PY226 Philosophy of Science

1
PY226Philosophy of Science

• Alice and so the scientific method consists in
  unbiased accumulation of observations and
  inductive inference from them to generalisations
  about phenomena (Ladyman p. 30)

2
Key terms

• Scientific revolution
• Instrumentalism
• Realism
• Deduction
• Inductive inference
• Inductivism

3
Scientific Method a bit of history

• The scientific revolution the way scientific
  inquiries were carried out underwent a radical
  shift during the 16th and 17th centuries from the
  influence of Aristotelian philosophy (384-322
  BCE).
• New theoretical approaches to mechanics, the
  motion of matter, and new developments in
  mathematics.
• Key figures Galileo (1564-1692) and Newton
  (1692-1727)

4
Scientific Revolution earlier episode

• Copernicus (1473-1543) an earlier failed
  attempt to revolutionize astronomy
• Heliocentric (Sun at the centre) vs. Geocentric
  (Earth at the centre) system
• Geocentric system based on Aristotelian thinking
• a) Earth and Heavens have different natures
• b) Motion on earth different from the heavens

5
Geocentric view

• Problem with geocentric view apparent retrograde
  motion of planets
• Ptolemaic solution epicycles
• What happens when there are more anomalies?
• More epicycles

6
Copernican revolution heliocentric view

• Copernicus proposed a simple solution kept
  circular motion of planets but placed the sun at
  the centre of the universe
• Kepler (1571-1630) modification of Copernicus
  view elliptical orbits
• Osianders failed ruse
• Motion of the earth a mathematical fiction rather
  than asserting that the earth was orbiting the sun

7
Instrumentalism

• Instrumentalism scientific theories need not be
  believed to be true, but rather should be thought
  of as useful or convenient fictions (p. 17).
• Contrast with realism
• scientific theories should be taken literally

8
Deduction vs. Induction

• Bacon (1561-1626) proposed a new tool (Nouvum
  Organum) for scientific inquiry induction
• Deduction (syllogistic reasoning)
• All Xs are Ys
• A is an X
• Therefore, A is a Y

9
Deduction

• Validity If the premises are true, the
  conclusion cannot be false.
• Arguments with the above formal characteristic
  are VALID arguments
• Arguments are SOUND if a) they are valid, and b)
  the premises ARE true

10
Deduction

• Valid deductive arguments are truth preserving
• The paradigm of deductive reasoning in science is
  Euclidean geometry
• A science based on deductive reasoning
  discovers necessary truthsthey cannot be
  otherwise.
• An aside Deductive reasoning Descartes

11
Deduction

• Downside
• A) the conclusion contains no new information
  than what is in the premises.
• B) Valid deductive arguments may not be good
  arguments
• Wong says that he is smart
• Whatever Wong says is true
• Therefore, Wong is smart

12
Deduction

• Invalid arguments if the premises are true but
  the conclusion can be false
• Invalid arguments are logical fallacies
• If Socrates gets run over by a truck, he will be
  dead
• Socrates is dead
• Therefore, Socrates was run over by a truck

13
Deduction

• Not all invalid arguments are bad however
• I see a white swan at T1
• I see a white swan at T2
• I see a white swan at T3
• I see a white swan at Tn
• Therefore, all swans are white
• Notice that there is nothing in the premises
  themselves that tells us that all swans are white.

14
Induction

• Heres another example of a plausible inductive
  inference
• There are no signs of forced entry
• The guard dogs did not bark
• Therefore, the heist was an inside job
• Induction is the technical term given to various
  deductively invalid but allegedly good
  arguments

15
Bacons new tool for science

• Bacons experimental method make observations
  not based on pre-conceived biases and gather a
  lot of information about the state of affairs
  under consideration, and then step by step reach
  general conclusion.
• Experimental because he advocates controlling the
  conditions to see what would happen
• Crucial experiments

16
Bacons method

• Bacons method based on observation and induction
• The simplest form of inductive reasoning is
  enumerative induction (e.g. the white swan
  example)
• Question when would it be legitimate to draw a
  generalisation from instances of observation
  statements?
• When N is sufficiently large

17
Naïve inductivism

• Naïve inductivism when a large number of
  observations of Xs under a a variety of
  conditions have been made, and when all Xs have
  been found to possess property Y, and when no
  instance has been found to contradict the
  universal generalisation all Xs possess property
  Y (Ladyman p. 29)
• Bacons proposal represents the scientific method
  for someone who subscribes to naïve inductivism.

18
Looking forward to next meeting

• Thomas Lets concentrate on your principle of
  induction and the idea about observation without
  prejudice or preconception. How do you know
  that your principle of induction is true, and
  observation without any bias whatsoever is
  impossible (Ladyman, p. 30)
• Should we believe in induction?