Popper: Falsificationism

1
Popper Falsificationism

• From falsifiability as the criterion that
  distinguishes science from pseudo-science to
  falsificationism as a model of scientific
  method/reasoning.
• A rejection of all forms of inductivism (both
  narrow or naïve, and Hempels sophisticated
  version of inductivism).
• There is no principle of induction that will
  justify induction or an inductivist account of
  scientific method/reasoning
• Like Hempel, Popper emphasizes that there is no
  logic of discovery, but only a logic of
  justification (testing)
• But, unlike Hempel, Popper argues that the logic
  involved in the context of justification or
  testing is deductive and specifically the logic
  of falsification.

2
Poppers explication and defense of falsification

• The rejection of psychologism
• The question of how an idea (hypothesis) occurs
  to a person may be of interest to psychologists,
  but not to those interested in the logical
  analysis of scientific reasoning (i.e., in the
  epistemology of science).
• The former is concerned with matters of fact the
  latter concerned with questions of justification
  or validity i.e., is normative rather than
  descriptive
• Discovery/justification However a scientist
  arrives at a hypothesis, all that philosophy of
  science (epistemology) is concerned with is
  whether the hypothesis is justified.

3
Poppers Falsificationism

• The tests any proposed hypothesis is (or should
  be?) subjected to
• Internal consistency does it include any logical
  contradictions/inconsistencies?
• Is it actually scientific, i.e., falsifiable?
• External consistency is it consistent with
  relevant theories that are currently accepted?
• How does it fare when it is tested?
• So long as a theory avoids being falsified, we
  say it is corroborated (weaker than confirmed).
• There is no inductive reasoning involved here!

4
Poppers Falsificationism

• Stages in scientific reasoning (as it is or as it
  should be?)
• Bold conjectures they go out on a limb, prohibit
  the occurrence of some set of phenomena (events,
  objects, and so forth).
• Rigorous efforts to falsify the hypothesis by
  subjecting it to tests.
• Falsification (or corroboration). If the first,
  rejection of the hypotheses and search for and
• The emergence of a new bold conjecture proceed
  to steps 2, 3 and 4

5
Poppers Falsificationism

• Questions
• If we reject psychologism (the study of how
  scientists actually think and reason), is
  Falsificationism itself an empirical account of
  how they do or an account of how, ideally, they
  should reason?
• If the former, is it in fact how scientists
  proceed do they rigorously attempt to falsify
  the hypotheses they propose?
• If it isnt how scientists actually proceed, what
  is the justification for the claim that they
  should proceed this way?

6
Poppers Falsificationism

• Lets start with the empirical question
• Of the scientists weve read, read about, or seen
  in films, do they seem hell bent to disprove
  their own hypotheses and theories? Granted they
  test them (when they can) but is this to falsify
  them and move on to better hypotheses or
  theories?
• And what of the historical cases weve
  considered? If Falsificationism is supposed to be
  how scientists reason, do these cases support the
  account?

7
Poppers Falsificationism

• The scientific reaction to
• The case of planetary misbehavior and its
  challenge to Newtonian theory
• The scientific reaction to apparent falsifiers of
  the Copernican hypothesis (stellar parallax which
  it predicted is not observed)
• Two more examples
• Darwin took the bright colors, larger size,
  antlers, and other ornaments of many males in a
  species as potentially falsifying his theory of
  natural selection.
• He viewed them as inhibiting survival, rather
  than enhancing it or being benign in terms of
  it.

8
Poppers Falsificationism

• Darwin took the bright colors, larger size,
  antlers, and ornaments of many males in a
  species as potentially falsifying his theory of
  natural selection.
• Why? They not only seemed not to enhance
  survival, but to act directly against it.
• Did he abandon natural selection?
• No, he proposed the hypothesis of sexual
  selection as a secondary evolutionary force that
  enhances reproductive success
• Male-male competition for (relatively scarce)
  females
• Female choice of mates who had such ornamentation

9
Poppers Falsificationism

• The co-discover of natural selection, Wallace,
  was horrified by Darwins new hypothesis,
  maintaining it was
• Ad hoc (Added simply to save the theory)
• Violated the norm that a genuine theory of
  evolution would have one and only one explanation
  or mechanism
• A good Victorian, he found the notion of female
  choice and its having long term consequences at
  least unappealing if not ludicrous.

10
Poppers Falsificationism

• As Darwin noted in his chapter Difficulties on
  theory towards the conclusion of The Origin,
  there were many
• A lack of fossil evidence for the innumerable
  transitional forms his understanding of natural
  selection entailed
• A lack of a theory of inheritance (how parents
  tend to pass on traits to their offspring)
• How can one and same process, natural selection,
  produce trifling organs (a giraffes tail which
  is but a fly swatter) and astounding and seeming
  perfect organs (the eye)?

11
Poppers Falsificationism

• These problems (and they are just a few of those
  that Darwin identified) were not taken as
  falsifying the theory (or even rendering it
  unscientific) by Darwin or many of his scientific
  contemporaries
• They were seen, instead, as among those research
  problems that the emerging discipline of
  evolutionary theory would tackle, while assuming
  that the overall theory of natural selection is
  correct.

