Historical Science M ethodology and D ifferences from E xperim - - PowerPoint PPT Presentation

C arol E . C leland C arol E . C leland Philosophy D epartm ent Philosophy D epartm ent C enter for A strobiology C enter for A strobiology U niversity of C olorado (B oulder) U niversity of C olorado (B oulder)

Historical Science

M ethodology and D ifferences from E xperim ental S cience

O VE RVIE W O VE RVIE W

• D ifferences in the m

ethodology of classical experim ental science and prototypical historical science: two different patterns of evidential reasoning.

• T he role of com

m

• n cause explanation in the evaluation
• f historical hypotheses.
• T he Principle of the C om

m

• n C ause and the

asym m etry of overdeterm ination.

• T he priority of com

m

• n cause over separate causes

explanation in historical science.

• D ifferences in the m

ethodology of classical experim ental science and prototypical historical science: two different patterns of evidential reasoning.

• T he role of com

m

• n cause explanation in the evaluation
• f historical hypotheses.
• T he Principle of the C om

m

• n C ause and the

asym m etry of overdeterm ination.

• T he priority of com

m

• n cause over separate causes

explanation in historical science.

T he structure of C lassical E xperim ental S cience T he structure of C lassical E xperim ental S cience

• Focus: Is on a single (som

etim es com plex) hypothesis which typically has the form

• f a universal generalization

(A ll C ’s are E ’s).

• C entral Research A ctivity: C onsists in repeatedly

bringing about the test conditions specified by the hypothesis and controlling for extraneous conditions that m ight be responsible for false positives and false negatives.

• Focus: Is on a single (som

etim es com plex) hypothesis which typically has the form

• f a universal generalization

(A ll C ’s are E ’s).

• C entral Research A ctivity: C onsists in repeatedly

bringing about the test conditions specified by the hypothesis and controlling for extraneous conditions that m ight be responsible for false positives and false negatives.

T he E xperim ental Program vs. S olitary E xperim ent T he E xperim ental Program vs. S olitary E xperim ent

• Failed predictions: do not result in the rejection of

hypotheses; they are best interpreted as attem pts to protect the hypothesis from false negatives.

• S uccessful predictions: A re not followed by risky tests

(in Popper’s sense); they are best interpreted as attem pts to protect the hypothesis from false positives.

• A cceptance/ rejection of a hypothesis: occurs only

after a hypothesis is subjected to a series of experim ents controlling for plausible auxiliary assum ptions that could explain predictive successes and predictive failures.

• Failed predictions: do not result in the rejection of

hypotheses; they are best interpreted as attem pts to protect the hypothesis from false negatives.

• S uccessful predictions: A re not followed by risky tests

(in Popper’s sense); they are best interpreted as attem pts to protect the hypothesis from false positives.

• A cceptance/ rejection of a hypothesis: occurs only

after a hypothesis is subjected to a series of experim ents controlling for plausible auxiliary assum ptions that could explain predictive successes and predictive failures.

T he structure of Prototypical H istorical S cience T he structure of Prototypical H istorical S cience

Focus:Is on proliferating m ultiple, rival hypotheses to explain a puzzling body of traces encountered in field world. C entral Research A ctivity: C onsists in searching for a ‘sm

• king gun’ a trace(s) that sets apart
• ne or m
• re hypotheses as providing a better

explanation for the observed traces than the

• thers.

Focus:Is on proliferating m ultiple, rival hypotheses to explain a puzzling body of traces encountered in field world. C entral Research A ctivity: C onsists in searching for a ‘sm

• king gun’ a trace(s) that sets apart
• ne or m
• re hypotheses as providing a better

explanation for the observed traces than the

• thers.

A C ase S tudy

T he A lvarez H ypothesis

A C ase S tudy

T he A lvarez H ypothesis

• T wo pronged hypotheses: im

pact, extinction

• Initially m

any different explanations for the end- C retaceous m ass extinction: pandem ic, evolutionary senescence, clim ate change, supernova, volcanism , and m eteorite Im pact.

