HISTORICAL SCIENCE AND THE INTELLIGENT DESIGN THEORY

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Common Cause Explanation The Search for a
Smoking Gun
Carol E. Cleland Philosophy Department Center for
Astrobiology University of Colorado (Boulder)
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OVERVIEW

• Myths about the scientific Method.
• Classical experimental science and prototypical
  historical science two different but equally
  rational and objective patterns of evidential
  reasoning.
• How evidence acquired through field work
  justifies historical hypotheses Common cause
  explanation and the search for a smoking gun.

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Part I

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Myths about the Scientific method

• Inductivism Scientists prove theories and
  hypotheses by a logical process of induction.

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Myths about the Scientific method

• Falsificationism Scientists falsify theories
  and hypotheses by using empirical evidence to
  refute them.

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The Logic of Prediction

• Toy Example

• Basic Concepts

• All copper expands when heated.
• If sample of copper 4 is heated, then it will
  expand
• (Heating copper sample 4)
• (Copper sample 4 will expand)

• 1. Hypothesis (H)
• (All Cs are Es)
• 2. Test Implication (I)
• (If x is a C, then x is an E.)
• Test Condition (C)
• 4. Prediction (E)

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The Logic of Evaluating the Results of an
Experiment

• Successful Prediction
• 1. If H, then I
• 2. I
• C. H
• Logical Fallacy affirming the consequent.
• (This is just another version of the problem of
  induction.)

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The Logic of Evaluating the Results of an
Experiment

• Failed Prediction
• 1. If H, then I
• 2. Not-I
• C. Not-H
• Valid Argument Form denying the consequent.
• (This explains the appeal of falsificationism.)

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The Terrible Truth about Falsificationism

• The form of the first premise in the previous
  argument is
• If H and A, then I
• (where A stands for a set of auxiliary
  assumptions a1, a2, , an about other
  conditions, known and unknown, about the actual
  experimental situation.)

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The Terrible Truth about Falsificationism
(continued)

• This changes the form of the argument to
• 1. If H and a1, a2, , an, then I
• 2. Not-I
• 3. Not-(H and a1, a2, , an)
• 4. Not-H or not-a1, a2, , an
• 5. Not-H or not-a1 or not-a2 or or
• not-an
• (by De Morgans theorem)

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The Terrible Truth about Falsificationism
(continued)

• From a logical standpoint, no observation
  (whether experimental or in the field), can
  conclusively falsify a hypothesis. For it is
  always possible to salvage the hypothesis in the
  face of a failed prediction by denying an
  auxiliary assumption.

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More Nails in the Coffin of falsificationism

• Falsificationism is not only logically but also
  historically flawed.
• Faced with failed predictions scientists have
  historically denied auxiliary assumptions, e.g.,
  perturbations in the orbits of Uranus Mercury.
• Falsificationism is inconsistent with the
  practice of scientists training of young
  scientists
• Faced with failed predictions scientists
  typically deny and indeed are trained to deny
  auxiliary assumptions rather than the target
  hypothesis.

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Conclusion

• Neither inductivism nor falsificationism
  provides a satisfactory account of any scientific
  practice the scientific method of yore is a myth.

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Part II

• Differences in the methodology of classical
  experimental science and prototypical historical,
  natural science
• Is historical natural science methodologically
  inferior to experimental science?

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The structure of Classical Experimental Science

• Focus Is on a single (sometimes complex)
  hypothesis which typically has the form of a
  universal generalization (All Cs are Es).
• Central Research Activity Consists in repeatedly
  bringing about the test conditions specified by
  the hypothesis and controlling for extraneous
  conditions that might be responsible for false
  positives and false negatives.

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The Experimental Program vs. Solitary Experiment

• Failed predictions do not result in the
  rejection of hypotheses they are best
  interpreted as attempts to protect the hypothesis
  from false negatives.
• Successful predictions Are not followed by
  risky tests (in Poppers sense) they are best
  interpreted as attempts to protect the hypothesis
  from false positives.
• Acceptance/rejection of a hypothesis occurs only
  after a hypothesis is subjected to a series of
  experiments controlling for plausible auxiliary
  assumptions that could explain predictive
  successes and predictive failures.

