Updated: 03 March 2000

The Realist Picture

Start with observations

Seek explanations

Produce theories

Explain by reference to the unobserved

Inference to the best explanation

Galileo - mountains on the moon

Einstein - atoms via Brownian motion

Thomson - electrons via scintillations

Confirm by successful novel predictions

1.

The theory provides a literally true (or truth-like) account of the underlying mechanisms in the world

Real realism –

truth as correspondence

or

reject reconstruals of truth (eg Peirce)

Explanatory Realism

Verisimilitude

Aim of science is the truth-related aim of having theories of ever greater verisimilitude.

Problems: meaning of approximate truth

evidence for it

2.

Observational success of science

Science uses IBE

Use IBE in your theory of science

What is it about today’s theories that enables them to give better predictions?

theories are more approximately true

advanced in contexts of Kuhnian scepticism

3.

Instrumentalism

Historical sources

Limited epistemic skepticism

How do you know about electrons ?

Experience is the source of all knowledge, don’t have experience of electrons.

Limited - knowledge of observable states

4.

Limited semantic skepticism

What do you mean?

Cannot give verbal definitions or ostensive examples for theoretical terms.

No more meaning than Hodge’s uninterpreted symbols

5.

Instrumentalism

theories are just predictive tools

1. Semantic

T-terms lack meaning

T-sentences lack truth-values

2. Epistemological

T-terms have meaning and T sentences have truth-values. But utterly unknowable.

6.

Constructive Empiricism

van Fraassen: The Scientific Image

aim of science: empirical adequacy

scientist does not believe a theory

scientist “accepts” a theory

= believing in its predictive success

7.

Objections to Explanatory Realism

Nothing to explain.

Theories picked for predictive power. That is why they are predictively successful.

IBE

- question begging - instrumentalist challenges its use as an epistemic tool in science

- explanation not linked to truth

8.

no satisfactory account of verisimilitude (Laudan : Science and Values)

historical record is dubious (Laudan)

Underdetermination of theory by data.

9.

Constructive Empiricism

1. semantic realism

2. Not traditional scepticism

IBE ok from observables to observables

Crucial to distinquish between:

O and T

O and non-O

i) Schlick : O

absolute certainty

inner experience - sense data

ii) Carnap - matter of degree

quickly, accurately, confidently decide

iii) van Fraassen - biological basis - what humans could (if suitably located) settle by using unaided senses

10.

Local realism

aim of science goes beyond that of empirical adequacy

Inference to the Best Explanation

global use

Argues for TV on the grounds that it provides best explanation of increasing observational successes of science

local uses

Seeks to justify positing atoms, electrons etc

Miller “book length argument for realism”

11.

Underdetermination of theory by data

Copernicus

Ptolemy

see hand-out

Underdetermination by the actual available data

Threat to IBE ?

Agnostic realism

- wait and see

12.

Undetermination of theory by all actual and possible data

For any theory T1 there is a theory T2 :

T1 and T2 are incompatible.

T1 and T2 are empirically equivalent

T1 and T2 are fare equally well on all other epistemic principles of theory choice.

13.

Strong UTD - applies to all theories

Weak - applies to some theories

Observationally omniscient God

What hope for realism?

Inter-Galactic Conference

Newton ... Einstein

Notwen... Nietsnie

14.