I’ve had a few “Duh!” moments of late

The online quiz for today’s reading included The online quiz for today’s reading included questions about “auxiliary assumptions” as questions about “auxiliary assumptions” as Hempel argued for them – but the editor of our Hempel argued for them – but the editor of our volume volume cut outcut out the 2 relevant paragraphs… I the 2 relevant paragraphs… I should have caught it! We’ll cover the issue.should have caught it! We’ll cover the issue.

On question 20 of the test, you were correct if On question 20 of the test, you were correct if you did not choose (b) concerning evidence of you did not choose (b) concerning evidence of writing. First of all, it wasn’t in the film – and writing. First of all, it wasn’t in the film – and second, that’s because it comes *much* later! second, that’s because it comes *much* later! So your TA will give you the point if you lost one So your TA will give you the point if you lost one for not choosing it … and if you did choose it, no for not choosing it … and if you did choose it, no penalty. You’re just up one point.penalty. You’re just up one point.

Let’s talk essays… As the material of one link suggests, As the material of one link suggests,

philosophical papers often include an philosophical papers often include an argument for a thesis. argument for a thesis.

But, in this essay, your priority is explicating But, in this essay, your priority is explicating the reasoning/argument of the scientist or the reasoning/argument of the scientist or scientists on whom you focus – how they scientists on whom you focus – how they reasons from an artifact they can observe to reasons from an artifact they can observe to the existence of some cognitive (mental) the existence of some cognitive (mental) capacity in an ancestor group they cannot capacity in an ancestor group they cannot observe.observe.

You are asked to evaluate the reasoning, but You are asked to evaluate the reasoning, but that is not the main project of this first essay.that is not the main project of this first essay.

Let’s talk essays… You may or may not include a brief You may or may not include a brief

introduction. Do so when you believe your introduction. Do so when you believe your analysis needs some “framing”…analysis needs some “framing”…

Describe the artifact you have chosen clearly Describe the artifact you have chosen clearly (you need not add specific dates proposed for (you need not add specific dates proposed for its age, or place it was found); just what its age, or place it was found); just what scientists take scientists take itit to be (e.g., a decorative bead, to be (e.g., a decorative bead, a tool for hunting large animals, a painting…)a tool for hunting large animals, a painting…)

Then outline (not literally…) their argument for Then outline (not literally…) their argument for a hypothesis concerning some mental capacity a hypothesis concerning some mental capacity they think it points to (serves as evidence of).they think it points to (serves as evidence of).

Let’s talk essays… Back to the beads…Back to the beads… Artifact: shells that have been uniformly polished and Artifact: shells that have been uniformly polished and

“pierced” to allow for hanging/stringing… and many of “pierced” to allow for hanging/stringing… and many of them in particular spots.them in particular spots.

Evidence that these people were willing to spend Evidence that these people were willing to spend thousands of hours engaging in a project without (at thousands of hours engaging in a project without (at least obvious) survival value.least obvious) survival value.

Evidence of how they were made, and thus how Evidence of how they were made, and thus how labor-intensive the process of making themlabor-intensive the process of making them

Hypothesis: the beads were used to reflect “social Hypothesis: the beads were used to reflect “social identity”… perhaps “I am a member of this tribe”identity”… perhaps “I am a member of this tribe”

Let’s talk essays… Back to the beads…Back to the beads… Surely, they serve as evidence for a Surely, they serve as evidence for a

hypothesis that at this time in our history, hypothesis that at this time in our history, humans were engaging in activities that humans were engaging in activities that demonstrate creativity and/or artistic demonstrate creativity and/or artistic expression… and, perhaps, interest in expression… and, perhaps, interest in symbolizing social identitysymbolizing social identity

But you might think (as I do) that the move to “I But you might think (as I do) that the move to “I am a mother of 3”… is something of a leap.am a mother of 3”… is something of a leap.

Let’s talk essays… Back to the beads…Back to the beads… So after you’ve laid out the argument for the So after you’ve laid out the argument for the

hypothesis being offered, you are asked to evaluate hypothesis being offered, you are asked to evaluate it.it.