• D iscovery of an iridium

anom aly (“sm

• king gun”) in

K -T boundary sedim ents narrowed it down to two possibilities: volcanism and m eteorite im pact. D iscovery of extensive quantities of a rare form

• f

shocked m ineral subsequently cinched the case for im pact over volcanism .

• T wo pronged hypotheses: im

pact, extinction

• Initially m

any different explanations for the end- C retaceous m ass extinction: pandem ic, evolutionary senescence, clim ate change, supernova, volcanism , and m eteorite Im pact.

• D iscovery of an iridium

anom aly (“sm

• king gun”) in

K -T boundary sedim ents narrowed it down to two possibilities: volcanism and m eteorite im pact. D iscovery of extensive quantities of a rare form

• f

shocked m ineral subsequently cinched the case for im pact over volcanism .

T he E valuation of H istorical H ypotheses T he E valuation of H istorical H ypotheses

• N ot grounded in prediction:
• H istorical predictions are not ‘risky’ in Popper’s

sense; too m any highly plausible extraneous conditions (e.g., iridium poor m eteorite, geological processes, unrepresentative sam ples) capable of defeating them .

• Predictions are typically vague, e.g., Ward’s

‘prediction’ about C retaceous am m

• nites; they

serve m

• re as guides for looking for a sm
• king gun

than predictions.

• N ot grounded in prediction:
• H istorical predictions are not ‘risky’ in Popper’s

sense; too m any highly plausible extraneous conditions (e.g., iridium poor m eteorite, geological processes, unrepresentative sam ples) capable of defeating them .

• Predictions are typically vague, e.g., Ward’s

‘prediction’ about C retaceous am m

• nites; they

serve m

• re as guides for looking for a sm
• king gun

than predictions.

T he E valuation of H istorical H ypotheses(cont.) T he E valuation of H istorical H ypotheses(cont.)

• A hypothesis m

ay be rejected on the basis of evidence that does not refute it, e.g., the contagion hypothesis for the end-C retaceous extinctions.

• T he acceptance of a hypothesis does not

require a successful prediction, e.g., the iridium anom aly was not and could not have been predicted or retrodicted.

• A hypothesis m

ay be rejected on the basis of evidence that does not refute it, e.g., the contagion hypothesis for the end-C retaceous extinctions.

• T he acceptance of a hypothesis does not

require a successful prediction, e.g., the iridium anom aly was not and could not have been predicted or retrodicted.

T he E valuation of H istorical H ypotheses(cont.) T he E valuation of H istorical H ypotheses(cont.)

• G rounded in explanatory power:
• H ypotheses are accepted and rejected in virtue of

their power to explain (vs.predict) puzzling bodies of traces discovered through field work.

• T he A lvarez hypothesis explains an otherwise

puzzling association (correlation) am

• ng traces better

than any of its rivals. It is for this reason that it is viewed as ‘confirm ed’ and its rivals are no longer seriously entertained by scientists.

• G rounded in explanatory power:
• H ypotheses are accepted and rejected in virtue of

their power to explain (vs.predict) puzzling bodies of traces discovered through field work.

• T he A lvarez hypothesis explains an otherwise

puzzling association (correlation) am

• ng traces better

than any of its rivals. It is for this reason that it is viewed as ‘confirm ed’ and its rivals are no longer seriously entertained by scientists.

C om m

• n C ause explanation

C om m

• n C ause explanation
• C om

m

• n cause explanations and narrative explanations, e.g.,

sexing a T . rex.

• Reichenbach’s epistem

ic Principle of the C om m

• n C ause:

seem ingly im probable associations (correlations or sim ilarities) am

• ng traces are best explained by reference to a

com m

• n cause.
• Presupposes an ostensibly m

etaphysical claim about the tem poral structure of causal relations in our universe: m

• st

(not all) events form causal forks opening from past to future (leave m any traces in the future).

