I’ve had a few “Duh!” moments of late

1. I’ve had a few “Duh!” moments of late The online quiz for today’s 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! We’ll 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 wasn’t in the film – and second, that’s 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. You’re just up one point.

2. Let’s 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. Let’s 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. Let’s 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. Let’s 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. Let’s talk essays… Back to the beads… So after you’ve 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? It’s 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 isn’t as strong as it might first appear.

7. Let’s 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. Hempel’s 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. Hempel’s 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 doesn’t, why not? Which can he test directly? Which indirectly?

14. Hempel’s 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. Hempel’s 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 It’s 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 priest’s route so women in the 1st division don’t see him will result in a drop in cases. • The priest’s 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 woman’s position in delivery (here the 2 wards differ), then changing women’s positions in the 1st division should lead to a drop in cases. • Women’s 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 • 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. • Why think of cadaveric material as a likely cause? • His colleagues illness was just like that of women who died of “childbed” fever. • 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. Hempel’s 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) • I’ve 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 Kekule’s 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 there’s the “legend” of an apple falling on Newton’s head…

31. Revisiting discovery • Wasn’t 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”. Here’s 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.