How does one go about doing this when, as in this How does one go about doing this when, as in this case, we cannot directly observe the folks we are case, we cannot directly observe the folks we are hypothesizing about?hypothesizing about?

It’s not enough that the hypothesis “would” explain It’s not enough that the hypothesis “would” explain the artifact…the artifact…

But ask, rather, whether there are equally plausible But ask, rather, whether there are equally plausible (even one) alternative hypotheses that would work (even one) alternative hypotheses that would work equally well. Then the reasoning isn’t as strong as it equally well. Then the reasoning isn’t as strong as it might first appear.might first appear.

Let’s talk essays… Back to the beads…Back to the beads… So, in the case of the beads, it seems that to assume So, in the case of the beads, it seems that to assume

they represented social identity beyond just they represented social identity beyond just something like “I belong to this group” is not really something like “I belong to this group” is not really that strong. For alternatives:that strong. For alternatives: The beads were actually used as barter, and had no more The beads were actually used as barter, and had no more

meaning than thatmeaning than that Or the beads just signaled group membership…Or the beads just signaled group membership…

Exist.Exist. And perhaps the social identity hypothesis relies too And perhaps the social identity hypothesis relies too

much on imposing much on imposing ourour way of thinking today on early way of thinking today on early ancestors…ancestors…

“Narrow” (or naïve) inductivism

Collect facts → Categorize them → Generalize Collect facts → Categorize them → Generalize to a hypothesis → Test the hypothesisto a hypothesis → Test the hypothesis

HypothesisHypothesis

InductionInduction DeductionDeduction

FactsFacts Facts Facts

Problems

The problem of induction (which, as empiricists, they The problem of induction (which, as empiricists, they should have known about!)should have known about!)

More importantly, the mismatch between their model of More importantly, the mismatch between their model of discovery and actual historical cases of discovery, which discovery and actual historical cases of discovery, which seem to involve (not all at once but regularly)seem to involve (not all at once but regularly) LuckLuck AccidentsAccidents ““Crazy” reasoningCrazy” reasoning

How to fix these problems?How to fix these problems? One answer: give up on an account of “discovery” of One answer: give up on an account of “discovery” of

hypotheses or theorieshypotheses or theories Focus instead on the “logic” of testing them once Focus instead on the “logic” of testing them once

discovered – emphasizing, again, logical reasoning and discovered – emphasizing, again, logical reasoning and experienceexperience

New approach: Distinguishing between the New approach: Distinguishing between the contexts of discovery and justificationcontexts of discovery and justification

Context of discoveryContext of discovery The reasoning involved in the The reasoning involved in the discoverydiscovery of of

hypotheses or theories.hypotheses or theories. Inductive? Creative? Luck? Synthesis…?Inductive? Creative? Luck? Synthesis…? Any such account should be compatible with the Any such account should be compatible with the

history and current practice of science.history and current practice of science. Context of justificationContext of justification

The reasoning involved in the The reasoning involved in the testingtesting of hypotheses or of hypotheses or theories.theories.

Deductive, inductive, or something else?Deductive, inductive, or something else? Any such account should be compatible with the Any such account should be compatible with the

history and current practice of science.history and current practice of science.

Hempel: The logic of confirmationHempel: The logic of confirmation

Ignaz SemmelweisIgnaz Semmelweis““The savior of mothers”The savior of mothers”In 1847, identified “putrid” In 1847, identified “putrid”

material and bad hygiene material and bad hygiene on the part of medical on the part of medical practitioners as implicated practitioners as implicated in childbed feverin childbed fever

His findings were rejected by His findings were rejected by the medical communitythe medical community

He suffered a nervous He suffered a nervous breakdown and was breakdown and was institutionalizedinstitutionalized

Death reported as a suicide; Death reported as a suicide; turned out to be murderturned out to be murder

Hempel’s inductivism (scientific reasoning Hempel’s inductivism (scientific reasoning is inductive in a “wider sense”)is inductive in a “wider sense”)

1.1. The identification or recognition of a problem (something The identification or recognition of a problem (something to be explained)to be explained)

2.2. Consideration or generation of hypothesesConsideration or generation of hypotheses

Consideration: are proposed hypotheses compatible with Consideration: are proposed hypotheses compatible with other things we know?other things we know?

