I

1
Ive had a few Duh! moments of late

• The online quiz for todays reading included
  questions about auxiliary assumptions as Hempel
  argued for them but the editor of our volume
  cut out the 2 relevant paragraphs I should have
  caught it! Well cover the issue.
• On question 20 of the test, you were correct if
  you did not choose (b) concerning evidence of
  writing. First of all, it wasnt in the film
  and second, thats because it comes much later!
  So your TA will give you the point if you lost
  one for not choosing it and if you did choose
  it, no penalty. Youre just up one point.

2
Lets talk essays

• As the material of one link suggests,
  philosophical papers often include an argument
  for a thesis.
• But, in this essay, your priority is explicating
  the reasoning/argument of the scientist or
  scientists on whom you focus how they reasons
  from an artifact they can observe to the
  existence of some cognitive (mental) capacity in
  an ancestor group they cannot observe.
• You are asked to evaluate the reasoning, but that
  is not the main project of this first essay.

3
Lets talk essays

• You may or may not include a brief introduction.
  Do so when you believe your analysis needs some
  framing
• Describe the artifact you have chosen clearly
  (you need not add specific dates proposed for its
  age, or place it was found) just what
  scientists take it to be (e.g., a decorative
  bead, a tool for hunting large animals, a
  painting)
• Then outline (not literally) their argument for
  a hypothesis concerning some mental capacity they
  think it points to (serves as evidence of).

4
Lets talk essays

• Back to the beads
• Artifact shells that have been uniformly
  polished and pierced to allow for
  hanging/stringing and many of them in particular
  spots.
• Evidence that these people were willing to spend
  thousands of hours engaging in a project without
  (at least obvious) survival value.
• Evidence of how they were made, and thus how
  labor-intensive the process of making them
• Hypothesis the beads were used to reflect
  social identity perhaps I am a member of this
  tribe

5
Lets talk essays

• Back to the beads
• Surely, they serve as evidence for a hypothesis
  that at this time in our history, humans were
  engaging in activities that demonstrate
  creativity and/or artistic expression and,
  perhaps, interest in symbolizing social identity
• But you might think (as I do) that the move to I
  am a mother of 3 is something of a leap.

6
Lets talk essays

• Back to the beads
• So after youve laid out the argument for the
  hypothesis being offered, you are asked to
  evaluate it.
• How does one go about doing this when, as in this
  case, we cannot directly observe the folks we are
  hypothesizing about?
• Its not enough that the hypothesis would
  explain the artifact
• But ask, rather, whether there are equally
  plausible (even one) alternative hypotheses that
  would work equally well. Then the reasoning isnt
  as strong as it might first appear.

7
Lets talk essays

• Back to the beads
• So, in the case of the beads, it seems that to
  assume they represented social identity beyond
  just something like I belong to this group is
  not really that strong. For alternatives
• The beads were actually used as barter, and had
  no more meaning than that
• Or the beads just signaled group membership
• Exist.
• And perhaps the social identity hypothesis relies
  too much on imposing our way of thinking today on
  early ancestors

8
Narrow (or naïve) inductivism

• Collect facts ? Categorize them ? Generalize to a
  hypothesis ? Test the hypothesis
• Hypothesis
• Induction Deduction
• Facts Facts

9
Problems

• The problem of induction (which, as empiricists,
  they should have known about!)
• More importantly, the mismatch between their
  model of discovery and actual historical cases of
  discovery, which seem to involve (not all at once
  but regularly)
• Luck
• Accidents
• Crazy reasoning
• How to fix these problems?
• One answer give up on an account of discovery
  of hypotheses or theories
• Focus instead on the logic of testing them once
  discovered emphasizing, again, logical
  reasoning and experience

10
New approach Distinguishing between the contexts
of discovery and justification

• Context of discovery
• The reasoning involved in the discovery of
  hypotheses or theories.
• Inductive? Creative? Luck? Synthesis?
• Any such account should be compatible with the
  history and current practice of science.
• Context of justification
• The reasoning involved in the testing of
  hypotheses or theories.
• Deductive, inductive, or something else?
• Any such account should be compatible with the
  history and current practice of science.