12
Poppers Falsificationism

• One problem facing the Aristotelian and Ptolemaic
  model of astronomy (geocentrism) was its
  complicatedness (or what todays physicists might
  describe as its inelegance).
• Because it assumed that planets move in a
  uniform, circular motion and at a uniform speed,
  it had to contend with (among other observations)
  the apparent retrograde motion of some planets.
  Mars, for example, seems at times of the year to
  stop and go in reverse for awhile before resuming
  its regular circular motion

13
Poppers Falsificationism

• To address the problem, astronomers added
  epicycles to planetary orbits
• Smaller (but still circular!) orbits compatible
  with apparent retrograde motion
• As the story goes, the Copernican hypothesis was
  much simpler and superior.

14
Poppers Falsificationism

• But the Copernican model also had to include
  epicycles to make it compatible with apparent
  retrograde motion of planets albeit, somewhat
  less.
• It was not until Kepler recognized that the
  planets orbits are elliptical that astronomers
  no longer needed epicycles.

15
Poppers Falsificationism

• The moral if the need for epicycles was taken to
  be a reason to reject the geocentric model, it
  was not solved (initially) by the Copernican
  model but scientists accepted the latter anyway.

16
Poppers Falsificationism

• So, at least some historical episodes (and actual
  current scientific practices) challenge the
  notion that Falsificationism is the form of
  reasoning and the purpose of testing in which
  scientists engage.
• So what kind of model is it? And what justifies
  it?
• Is it an attempt at rational reconstruction of
  actual scientific practices?
• Is it a normative claim that, however scientists
  actually behave, they should embrace
  Falsificationism as their method?

17
Poppers Falsificationism

• Efforts in the philosophy of science to
  rationally reconstruct actual scientific
  practice are typically designed to show that some
  apparent commitment (for example, to
  non-observables or to saving a theory from
  refutation) can be reconstructed by philosophers
  to show how such commitments arent necessary to
  the science in question or its success.
• This means imposing philosophical normative
  notions (what is rational) on scientific practice
  to, in effect, retell the episode so as to
  preserve a favored view of what is rational.

18
Poppers Falsificationism

• Is Popper engaged in this?
• Or is he laying out a model of how scientists
  should behave in practice?
• If the latter, does the model have what it needs
  to explain the developments, trajectories, and at
  least apparent successes of various sciences in
  various historical periods?
• Would it have been more rational or scientific to
  reject the Copernican hypothesis? Or Darwins
  natural selection?

19
Poppers Falsificationism

• On the other side, Poppers model seems to many
  bench scientists reflective of
• Their commitment to fallibilism
• Their rejection of dogmatism
• Their willingness, when and as appropriate, to
  abandon a long-standing theory when the evidence
  mounts up against it.
• As an example, many who have testified or written
  against Creation Science and/or ID, cite
  falsifiability as something the latter lack, and
  the 3 commitments above as what distinguishes
  science from CS and ID

20
Poppers Falsificationism

• One possibility Poppers model is both empirical
  (in keeping with actual scientific practice) and
  normative (a prescription of how scientists ought
  to behave
• Popper takes scientific revolutions as the
  norm, providing the most important empirical
  examples from which the most important normative
  conclusions can be drawn (but he may be wrong)
• But what if revolutions in science are rare and
  thus do yield the best understandings of most of
  (the bulk of) actual scientific practice?

21
Poppers Falsificationism

• To return, briefly, to the issue of Ad hoc
  hypotheses (which, by the way, scientists often
  charge creationists with appealing to in order to
  save their theory in light of numerous
  counterexamples).
• We used the case of planetary misbehavior to
  raise the issue of whether it is always
  unwarranted (non-scientific) to supplement a
  theory with an additional hypothesis to explain
  an apparent counterexample, and whether it is
  possible to know if a hypothesis is ad hoc at the
  time it is proposed, or only in hindsight.

22
Poppers Falsificationism

• But arent there instances where we might think a
  hypothesis is ad hoc even before its tested.
• A different (in this case, imaginary) episode
  involving planetary misbehavior
• Suppose that no new planet p is discovered that
  explains the orbit of p in a way consistent with
  Newtons theories
• And our scientist proposes that the previously
  undiscovered planet is too small for todays
  telescopes to be able to see
• So she applies for a grant to build a stronger
  telescope and in three years time it is ready
• The telescope is trained to that part of the sky
  where p should be but it doesnt seem to be.

23
Poppers Falsificationism

• Does our scientist give up on the existence of
  this not yet discovered planet?
• No, she proposes that a cloud of magnetic dust
  hides the planet from us. She calculates the
  location and properties of this cloud, and
  applies for a research grant to send a satellite
  up to check to see if she is right about the
  cloud.
• Were the satellites instruments (perhaps brand
  new just for this mission) to detect the cloud,
  this would be hailed as a victory
• But if not...? When does one give up?

24
Poppers Falsificationism

• Is the determination of falsification relative
  to the level of previous success a theory enjoyed
  and/or the scientific communitys judgment?
• Is the logic of falsification aptly a description
  of reasoning in a scientific revolution, but not
  when science is not ready for/expecting a
  revolution?
• Modus Tollens is a deductively valid argument
  form, but what does the role of auxiliary
  assumptions, plus the inference If H, then (if
  C, then E), suggest about all that it presupposes
  and, thus, its limits?