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Title: More%20mental%20gymnastics


1
Lecture 8
  1. More mental gymnastics
  2. Tales from the history of science
  3. Poppers solution to the problem of induction
  4. Which of two possible conclusions about
    scientific reasoning is Popper actually arguing
    for?
  5. Is either argument successful?

2
  • On a distant island, there are 3 kinds of humans
    Knights, Knaves, and Normals.
  • Knights always tell the truth. Knaves always lie.
    Normals sometimes lie and sometimes tell the
    truth.
  • Detectives investigating a crime questioned 3
    inhabitants, A, B, and C of the island. They knew
    one of them had committed the crime, but not
    which one.
  • They also knew that the criminal was a Knight,
    and that the other two they questioned were not.
  • The investigators made a transcript of the
    statements made by each of the 3 inhabitants.
  • Using logic, did they identify A, B, or C as the
    guilty person?

3
  • On a distant island, there are 3 kinds of humans
    Knights, Knaves, and Normals.
  • A I am innocent
  • B That is true.
  • C B is not a normal.
  • Which one is the Knight and, therefore, the
    criminal?
  • Identify the possible solutions.
  • Identify the fact list.
  • Evaluate the possible solutions given the fact
    list (which includes what each said) and solve
    the puzzle

4
  • A I am innocent.
  • If A is the Knight,
  • B That is true.
  • If B is lying,
  • C B is not normal.
  • If C is lying,

5
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 and Hempels sophisticated version).
  • 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.

6
Part 2
  • Tales from the history of science

7
Cases of planetary misbehavior
  • A physicist of the Newtonian era took Newtons
    law of gravitation, N, the accepted initial
    conditions, C, and calculated the predicted path
    of the planet, Uranus. But the planet deviated
    from the calculated path.
  • Did our Newtonian physicist consider, that once
    established, the deviation of Uranus from its
    predicated path refutes the law, N?

8
  • Well, yes, a few did.
  • But more proposed that there was another, yet
    undiscovered planet whose gravitational pull
    explained the deviation in Uranus predicted
    path. Using Newtonian theory, they predicted
    where the planet would be, its mass, etc.
  • Was this prediction Ad hoc? How might we be able
    to decide if it was?
  • In this case, when they trained telescopes to the
    predicted region of the sky, they discovered the
    planet Neptune and claimed a victory for
    Newtonian theory!
  • Because Neptunes predicted path also deviated
    from what was predicted, they proposed another
    planet and discovered Pluto!

9
Cases of planetary misbehavior
10
Uh, oh! What to do about the peacocks tail?
  • As Darwin understood things, Natural Selection
    cannot select a trait that is disadvantageous
    to its bearer that compromises its survival
  • So what to do with all the ornaments that
    (predominantly) male members of various species
    are endowed?
  • The Peacocks tail
  • Antlers
  • Bright colors

11
Uh, oh! What to do about the peacocks tail?
  • It seemed that many such traits were not benign
    but actually put those so endowed at a distinct
    disadvantage
  • Its very hard for a peacock to take off, fly
    easily, and land
  • Young males with antlers often crash into trees,
    each other, buildings, and so forth
  • Bright colors seem to make an organism an easier
    target for prey
  • Apparent counter-examples to or falsifiers of
    evolution by Natural Selection!

12
Uh, oh! What to do about the peacocks tail?
13
Uh, oh! What to do about the peacocks tail?
14
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

15
Poppers Falsificationism
  • But, although this was seen as a major flaw with
    the geocentric model, 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.

16
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.

17
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.

18
Part 3
  • Poppers solution to
  • The problem of induction

19
Poppers explication and defense of
falsificationism
  1. Reiterate (in contemporary terms) why inductive
    reasoning cannot be justified.
  2. To justify it would require a principle of
    induction, itself known a priori or being the
    conclusion of a sound argument. We do not and
    cannot have either.
  3. Even a probabilistic understanding of inductive
    reasoning would require its own principle of
    induction, and suffers from the same problems.
  4. So if (as Hume claimed) it might turn out that
    psychologists report scientists (and the rest of
    us) use induction, this is not itself an
    epistemological issue.

20
Poppers explication and defense of
falsificationism
  • Reject 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 description the
    latter concerned with questions of justification
    or validity i.e., is normative rather than
    descriptive
  • Reiterate the discovery/justification
    distinction However a scientist arrives at a
    hypothesis, all that philosophy of science
    (epistemology) is concerned with is whether the
    hypothesis is justified.

21
  • Provide an alternative to inductivist accounts of
    scientific reasoning and, in particular, a
    deductivist account of the testing of hypotheses.
  • Make use of the fact that while the logic of
    confirmation involves a deductively invalid
    argument form, and is beset by the (old?) problem
    of induction, the logic of falsification involves
    a deductively valid argument form and avoids the
    problem of induction altogether.
  • If H, then I
  • Not I
  • --------------
  • Not H

22
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!

23
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

24
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?
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