11
Hempel The logic of confirmation

• Ignaz Semmelweis
• The savior of mothers
• In 1847, identified putrid material and bad
  hygiene on the part of medical practitioners as
  implicated in childbed fever
• His findings were rejected by the medical
  community
• He suffered a nervous breakdown and was
  institutionalized
• Death reported as a suicide turned out to be
  murder

12
Hempels inductivism (scientific reasoning is
inductive in a wider sense)

• The identification or recognition of a problem
  (something to be explained)
• Consideration or generation of hypotheses
• Consideration are proposed hypotheses
  compatible with other things we know?
• Generation creativity, accidents, luck NOT
  induction or any other logical process
• Choosing one or more hypotheses to test (figuring
  out how)
• Tests
• Confirmation (inductive!) or falsification (more
  complicated than logical argument form suggests)

13
Hempels inductivism (scientific reasoning is
inductive in a wider sense)

• The identification or recognition of a problem
  the case of Semmelweis as representative
• One general problem Childbed fever
• A more specific problem Why the rates were much
  higher in Division One than in Division Two of
  the same hospital? (In a sense providing a
  natural experiment)
• Consideration or generation of hypotheses
• Some are already current
• Telluric influences, crowding, diet, examination
  techniques, dread caused by the priest, delivery
  position?
• Which ones does he test? And of those he doesnt,
  why not? Which can he test directly? Which
  indirectly?

14
Hempels inductivism

• If childbed fever is caused by telluric
  influences, women in both divisions should
  contract it at equal rates, as should women who
  deliver in home or in the street.
• Women who deliver in the second division, as well
  as women who deliver at home and in the street,
  do not contract childbed fever at the same rate
  as those in the first division
• --------------------------------------------------
  --
• So, childbed fever is not caused by telluric
  influences.

15
Hempels inductivism

• The diets are the same in the two divisions
• Midwives in the 2nd division use the same
  examination techniques as med students in the 1st
  division
• Its not due to overcrowding in the 1st division,
  as it is the 2nd that is overcrowded

16
Hempel The logic of confirmation

• If childbed fever is caused by dread brought on
  by the priest bringing last rites (here the 2
  wards differ), then changing the priests route
  so women in the 1st division dont see him will
  result in a drop in cases.
• The priests route is changed.
• There is no drop in cases
• --------------------------------------------------
  --
• Childbed fever is not caused by dread brought on
  by the priest bringing last rites.

17
Hempel The logic of confirmation

• If H, then I
• Not I
• ------------------
• Not H
• Modus Tollens
• Deductively valid
• Will come to be called the logic of
  falsification.
• Hempel is himself focusing on the logic of
  confirmation.

18
Hempel The logic of confirmation

• If childbed fever is caused by a womans position
  in delivery (here the 2 wards differ), then
  changing womens positions in the 1st division
  should lead to a drop in cases.
• Womens positions in the 1st ward are changed.
• There is no drop in cases
• --------------------------------------------------
  --
• Childbed fever is not caused by delivery
  position.
• Modus Tollens again.

19
Hempel The logic of confirmation

1. Semmelweis arrives at his first confirmed
   hypothesis because of an accident the poisoning
   of a surgical colleague whose skin was punctured
   by a scalpel during an autopsy.
2. Why think of cadaveric material as a likely
   cause?
3. His colleagues illness was just like that of
   women who died of childbed fever.
4. As importantly, only women in the first division
   were examined by medical students directly after
   the students performed autopsies and did not
   wash their hands.

20
Hempel The logic of confirmation

• If childbed fever is caused by cadaveric
  material, then if medical students wash their
  hands in a solution of chlorinated lime, there
  will be a drop in the number of cases.
• Medical students wash their hands in the
  solution.
• There is a drop in cases of childbed fever.
• --------------------------------------------------
  --
• So, childbed fever is caused by cadaveric
  material.

21
Hempels initial schema

• If H, then I1, I2 and In
• I1, I2 and In
• -----------------------------------
• H
• Why is this form of argument inductive?
• However many confirmations the hypothesis enjoys,
  these are finite in number, and can only show
  that some hypothesis which is a generalization
  or universal statement is probable.
• We have the same gap that occurs in empirical
  generalizations though the order of reasoning
  is reversed!
• And, of course, it turns out the Semmelweis
  initial hypothesis is wrong (or at least just
  partial)

22
Hempel on the problems of confirmation

• Yes, confirmation can only demonstrate the
  probability of a hypothesis
• But every positive test is one which opened the
  possibility that the hypothesis would be
  falsified.
• The more confirmations a hypothesis enjoys, the
  more warranted we are in (provisionally)
  accepting it as the basis for further research.
• Moreover deductive logic has its limits as well
• Even in mathematics or formal logic,
  deductively valid arguments or proofs do not
  themselves dictate any specific conclusion
  indeed, an infinite number of results will follow
  logically.

