Lecture Five Kuhn Revolution

1
Lecture FiveKuhn Revolution Rationality

• Dr Emma Tobin
• Philosophy Bristol

2
Re-cap

• (1) Deductivism (Aristotle)
• (2) Inductivism (Bacon)
• Humes Problem of Induction
• Two Responses
• (1) Sophisticated Inductivism - Logical
  Empiricism (Carnap/Reichenbach)
• (2) Falsificationism (Popper)

3
Sophisticated Inductivism

• All the statements of empirical science must be
  directly verifiable to be meaningful.
• Humes problem of Induction can be avoided once
  we distinguish between the context of Discovery
  Justification.
• Theories can be confirmed in relation to the
  evidence for them, independently of how they were
  produced.
• Carnap Reichenbach (Mathematical Probability).

4
Falsificationism

• The falisifiability of a system (its capability
  of being refuted) is the demarcation criterion.
• A theory that survives a falsification is
  corroborated.
• Increasing Verisimilitude.

5

• Popper and the logical empiricists disagree about
  method, but share common assumptions about the
  rationality of science.

6
Shared Assumptions

• (1) Scientific knowledge is cumulative,
  progressive and has a definite trajectory.
• (2) Science is (or will be) unified.
  (Reductionism)
• (3) There is a demarcation criterion.
• (4) Observation experiment has a crucial role.
• (5) We can evaluate the evidence for a hypothesis
  (a) by the logic of confirmation or (b) by
  assessing whether it is falsifiable.
• (6) The contexts of Discovery Justification
  should be distinguished. The latter is more
  important.
• (7) Scientific terms are meaningful.
• (8) Science is rational.

7
Thomas Kuhn (1922 -1996)
Kuhn rejects the idea that science progresses by
the linear accumulation of new knowledge.
8

• No Theory Neutral Observation
• No Single logic of Testing.
• Scientists Values and Commitments influence
  scientific results.
• Science is not cumulative, sometimes theories are
  abandoned.

9
2 Phases of Science

• (1) Normal Science (Work within an established
  paradigm)
• (2) Scientific Revolutions (Paradigm Shifts)

10
Paradigms

• Disciplinary Matrix (The current agreed answers
  to fundamental questions/preferred methodologies
  that are assumed by scientists in their everyday
  work)
• Exemplars (Successful examples from science that
  scientists learn and seek to replicate in solving
  new scientific problems.)

11
Examples of Paradigms

• Geocentrism heliocentrism
• The Caloric Theory of heat vs. the Kinetic
  Theory of Heat
• Phlogiston Theory of Combustion the Oxidisation
  Theory of Combustion.

12
Normal Science

• Normal Science commitment to a background
  paradigm.
• Puzzle-Solving Mopping Up
• (1) Fact-gathering (e.g. Stellar position
  (Astronomy) or boiling points and acidity tests
  of solutions (Chemistry).
• (2) Designing a new experiment/apparatus (e.g.
  Atwood's machine to give a demonstration of
  Newtons 2nd law within the Newtonian
  paradigm).
• (3) Articulating constants (Avogadro's number)
  and quantitative laws (Boyles law relating gas
  pressure to volume) .
• (4) Resolving Residual Ambiguities

13

• Scientists rarely question the paradigm.
• Only those scientific problems that test the
  paradigm from within are considered worthwhile.
• Scientific Conservatism -- cherished beliefs from
  within the paradigm.
• Normal science within paradigms is a cumulative
  process.

14
Scientific Revolution

• Scientific Revolutions (Paradigm Shifts) are
  very rare. (vs. Popper science is in a constant
  state of revolution.)
• Scientific Revolutions emerge out of a growing
  disquiet among a group of scientists that the
  anomalies facing the paradigm have reached a
  crisis point.

15
The Copernican Revolution Paradigm Shifts

• The shift from the Ptolemaic to the Copernican
  worldview is a paradigm shift.
• The transition between competing paradigms
  cannot be made a step at a time, forced by logic
  and neutral experience. Like the Gestalt shift,
  it must occur all at once (though not necessarily
  in an instant) or not at all. Kuhn The Structure
  of Scientific Revolutions 150.

16
(No Transcript)
17

• Kuhns Example The Copernican Revolution
• Change from Ptolemys geocentrism to Copernican
  heliocentrism.