Generation: creativity, accidents, luck… NOT induction or Generation: creativity, accidents, luck… NOT induction or any other logical processany other logical process

3.3. Choosing one or more hypotheses to test (figuring out Choosing one or more hypotheses to test (figuring out how…)how…)

4.4. TestsTests

5.5. Confirmation (inductive!) or falsification (more Confirmation (inductive!) or falsification (more complicated than logical argument form suggests)complicated than logical argument form suggests)

Hempel’s inductivism (scientific reasoning Hempel’s inductivism (scientific reasoning is inductive in a “wider sense”)is inductive in a “wider sense”)

1.1. The identification or recognition of a problem: the case of The identification or recognition of a problem: the case of Semmelweis as representativeSemmelweis as representative

One general problem: Childbed feverOne general problem: Childbed feverA more specific problem: Why the rates were much A more specific problem: Why the rates were much higher in Division One than in Division Two of the higher in Division One than in Division Two of the same hospital? (In a sense providing a “natural same hospital? (In a sense providing a “natural experiment”)experiment”)

2.2. Consideration or generation of hypothesesConsideration or generation of hypotheses Some are already currentSome are already current

Telluric influences, crowding, diet, examination techniques, dread Telluric influences, crowding, diet, examination techniques, dread caused by the priest, delivery position…?caused by the priest, delivery position…?

3.3. Which ones does he test? And of those he doesn’t, why Which ones does he test? And of those he doesn’t, why not? Which can he test directly? Which indirectly?not? Which can he test directly? Which indirectly?

Hempel’s inductivismHempel’s inductivism

1.1. If childbed fever is caused by telluric influences, If childbed fever is caused by telluric influences, women in both divisions should contract it at women in both divisions should contract it at equal rates, as should women who deliver in equal rates, as should women who deliver in home or in the street.home or in the street.

2.2. Women who deliver in the second division, as Women who deliver in the second division, as well as women who deliver at home and in the well as women who deliver at home and in the street, do not contract childbed fever at the same street, do not contract childbed fever at the same rate as those in the first divisionrate as those in the first division

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So, childbed fever is not caused by telluric So, childbed fever is not caused by telluric influences.influences.

Hempel’s inductivism

The diets are the same in the two divisionsThe diets are the same in the two divisions

Midwives in the 2Midwives in the 2ndnd division use the same division use the same examination techniques as med students in examination techniques as med students in the 1the 1stst division division

It’s not due to overcrowding in the 1It’s not due to overcrowding in the 1stst division, division, as it is the 2as it is the 2ndnd that is overcrowded that is overcrowded

Hempel: The logic of confirmationHempel: The logic of confirmation

1.1. If childbed fever is caused by dread brought on If childbed fever is caused by dread brought on by the priest bringing last rites (here the 2 by the priest bringing last rites (here the 2 wards differ), then changing the priest’s route wards differ), then changing the priest’s route so women in the 1so women in the 1stst division don’t see him will division don’t see him will result in a drop in cases.result in a drop in cases.

2.2. The priest’s route is changed.The priest’s route is changed.3.3. There is no drop in casesThere is no drop in cases--------------------------------------------------------------------------------------------------------Childbed fever is not caused by dread brought on Childbed fever is not caused by dread brought on

by the priest bringing last rites.by the priest bringing last rites.

Hempel: The logic of confirmationHempel: The logic of confirmation

1.1. If If HH, then , then II2.2. Not Not II------------------------------------ Not Not HHModus TollensModus TollensDeductively validDeductively validWill come to be called “the logic of falsification.Will come to be called “the logic of falsification.Hempel is himself focusing on “the logic of Hempel is himself focusing on “the logic of

confirmation”.confirmation”.

Hempel: The logic of confirmationHempel: The logic of confirmation

1.1. If childbed fever is caused by a woman’s If childbed fever is caused by a woman’s position in delivery (here the 2 wards differ), position in delivery (here the 2 wards differ), then changing women’s positions in the 1then changing women’s positions in the 1stst division should lead to a drop in cases.division should lead to a drop in cases.