23
Hempel on the problems of confirmation

• Moreover deductive logic has its limits as well
• In logic, for example, we can prove the
  following
• P
• ---
• P or Q (or is inclusive in logic at least one
  is true)
• And from P or Q, we can prove P or Q or R

24
Hempel on the problems of falsification

• Moreover deductive logic as used in science has
  has a second problem.
• Consider the deductively valid argument form of
  the logic of falsification (Modus Tollens)
• If P, then Q or If H, then I
• Not Q Not I
• --------------- --------------
• Not P Not H

25
Hempel on the problems of confirmation

• Imagine that the experiment went differently
• If childbed fever is caused by cadaveric
  material, then if medical students wash their
  hands in a solution of chlorinated lime, there
  will be a drop in the number of cases.
• There is no drop.
• --------------------------------------------------
  --
• Childbed fever is not caused by cadaveric
  material
• but should we conclude that?
• After all, there were good reasons to believe it
  was.

26
The logic of falsification

• If childbed fever is caused by cadaveric
  material, then if medical students wash their
  hands in a solution of chlorinated lime, there
  will be a drop in the number of cases.
• What might we ask?
• Did the medical students wash their hands?
• Did they wash their hands after examining each
  patient?
• Was the solution strong enough?
• Does chlorinated lime kill whatever it is that
  cadaveric material contains and causes childbed
  fever?

27
Hempel Getting a better understanding of the
logic of testing

• It is never just H that yields the prediction I
• Auxiliary assumptions such as
• Ceteris paribus (all things being equal)
• Ive identified all the variables that might
  affect the outcome of the experiment
• Lime solution can kill the infectious agents that
  cause childbed fever Students washed their
  hands
• If (H A1) (A2 and An) then I.
• Not I
• ---------------------------------------------
• Not (H A1) (A2 and An)

28
Complications in the logic of testing

• It is never just H that yields the prediction I
• A historical case.
• Tycho Brahe reasoned
• If the Copernican hypothesis is true, then we
  should observe stellar parallax (a change in the
  angle of a given star to an observer as the earth
  moves).
• We do not observe stellar parallax.
• -------------------------------------------------
  -----
• So, the Copernican hypothesis is false.

29
Complications in the logic of testing

• If the Copernican hypothesis is true, then we
  should observe stellar parallax (a change in the
  angle of a given star to an observer as the earth
  moves).
• A The stars are close enough that stellar
  parallax would be seen by the naked eye.
• We do not observe stellar parallax.
• -------------------------------------------------
  -----
• So, not (H and A)!

30
Back to the logic of discovery

• Hempel cites examples, such as Kekules discovery
  of the structure of the Benzene molecule, as
  evidence that there is no logic to discovery (nor
  given testing need we worry about that)
• Other examples that support him
• Alfred Wallace, who also came up with natural
  selection as a mechanism that allows evolution,
  arrived at the hypothesis during a fever induced
  by Malaria
• Then theres the legend of an apple falling on
  Newtons head

31
Revisiting discovery

• Wasnt there a logic to Semmelweis reasoning
  and is his reasoning idiosyncratic?
• Problem ? Consider hypotheses ? Reject those
  incompatible with other things we know ? Devise
  tests of those that survive the first round ?
  Accept or reject on the basis of success or
  failure of predictions ? Revise or abandon
  hypotheses earlier confirmed if new evidence
  warrants it
• Sometimes, accidents only lead a well prepared
  mind to a hypothesis

32
Popper the logic of falsification

• 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
  important logic involved in justification or
  testing is deductive and, specifically, the logic
  of falsification (Modus Tollens).
• Re the distinction between psychology and
  epistemology. Heres the deal
• Popper thinks Hume and others got into trouble by
  focusing on the empirical question of how, in
  fact, people reason rather than on how they
  should.