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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 representative, or causal, realism: Berkeley (review), Kant

Response to metaphysics: science as antidote

Logical positivism:

1)empiricist criterion of meaning;

2)role of philosophy: epistemology of science and conceptual analyses

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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 mind-independent (= 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 mind-independent 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 non-tautological 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 self-evidently 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?