• C om

m

• n cause explanations and narrative explanations, e.g.,

sexing a T . rex.

• Reichenbach’s epistem

ic Principle of the C om m

• n C ause:

seem ingly im probable associations (correlations or sim ilarities) am

• ng traces are best explained by reference to a

com m

• n cause.
• Presupposes an ostensibly m

etaphysical claim about the tem poral structure of causal relations in our universe: m

• st

(not all) events form causal forks opening from past to future (leave m any traces in the future).

T he A sym m etry of O verdeterm ination T he A sym m etry of O verdeterm ination

• A tim

e asym m etry of causation: M ost local events

• verdeterm

ine their past causes (because the latter typically leave extensive and diverse effects)and underdeterm ine their future effects (because they rarely constitute the total cause of an effect)

• M uch easier to infer an ancient volcanic eruption

than a near future volcanic eruption.

• A tim

e asym m etry of causation: M ost local events

• verdeterm

ine their past causes (because the latter typically leave extensive and diverse effects)and underdeterm ine their future effects (because they rarely constitute the total cause of an effect)

• M uch easier to infer an ancient volcanic eruption

than a near future volcanic eruption.

T he A sym m etry of O verdeterm ination (cont.) T he A sym m etry of O verdeterm ination (cont.)

• Physical source is controversial but it characterizes all wave

(radiativeasym m etry)and particle (2nd law of therm

• dynam

ics) phenom ena; an objective and pervasive physical feature of world.

• Physically (vs. logically or strictly m

etaphysically) grounds the Principle of the C om m

• n C ause and the m

ethodology of historical natural science.

• A sserts that the present is filled with epistem

ically

• verdeterm

ining traces of the past; hence one can never com pletely rule out finding a sm

• king gun for any scientific

hypothesis about the past.

• Physical source is controversial but it characterizes all wave

(radiativeasym m etry)and particle (2nd law of therm

• dynam

ics) phenom ena; an objective and pervasive physical feature of world.

• Physically (vs. logically or strictly m

etaphysically) grounds the Principle of the C om m

• n C ause and the m

ethodology of historical natural science.

• A sserts that the present is filled with epistem

ically

• verdeterm

ining traces of the past; hence one can never com pletely rule out finding a sm

• king gun for any scientific

hypothesis about the past.

T he priority of com m

• n cause over

separate causes explanations T he priority of com m

• n cause over

separate causes explanations

• T he asym

m etry of overdeterm ination(A of O D ) does not guarantee that every im probable association am

• ng traces is due

to a last com m

• n cause; it is a statistical/ probabilistic claim

.

• T he A of O D does suggest that im

probable associations am

• ng traces are m
• re likely to be the result of a com

m

• n cause

than separate causes

• In the absence of special theoretical or local background

inform ation, historical natural scientists exhibit a preference for com m

• n cause over separate causes explanations.
• T he asym

m etry of overdeterm ination(A of O D ) does not guarantee that every im probable association am

• ng traces is due

to a last com m

• n cause; it is a statistical/ probabilistic claim

.

• T he A of O D does suggest that im

probable associations am

• ng traces are m
• re likely to be the result of a com

m

• n cause

than separate causes

• In the absence of special theoretical or local background

inform ation, historical natural scientists exhibit a preference for com m

• n cause over separate causes explanations.

A C ase S tudy

T he end-Perm ian E xtinction (245 m ya)

A C ase S tudy

T he end-Perm ian E xtinction (245 m ya)

• O n the basis of an initial body of correlated traces,

paleontologists conjectured that there was a single, prolonged extinction event lasting m illions of years, and they proliferated a num ber of rival com m

• n cause

hypotheses to explain it.

• A s they accum

ulated m

• re evidence it becam

e clear that there were actually two extinction pulses separated by a period of around 10 m illion years.