2.2. Women’s positions in the 1Women’s positions in the 1stst ward are ward are changed.changed.

3.3. There is no drop in casesThere is no drop in cases--------------------------------------------------------------------------------------------------------Childbed fever is not caused by delivery position.Childbed fever is not caused by delivery position.

Modus Tollens again.Modus Tollens again.

Hempel: The logic of confirmationHempel: The logic of confirmation

1.1. Semmelweis arrives at his first Semmelweis arrives at his first confirmedconfirmed hypothesis because of an hypothesis because of an accidentaccident … the … the poisoning of a surgical colleague whose skin poisoning of a surgical colleague whose skin was punctured by a scalpel during an autopsy.was punctured by a scalpel during an autopsy.

2.2. Why think of cadaveric material as a likely Why think of cadaveric material as a likely cause?cause?

1.1. His colleagues illness was just like that of women who His colleagues illness was just like that of women who died of “childbed” fever.died of “childbed” fever.

2.2. As importantly, only women in the first division were As importantly, only women in the first division were examined by medical students examined by medical students directly afterdirectly after the students the students performed autopsies… and did not wash their hands.performed autopsies… and did not wash their hands.

Hempel: The logic of confirmationHempel: The logic of confirmation

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

2.2. Medical students wash their hands in the Medical students wash their hands in the solution.solution.

3.3. There is a drop in cases of childbed fever.There is a drop in cases of childbed fever.

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So, childbed fever is caused by cadaveric material.So, childbed fever is caused by cadaveric material.

Hempel’s initial schema

If If HH, then , then II11, , II22… and … and IInn II11, , II22… and … and IInn

---------------------------------------------------------------------- HHWhy is this form of argument Why is this form of argument inductiveinductive??

However manyHowever many confirmations the hypothesis enjoys, these are finite confirmations the hypothesis enjoys, these are finite in number, and can only show that some hypothesis – which is a in number, and can only show that some hypothesis – which is a generalization or universal statement – is generalization or universal statement – is probableprobable..

We have the same We have the same gapgap that occurs in empirical generalizations… that occurs in empirical generalizations… though the “order” of reasoning is reversed!though the “order” of reasoning is reversed!

And, of course, it turns out the Semmelweis’ initial hypothesis is And, of course, it turns out the Semmelweis’ initial hypothesis is wrong (or at least just partial)wrong (or at least just partial)

Hempel on the problems of confirmation

1. 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.

2. 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.

Hempel on the problems of confirmation

2. 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’…

Hempel on the problems of falsification

3. 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 Qor If H, then INot Q Not I--------------- --------------Not P Not H

Hempel on the problems of confirmationHempel on the problems of confirmation

Imagine that the experiment went differently:Imagine that the experiment went differently:• If childbed fever is caused by cadaveric material, If childbed fever is caused by cadaveric material,

then if medical students wash their hands in a then if medical students wash their hands in a solution of chlorinated lime, there will be a drop solution of chlorinated lime, there will be a drop in the number of cases.in the number of cases.

• There is There is no no drop.drop.--------------------------------------------------------------------------------------------------------3.3. Childbed fever is Childbed fever is notnot caused by cadaveric caused by cadaveric

materialmaterial… … but but shouldshould we conclude that? we conclude that? After all, there were good reasons to believe it was.After all, there were good reasons to believe it was.

The logic of falsification

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

2.2. What might we ask?What might we ask?DidDid the medical students wash their hands? the medical students wash their hands?Did they wash their hands Did they wash their hands after examining each after examining each

patientpatient??Was the solution Was the solution strong enoughstrong enough??Does chlorinated lime Does chlorinated lime killkill whatever it is that whatever it is that

cadaveric material contains and causes childbed cadaveric material contains and causes childbed fever?fever?

