Ayer, The Elimination of Metaphysics

1
Ayer, The Elimination of Metaphysics

• September 15, 2008

2
Chapter 1 - Introduction

• Ayer subscribes to a Verification Principle.
• Motivation for Verification Principle Science.
• This gives us a method to test if the
  Verification Principle is correctly formulated.

3

• Strong Verifiability
• A sentence is verifiable in the strong sense iff
  it is conclusively established by experience.
• experience could rule out the possibility that
  the sentence is false.
•  

4
Problems with Strong Verifiability
UNIVERSAL STATEMENTS All water boils at 100 C
(at regular atmospheric pressure). All humans
descended from common ancestors. The metric
tensor field is defined on all points of
spacetime. F ma
Q Why are universal statements not conclusively
established by experience?
5
Problems with Strong Verifiability
STATEMENTS ABOUT THE REMOTE PAST Dinosaurs
roamed the earth 65 million years ago. Caesar
crossed the Rubicon in 49 BC.
Q Why are statements about the remote past not
conclusively established by experience?
6
Strong Verifiability A sentence is verifiable
in the strong sense iff it is conclusively
established by experience.
Strong Falsifiability A sentence is
falsifiable in the strong sense iff it is
conclusively refuted by experience.
experience could rule out the possibility that
the sentence is true.
7
Problems with Strong Falsifiability
HOLISM Hypothesis All salts dissolve in
water. 1. Takes some salt NH4Cl 2. Take some
water H2O 3. Try to dissolve the salt in the
water. 4. It doesnt dissolve.
Q Is the hypothesis conclusively refuted?
8
Problems with Strong Falsifiability
EXISTENTIAL STATEMENTS There is at least one
naturally occurring instance of an element with
atomic number 102. There is life on
Mars. There is a planet in the universe the same
size as the earth.
Q Why are existential statements not
conclusively falisfiable?
9
Strong Verifiability A sentence is verifiable
in the strong sense iff it is conclusively
established by experience.
Strong Falsifiability A sentence is
falsifiable in the strong sense iff it is
conclusively refuted by experience.
Weak Verifiability A sentence is verifiable
in the weak sense iff any observations are
relevant to its truth or falsehood.
10
General Idea Its NOT that for a statement to be
meaningful it must be possible for it to be
conclusively established by observations. RATHER,
to be meaningful it must be possible that
observations support the statement or are
relevant to the statement or render it plausible.
Ayers Specific Proposal A sentence, S, is
meaningful iff at least one observation sentence,
O, can be deduced from S in conjunction with
other premises, P1, P2, , Pn, without O being
deducible from the other premises (P1, P2, , Pn)
alone.
11
Problems with Weak Verifiability
EVERYTHING IS VERIFIABLE S The Absolute is
pure potentiality. P If S, then it is sunny
outside. Note It is sunny outside, is an
observation sentence.
Church, Alonzo. Review of Language, Truth, and
Logic Second Edition, Journal of Symbolic
Logic, 14 (1949) 52-53.
12

• The Moral for Philosophy of Science
• Statements in science are not (usually)
  deductively proven by observation statements.
• We need to understand inductive inference if we
  are to understand the logic of science.
• Ayers Weak Verifiability Principle can be seen
  as a (failed) attempt at this.

13
How Did Philosophy Go Wrong (according to Ayer)?
SC Santa Claus does not exist.
14
How Did Philosophy Go Wrong (according to Ayer)?
Russells Analysis The president of the U.S. is
from Texas 1. At least on person is
president of the U.S., and 2. At most one person
is president of the U.S., and 3. That person is
from Texas.
15
How Did Philosophy Go Wrong (according to Ayer)?
Russells Analysis Santa Claus does not exist
Santa Claus is nonexistent 1. At least on
person Santa-Clauses, and 2. At most one person
Santa-Clauses, and 3. That person is nonexistent.
16
How Did Philosophy Go Wrong (according to Ayer)?
Russells Analysis Santa Claus does not exist
Santa Claus is nonexistent 1. At least on
person Santa-Clauses, and 2. At most one person
Santa-Clauses, and 3. That person is nonexistent.
17
How Did Philosophy Go Wrong (according to Ayer)?
Russells Analysis Santa Claus does not exist
NOT Santa Claus exists NOT 1. At least on
person Santa-Clauses, and 2. At most one person
Santa-Clauses, and 3. That person exists.