• O n the basis of an initial body of correlated traces,

paleontologists conjectured that there was a single, prolonged extinction event lasting m illions of years, and they proliferated a num ber of rival com m

• n cause

hypotheses to explain it.

• A s they accum

ulated m

• re evidence it becam

e clear that there were actually two extinction pulses separated by a period of around 10 m illion years.

T he end-Perm ian E xtinction (cont.) T he end-Perm ian E xtinction (cont.)

• In the absence of specific theoretical reasons or em

pirical evidence that the end-Perm ian extinction was produced by separate causes, paleontologists opted for rival com m

• n cause

hypotheses.

• H aving acquired com

pelling local em pirical evidence that there were two extinction events, they opted for separate causes.

• T hey then returned their focus to com

m

• n causes: separate

com m

• n causes of the two extinctions and the possibility that

both resulted from an earlier com m

• n cause (e.g., Pangaea)
• In the absence of specific theoretical reasons or em

pirical evidence that the end-Perm ian extinction was produced by separate causes, paleontologists opted for rival com m

• n cause

hypotheses.

• H aving acquired com

pelling local em pirical evidence that there were two extinction events, they opted for separate causes.

• T hey then returned their focus to com

m

• n causes: separate

com m

• n causes of the two extinctions and the possibility that

both resulted from an earlier com m

• n cause (e.g., Pangaea)

C onclusion C onclusion

• Researchers in historical natural science exhibit a

preference, all other things being equal, for com m

• n

cause explanation over separate causes explanation

• T he A of O D underwrites this preference
• T he objectivity and rationality of the m

ethodology of historical natural science is grounded in a global physical feature of our universe, as opposed to a logical relation between evidence & hypothesis

• Researchers in historical natural science exhibit a

preference, all other things being equal, for com m

• n

cause explanation over separate causes explanation

• T he A of O D underwrites this preference
• T he objectivity and rationality of the m

ethodology of historical natural science is grounded in a global physical feature of our universe, as opposed to a logical relation between evidence & hypothesis

References References

• “Prediction and Explanation in Historical Natural Science” (forthcoming in

British Journal of Philosophy of Science)

• “Philosophical issues in natural history and its historiography” in Tucker,
• A. (ed), Blackwell Companions to Philosophy: A Companion to the

Philosophy of History and Historiography. Oxford: Blackwell Pub. (2009), pp. 44-62.

• “Methodological and Epistemic Differences Between Historical Science and

Experimental Science,” Philosophy of Science 69, (2002), pp. 474-496.

• “Reply to Kevin Kilty’s ‘Comment on: Historical science, experimental

science, and the scientific method’,” Geology 30, (2002), pp. 951-952.

• “Reply to R. J. Bailey’s ‘ Comment on: Historical science, experimental

science, and the scientific method’,” Geology 30, (2002), pp. 953-954.

• “Historical science, experimental science, and the scientific method,” Geology

29, (2001), pp. 987-990.

• “Prediction and Explanation in Historical Natural Science” (forthcoming in

British Journal of Philosophy of Science)

• “Philosophical issues in natural history and its historiography” in Tucker,
• A. (ed), Blackwell Companions to Philosophy: A Companion to the

Philosophy of History and Historiography. Oxford: Blackwell Pub. (2009), pp. 44-62.

• “Methodological and Epistemic Differences Between Historical Science and

Experimental Science,” Philosophy of Science 69, (2002), pp. 474-496.

• “Reply to Kevin Kilty’s ‘Comment on: Historical science, experimental

science, and the scientific method’,” Geology 30, (2002), pp. 951-952.

• “Reply to R. J. Bailey’s ‘ Comment on: Historical science, experimental

science, and the scientific method’,” Geology 30, (2002), pp. 953-954.

• “Historical science, experimental science, and the scientific method,” Geology

29, (2001), pp. 987-990.