Transcript From metaphysics to logical positivism

From metaphysics to
logical positivism
The metaphysician tells us that empirical truth-conditions
[for metaphysical terms] cannot be specified; if he asserts
that nonetheless he ‘means’ something, we show that this is
merely an allusion to associated words and feelings, which
however, do not bestow a meaning
Rudolf Carnap (150)
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Metaphysics to Logical Positivism
 Responses to
 Logical positivism:
representative, or 1) empiricist criterion
causal, realism:
of meaning;
Berkeley (review), 2) role of philosophy:
Kant
epistemology of
 Response to
science and
metaphysics:
conceptual
science as
analyses
antidote
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Idea-ism to Idealism: Berkeley
 Recall Berkeley’s argument for Idealism:
1. We perceive such things as trees and stones
2. We perceive only ‘ideas’ and their aggregates
(Idea-ism)
3. Ideas and their aggregates cannot exist
unperceived
4. Therefore, trees and stones are ideas and
their aggregates, and cannot exist
unperceived (Idealism)
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Berkeley’s Idealism
 For Berkeley, all properties are
secondary; that is there are no mindindependent (= primary) properties
 Idealism is a “metaphysical thesis that
all that exist is mental … in nature,
hence it is incompatible with any form of
metaphysical realism” (144).
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Kantian alternative
 Kant agrees with metaphysical realism:
there is a mind-independent world
 However, we don’t know anything about it
(noumenal world)
 “Our knowledge is of the world as it is for
us” the phenomenal world (141)
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Metaphysics to Logical Positivism
 If you were a scientifically-minded philosopher,
what to make of the arguments by Berkeley and
Kant?
 Of course we should believe in a mindindependent world and we can know that world.
 How do we argue for that conclusion?
 That such a world exists is the inference to the
best possible explanation of all the evidence we
have
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Positivism
 Logical positivism has its roots in Auguste
Comte’s (1798-1857) ‘positivist’
philosophy
 The ‘positivist’ movement is a backlash
against the dominance of metaphysics in
19th Century philosophy
 Think about Hegel’s concept of ‘Spirit’ or
‘Absolute knowing’
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Positivism
 Comte claims that societies pass through
three stages:
a) Theological: appeal to deities to explain the
nature of things in themselves
b) Metaphysical: appeal to unknown forces to
explain the nature of things in themselves
c) Scientific: renounces pretense to know the
nature of things in themselves; science
should stick to predictions.
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Positivism
 Comte’s positivism emphasizes:
a) Empiricism
b) Renounce the pretension to know the
nature of things in themselves
1) anti-theoretical entities
2) anti-metaphysics (in general)
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Logical Positivism
 Logical positivism emerged in the 1920s.
 For logical positivists, the antidote to
metaphysical talk: logic, mathematics and
science
 Mathematical logic provides the framework
in which theories can be precisely
formulated
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Logical Positivism
 For logical positivists, “if the connections between
ideas and associated experience could be made
precise then it would be possible to separate
meaningless metaphysical [talk] from empirical
science” (Ladyman 149)
 Assumption: words get their meanings by
connection to experience
 Implication: “no matter of fact can be intelligibly
thought about can go beyond all possible sense
experience” (Ladyman 150)
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Logical Positivism
 Empiricist criterion of meaning: “to be
meaningful a word must have some
connection with what can be experienced”
(ibid).
 Contrast ‘thing-in-itself’ with ‘microwave’
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Logical positivism—empiricist
criterion of meaning
 Empiricist criterion of meaning used to
demarcate between science and
pseudo-science: pseudo-science uses
meaningless concepts.
 By the empiricist criterion of meaning,
claims made in theology are
meaningless.
 By that criterion, claims in ethics mean
something different than what we think.
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Summary of logical positivist
commitments (157)
1. Science is the only intellectually respectable
form of inquiry
2. All truths are either analytic a priori or
synthetic a posteriori
3. Philosophy explains the structure, or logic,
of science. The role of philosophy is the
epistemology of science and conceptual
analyses
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Summary of logical positivist
commitments (157)
1. Logic expresses precisely the relation
between concepts
2. Verifiability criterion of meaning: “a statement
is literally meaningful if and only if it is either
analytically or empirically verifiable”
3. Verification principle: “the meaning of a nontautological statement is its method of
verification; that is the way in which it can
shown to be true”
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Positivist epistemology
 Positivists hold that our knowledge is built
up from basic beliefs which are selfevidently true (i.e. immune from doubt)
 All other beliefs are justified either
deductively or inductively from basic
beliefs
 This view is called FOUNDATIONALISM
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Positivist epistemology
 Basic beliefs are called ‘protocol
statements.’
 Protocol statements: “first person, singular,
present tense, introspective reports” (152).
 Here’s an example: ‘I seem to sense a
patch of red in my visual field.’
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Positivist epistemology
 Why is this claim immune from doubt?
 Even if I am wrong about the object I
see, I can’t doubt that it appears that I
am sensing a patch of red in my visual
field
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Logical positivist epistemology
 ‘I seem to sense a patch of red in my
visual field.’
a) Is strongly verified because it simply
reports one’s sense experience
b) Weakly verifies other non-basic
statements, or empirical hypotheses, ‘I
see a red ball in the corner’.
 Why do protocol statements only weakly
justifies these other statements?
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Dilemma for logical positivism
1. We (claim to) know lots about the world
2. We only know protocol statements and
analytic truth
 To avoid skepticism about the external
world, logical positivists need to infer (1)
from (2).
 What kind of argument can they use?
Deductive? Inductive?
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Solution to dilemma
 Solution: “Proposition asserting the
existence of physical objects are
equivalent to ones asserting that the
observer will have certain sequence of
sensations in certain circumstances”
(Ladyman 153).
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Logical positivism: phenomenalism
 Talk of perceived or possible objects is
reducible to talk of actual or possible
experience.
 Physical objects are “permanent possibility of
sensation”; they are “logical constructions out
of actual and possible sense experience”
(ibid).
 This position is called PHENOMENALISM
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Logical positivism
 With logical positivism, physical objects are
“permanent possibility of sensation”; they
are “logical constructions out of actual and
possible experience”
 This move, though seemingly counter
intuitive, has the virtue of doing away with
metaphysical debates. Why?
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Logical positivism
 For the logical positivists, the table of
commonsense, is a mere construction from
sense-data.
 What about the ‘scientific’ table, the table of
atoms, electrons, etc?
 Is the ‘scientific’ table also a mere
construction from sense-data?
 Do we have such sense-data?
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