18
(No Transcript)
19
Retrograde Motion an Anomaly

• Each night, every planet moves from West to East
  across the sky.
• Occasionally, however, a planet's motion will
  reverse direction, and the planet will move from
  East to West against the background
  constellations for a time and then continue from
  West to East again.
• Ptolemy refined Aristotle to accommodate the
  anomaly.

20
Ptolemys Geocentrism
In Ptolemy's system the Earth sits
somewhere off the true center of each planets
circular orbit (deferent). Ptolemy attempted to
make the observations of the changing positions
of the stars ands planets consistent with a
geocentric worldview.
21
(No Transcript)
22
The Copernican Paradigm

• Copernican Heliocentrism is a new paradigm which
  requires a paradigm shift.
• The Anomaly of retrograde motion is explained by
  the fact that planets further away from the sun
  move more slowly that those close to it. E.g. The
  observed retrograde motion of Mars occurs because
  the Earth passes by at a faster rate.

23
Phlogiston Theory Oxygen

• Phlogiston Paradigm of Combustion Phlogiston
  was a substance that was released from materials
  when they burned.
• It was observed that most things lose weight when
  burned.
• Anomalies Some metals increase their weight
  when burned.
• As more and more cases were observed the
  Phlogiston theory reached crisis point.
• Scientists were poised for a new paradigm.

24

• Lavoisier (1777) proposed that phlogiston does
  not exist and is not released from materials when
  burned.
• He proposed that we replace it with the theory
  that oxygen is gained by materials when burned.
• The oxidisation theory results in the acceptance
  by the scientific community of a new paradigm.

25
Incommensurability (lack of common measure)

• Theories across paradigms are not translatable
  (meaning incommensurability).
• The term space in Newtonian theory has an
  entirely different meaning to space in
  Einsteins relativity theory.
• What counts as evidence is always subject to
  our commitment to a background paradigm.

26
Objectivity?

• How can we rationally compare two competing
  paradigms if they are incommensurable?
• There is no relevant objective standard for
  comparing them. Assent of the scientific
  community to paradigm change is enough.
• Science progresses through universal assent of
  the scientific community.

27
Scientific Progress?

• How does science differ from Art, politics,
  sociology and even pseudo-sciences like
  Astrology?
• Traditional answer science progresses.
• Kuhns answer
• Scientific progress is not different in kind
  from progress in other fields, but the absence at
  most times of competing schools that question
  each others aims and standards makes the progress
  of a normal-scientific community far easier to
  see.
• Kuhn The Structure of Scientific Revolutions
  163

28
Paradigm Choice

• The new paradigm resolves some outstanding and
  generally recognized problem that can be met in
  no other way.
• (2) The new paradigm preserves a relatively large
  part of the concrete problem-solving ability that
  has accrued to science through its predecessors.

29
Criterion of Demarcation

• Yet despite these losses to the individual
  communities, the nature of such communities
  provide a virtual guarantee that both the list of
  problems solved by science and the precision of
  individual problem-solutions will grow and grow.
  . What better criterion than the decision of
  the scientific group could there be?
• Kuhn The Structure of Scientific Revolutions
  170

30
Recall Shared Assumptions

• Scientific knowledge is cumulative, progressive
  and has a definite trajectory.
• (2) Science is (or will be) unified.
  (Reductionism)
• (3) There is a demarcation criterion.
• (4) Observation experiment has a crucial role.
• (5) We can evaluate the evidence for a hypothesis
  by (a) a logic
• of confirmation or (b) by assessing whether it
  is falsifiable.
• (6) The contexts of Discovery Justification
  should be
• distinguished. The latter is more important.
• (7) Scientific terms are meaningful.
• (8) Science is rational.

31
The Kuhnian account of Science

• (1) Scientific knowledge is not cumulative, does
  not follow a linear trajectory.
• (2) Science may never be unified because theories
  are incommensurable.
• (3) There is no objective demarcation criterion.
  It is the decision of the scientific community.
• (4) Observation experiment is always
  theory-laden and subject to a paradigm. It should
  not be taken too seriously.
• (5) Evidence for a hypothesis is subject to our
  background paradigm.
• (6) The contexts of Discovery Justification are
  both relevant to the epistemology of science.
• (7) Scientific terms are meaningful only within
  paradigms and not across paradigms..
• (8) Science is irrational.

32
Feyerabend (1924-1994)
Scientific Anarchism There is no
universal Scientific method.