  possible that they be false
     The truths of logic and math are analytic

• Objection: If all the assertions which mathematics puts forward can
  be derived from one another by formal logic, mathematicians cannot
  amount to anything more than an immense tautology…[C]an we
  really allow that these theorems which fill so many books serve no
  other purpose than to say in a roundabout fashion A = A?




                                       You betcha!
         Tautologous doesn’t mean obvious

   The power of logic and mathematics to surprise us depends…on the
   limitations of our reason. A being whose intellect was infinitely
   powerful would take no interest in logic and mathematics.

• We reject ―truths of reason‖ which purport to establish facts about
  the world outside of language by a priori reasoning.

• And we reject Kant’s synthetic a priori

   There is a sense in which analytic propositions do give us new
   knowledge. They call attention to linguistic usages, of which we
   might otherwise not be conscious and they reveal unsuspected
   implications in our assertions and beliefs.

• The business of philosophy is analysis: to elicit those features
  linguistic usage and reveal entailment relations.
   A paradigmatic philosophical question

A bear walks a mile south, a mile east and a mile north—and ends
up where he started. How is that possible?

We know the answer of course…

But how come it only works near the North Pole???
  It’s a question about linguistic conventions!




• ―North‖ and ―south‖ trace along longitude lines which converge at the
  North and South poles.

• ―East‖ and ―west‖ trace along latitude lines which are concentric and
  don’t converge;
      “Who cares what games we choose…”

• Whether a geometry can be applied to the actual physical world or
  not, is an empirical question which falls outside the scope of the
  geometry itself. There is no sense, therefore, in asking which of the
  various geometries known to us are false and which are true. In so
  far as they are all free from contradictions, they are all true…[T]he
  propositions of pure geometry are analytic…the reason why they
  cannot be confuted in experience is that they do not make any
  assertion about the empirical world. They simply record our
  determination to use words in a certain fashion.
                           Summing up
• All factually significant propositions are a posteriori (empirical)

    – Sentences which purport to be factually significant but fail the
      Verification Principle are nonsense.

• A priori propositions are devoid of factual content.

    – They’re meaningful only if they’re ―tautologies,‖ i.e. analytic.

• A priori propositions that aren’t tautologies are metaphysical junk—a
  result of our misunderstanding of language

    – ―Substance‖ comes from our ―primitive superstition‖ that subject-
      predicate form reflects the structure of reality.

    – ―Being‖ comes from the surface grammatical quirk that we
      express existential sentences with ―is‖ which also does the job of
      predication. Existence is not a predicate!
                      Some questions…

• What is the status of the Verification Principle itself?

    – Is it an empirical claim made probable by experience?

    – Is it a ―tautology‖ true just in virtue of the meanings of words?

• Do analytic, a priori, necessary and synthetic, empirical, contingent
  line up neatly in the way suggested?

    – analytic and synthetic are semantic notions

    – a priori and a posteriori concern the way in which propositions
      are known

    – necessary and contingent are metaphysical notions concerning
      the conditions with which propositions are compatible
                        More questions

• Suppose the Verification Principle is a methodological prescription:
  has Ayer fiddled it to let in what he likes but exclude what he doesn’t
  like, i.e. metaphysics and theology?

• Does Ayer have an adequate account of mathematics given Gödel’s
  proof that in any system rich enough to formalize arithmetic there
  are propositions which are true within the system that aren’t
  derivable within the system?

• Can the distinction between analytic and synthetic propositions be
  made in a non-question-begging way?



                                            No!