Hempel: Getting a better Hempel: Getting a better understanding of the logic of testingunderstanding of the logic of testing

It is never just It is never just H H that yields the prediction that yields the prediction II Auxiliary assumptions such asAuxiliary assumptions such as

Ceteris paribus (all things being equal)Ceteris paribus (all things being equal) I’ve identified all the variables that might affect the I’ve identified all the variables that might affect the

outcome of the experimentoutcome of the experiment Lime solution can kill the infectious agents that cause Lime solution can kill the infectious agents that cause

childbed fever… Students washed their hands…childbed fever… Students washed their hands… [If ([If (HH & A & A1)1) & & (A(A22…… and A and Ann)] then I.)] then I. Not INot I------------------------------------------------------------------------------------------

Not (Not (HH & A & A11) &) & (A(A22…… and A and Ann))

Complications in the logic of testingComplications in the logic of testing

It is never just It is never just H H that yields the prediction that yields the prediction II A historical case.A historical case. Tycho Brahe reasoned:Tycho Brahe reasoned:1.1. If the Copernican hypothesis is true, then we If the Copernican hypothesis is true, then we

should observe stellar parallax (a change in should observe stellar parallax (a change in the angle of a given star to an observer as the the angle of a given star to an observer as the earth moves).earth moves).

2.2. We do not observe stellar parallax.We do not observe stellar parallax.------------------------------------------------------------------------------------------------------------So, the Copernican hypothesis is false.So, the Copernican hypothesis is false.

Complications in the logic of testing

1.1. If the Copernican hypothesis is true, then we If the Copernican hypothesis is true, then we should observe stellar parallax (a change in should observe stellar parallax (a change in the angle of a given star to an observer as the the angle of a given star to an observer as the earth moves).earth moves).

AA The stars are close enough that stellar The stars are close enough that stellar parallax would be seen by the naked eye.parallax would be seen by the naked eye.

1.1. We do not observe stellar parallax.We do not observe stellar parallax.

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So, not (H So, not (H andand A)! A)!

Back to the “logic” of discoveryBack to the “logic” of discovery

Hempel cites examples, such as Kekule’s Hempel cites examples, such as Kekule’s discovery of the structure of the Benzene discovery of the structure of the Benzene molecule, as evidence that there is molecule, as evidence that there is nono logic to logic to discovery (nor given testing need we worry discovery (nor given testing need we worry about that)about that)

Other examples that support him:Other examples that support him:Alfred Wallace, who also came up with natural Alfred Wallace, who also came up with natural

selection as a mechanism that allows evolution, selection as a mechanism that allows evolution, arrived at the hypothesis during a fever induced arrived at the hypothesis during a fever induced by Malaria…by Malaria…

Then there’s the “legend” of an apple falling on Then there’s the “legend” of an apple falling on Newton’s head…Newton’s head…

Revisiting discovery

Wasn’t there a logic to Semmelweis’ Wasn’t there a logic to Semmelweis’ reasoning and is his reasoning idiosyncratic?reasoning and is his reasoning idiosyncratic?

Problem Problem → → Consider hypotheses Consider hypotheses → → Reject Reject those incompatible with other things we those incompatible with other things we know know → → Devise tests of those that survive Devise tests of those that survive the first round the first round → → Accept or reject on the Accept or reject on the basis of success or failure of predictions basis of success or failure of predictions → → Revise or abandon hypotheses earlier Revise or abandon hypotheses earlier confirmed if new evidence warrants it…confirmed if new evidence warrants it…

Sometimes, “accidents” only lead a well Sometimes, “accidents” only lead a well prepared mind to a hypothesis…prepared mind to a hypothesis…

Popper: the logic of falsification

There is no “principle of induction” that will justify There is no “principle of induction” that will justify induction or an inductivist account of scientific induction or an inductivist account of scientific method/reasoningmethod/reasoning

Like Hempel, Popper emphasizes that there is no logic Like Hempel, Popper emphasizes that there is no logic of discovery, but only a logic of justification (testing)of discovery, but only a logic of justification (testing)

But, unlike Hempel, Popper argues that the important But, unlike Hempel, Popper argues that the important logic involved in justification or testing is logic involved in justification or testing is deductivedeductive and, specifically, the logic of falsification (Modus and, specifically, the logic of falsification (Modus Tollens).Tollens).

Re the distinction between “psychology” and Re the distinction between “psychology” and “epistemology”. Here’s the deal:“epistemology”. Here’s the deal: Popper thinks Hume and others got into trouble by Popper thinks Hume and others got into trouble by

focusing on the empirical question of how, in fact, people focusing on the empirical question of how, in fact, people reason… rather than on how they reason… rather than on how they shouldshould..