Realism

1
Realism Anti-Realism

• Dr Emma Tobin
• Philosophy
• Bristol

2

• Should we believe in what science tells us
  exists?
• Do quarks/viruses/DNA (e.g. unobservable
  entities) exist?
• Scientific Realism - Yes
• Instrumentalism - Yes, but only to a degree.
• Scientific Anti-Realism - No

3
The Views
4
Scientific Realism

• (1) The observable and unobservable entities
  described by the theory exist objectively and
  mind-independently. (Metaphysical)
• (2) It is ra8itional to believe what scientific
  theories say about observable and unobservables
  entities. Our current scientific theories are
  approximately true. (Epistemological)
• (3)A theory is true in positing entities, if the
  entities talked about by the theory exist and the
  theory corresponds to facts about the world.
  (e.g. a Correspondence Theory of Truth)
  (Semantic)

5

• (1) Electrons exist (metaphysical thesis)
• (2) We should believe that the entities
  (electrons) posited by electron theory exist.
  (epistemological thesis). Electron theory is
  approximately true.
• (3) Statements about electrons are true/false
  because they correspond to electrons in the
  world. (semantic thesis)

6
The No Miracles Argument

• The modern positivist has to leave it without
  explanation (the realist charges) that electron
  calculi and space-time calculi and DNA
  calculi correctly predict observable phenomena
  if, in reality, there are no electrons, no curved
  space-time and no DNA molecules. If those
  objects dont exist at all, then it is a miracle
  that a theory which speaks of curved-space time
  successfully predicts phenomena. (Putnam (1978)
  18)

7
Inference to the Best Explanation

• We ought rationally to infer that the best
  explanation of what we observe is true.
• (e.g.) if Electron Theory is the best explanation
  of what we observe, then we should infer that
  electron theory is true.

8
Scientific Anti-Realism

• Anti-realists only have to deny one of the
  commitments of scientific realism.
• Deny (1) that the entities exist or that they
  exist mind-independently.
• Deny (2) that we can know that our current
  scientific theories are approximately true.
• Deny (3) that there is a correspondence between
  the statements in our theories and facts about
  the world.

9
Scientific Anti-Realism

• The Anti-Realist needs an argument
• (1) The Pessimistic Meta-Induction
• (2) Underdetermination
• (3) The Quine - Duhem Thesis

10
(1) The Pessimistic Meta-Induction

• Meta-Induction about scientific theories.
• Entities and theories that once were thought to
  be true turned out to be false in the history
  of science.
• (e.g. phlogiston theory/electromagnetic ether)
• Conclusion All our present theories will turn
  out to be false.
• No good reason for thinking our present theories
  are true (or approximately true.)

11
(2) The Underdetermination Argument

• Some current Theory T is known and all the
  evidence is consistent with T
• There is an alternative Theory T which is also
  consistent with the evidence. (Empirically
  equivalent)
• If all the evidence for T is also consistent with
  T, then there is no reason to believe T to be
  true rather than T.

12
(No Transcript)
13
Ptolemys Geocentrism
Ptolemy amends the geocentric picture to
include epicycles so as to account for observed
Retrograde motion.
14
(No Transcript)
15

• Ptolemys geocentrism and Copernican
  Heliocentrism were for a while empirically
  equivalent.
• Both consistent with the observed evidence.
• Both views entailed the planets and the moon
  would
• appear in the same region of the sky.
• Both could account for retrograde motion.
• Nothing observed could lead us to accept one
  theory as more true than the other.
• The evidence underdetermines the theory.
• Yet taken literally these theories entail
  entirely inconsistent worldviews.

16
Weak Strong Underdetermination

• Weak Underdetermination - because observations
  and experimental data are consistent with more
  than one theory we should suspend judgement about
  which theory is true.
• Strong Underdetermination - For any theory, there
  will always be another theory that is consistent
  with the evidence. Theory choice is radically
  underdetermined.

17
Reply Observable vs. Unobservable

• The empirical equivalence of theories requires
  that the observations of a theory are clearly
  distinguished.
• But, there is no clear-cut distinction between
  observables and unobservables.
• And, the observable/unobservable distinction
  might change over time with our theories. Laudan
  Leplin (1991)
• Therefore, empirically equivalent theories may be
  distinguished in the future (e.g. new
  instruments).
• There is no reason to believe that there will
  always exist strongly empirically equivalent
  theories.

18

• All theories are underdetermined by empirical
  data (holism).
• The totality of our so-called knowledge or
  beliefs, from the most casual matters of
  geography or history to the profoundest laws of
  atomic physics or even of pure mathematics and
  logic, is a man-made fabric which impinges upon
  experience only along the edges. (Quine Two
  Dogmas of Empiricism 39)

19
Reply Empirical Equivalence vs. Evidential
Equivalence

• When two theories are empirically equivalent,
  there are further factors which may count so that
  they are not evidentially equivalent.
• Simplicity/ Elegance
• Strength
• Explanatory/Predictive Power
• Accuracy

20
(3) The Duhem -Quine Problem - The
Impossibility of Crucial Experiments

• It is impossible to test a scientific hypothesis
  in isolation, because an empirical test of the
  hypothesis requires one or more background
  auxillary hypotheses.(e.g. testing a theory
  involves values for physical constants).
• Any seemingly disconfirming observational
  evidence can always be accommodated to any
  theory, depending on the auxilliary hypotheses.
• The realist can only choose between theories in a
  purely pragmatic fashion.

21
The finitude of Scientific Testing

• Physics vs. Metaphysics.
• Physics the classification of experimental
  results.
• Metaphysics the nature of reality.
• A theory in physics can never be regarded as
  absolutely definitive, because we belief in it
  based only on a finite series of experiments.
• Open empirical possibility that a different
  theory will still explain the same results.

22

• Duhem believed that only in the field of physics
  can a single individual hypothesis not be
  isolated for testing.
• Quine -- All theories are underdetermined by
  empirical data (holism).
• The totality of our so-called knowledge or
  beliefs, from the most casual matters of
  geography or history to the profoundest laws of
  atomic physics or even of pure mathematics and
  logic, is a man-made fabric which impinges upon
  experience only along the edges. (Quine Two
  Dogmas of Empiricism 39)

23

• Although the arguments against realism are
  strong, is extreme scientific anti-realism
  warranted?
• Is there a path between realism and anti-realism?
  
• (1) Instrumentalism
• (2) Constructive Empiricism

24
Phenomena vs. Noumena

• Noumena - Things in Themselves
• Phenomena - Things as we perceive them
  (appearances, or objects of the senses.)

25
Instrumentalism (Laudan)

• A theory with greater explanatory scope than any
  other may be instrumentally useful. This success
  does not, for historical reasons, license belief.
  
• Scientific theories are not literal descriptions
  of reality, but they are useful instruments.
• Nevertheless, science can be said to be
  cumulative, because it uses the theoretical
  instruments of science to solve empirical
  puzzles.
• Laudan (1977) the problem-solving ability of a
  theory is the number and importance of solved
  empirical problems minus the number and
  importance of the anomalies.

26
Constructive Empiricism (Van Fraassen)

• Scientific theories should be taken literally,
  but this does not require belief in the entities
  postulated by the theories.
• An empirically adequate scientific theory saves
  the phenomena. It correctly describes what is
  observable (does not have to be observed).
• Scientific theories can only achieve empirical
  adequacy.

27
The Views