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The structure of Prototypical Historical Science

• Focus Is on proliferating multiple, rival
  hypotheses to explain a puzzling body of traces
  of past events (data) encountered in field work.
• Central Research Activity Consists in searching
  for a smoking gun a trace(s) that sets apart
  one or more hypotheses as providing a better
  explanation for the body of traces thus far
  acquired than the others.

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A Case StudyThe Alvarez Hypothesis

• Two-pronged hypothesis 1) impact 2) extinction.
• Initially many different explanations for the
  end-Cretaceous mass extinction pandemic,
  evolutionary senescence, climate change,
  supernova, volcanism, and meteorite Impact.
• Discovery of an iridium anomaly (smoking gun)
  in K-T boundary sediments narrowed it down to two
  possibilities volcanism and meteorite impact.
  Discovery of extensive quantities of a rare form
  of shocked mineral subsequently cinched the case
  for impact over volcanism.

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A Case Study The Alvarez Hypothesis (cont)

• Paleontologists werent convinced They agreed
  that there had been a meteorite impact but many
  doubted that it caused the end-Cretaceous
  extinctions.
• The discovery of extensive pertinent fossil
  evidence (especially small organisms such as
  foraminifera and ammonites, and fern spores and
  angiosperm pollin) on either side of the K-T
  boundary was pivotal in changing their minds,
  providing the needed smoking gun for the second
  prong (mass extinction) of the hypothesis.

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Lessons from the Alvarez hypothesis The
evaluation of historical hyotheses is

• Not grounded in prediction
• Historical predictions are not risky in
  Poppers sense too many highly plausible
  extraneous conditions (e.g., iridium poor
  meteorite, geological processes of concentration
  and dispersal, unrepresentative samples of K-T
  boundary) capable of defeating them.
• Predictions are typically vague, e.g., Wards
  prediction about Cretaceous ammonites they
  serve more as roadmaps for looking for a smoking
  gun than predictions.

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The Evaluation of Historical Hypotheses (cont.)

• A hypothesis may be rejected on the basis of
  evidence that does not refute it, e.g., the
  contagion hypothesis for the end-Cretaceous
  extinctions.
• The acceptance of a hypothesis does not require a
  successful prediction, e.g., the iridium anomaly
  was not and could not have been predicted or
  retrodicted.

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The Evaluation of Historical Hypotheses(cont.)

• Grounded in explanatory power
• Hypotheses are accepted and rejected in virtue of
  their power to explain (vs. predict) puzzling
  bodies of traces discovered through field work.
• The Alvarez hypothesis explains an otherwise
  puzzling association (correlation) among traces
  better than any of its rivals. It is for this
  reason that it is viewed as confirmed and its
  rivals are no longer seriously entertained by
  scientists.

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Part III

• Common cause explanation and the search for a
  smoking gun

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Common Cause explanation

• Reichenbachs Principle of the Common Cause
  seemingly improbable associations (correlations
  or similarities) among traces are best explained
  by reference to a common cause.
• C
• Presupposes that the temporal structure of causal
  relations in our universe is such that most (not
  all) events form causal forks opening from past
  to future (leave many traces in the future).

E1 E2 E3 E4
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Common cause explanation (cont.)

• But is there any reason to believe the
• principle of the common cause is true?

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YES!The Asymmetry of Overdetermination

• A time asymmetry of causation
• Most local events structures overdetermine
  their past causes (because the latter typically
  leave extensive and diverse effects)and
  underdetermine their future effects (because they
  rarely constitute the total cause of an effect)
• Much easier to infer an ancient volcanic eruption
  than a near future volcanic eruption.

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The Asymmetry of Overdetermination (cont.)

• Physical source is controversial but it
  characterizes all wave (radiative asymmetry)and
  particle (2nd law of thermodynamics) phenomena
  above the quantum level an objective and
  pervasive physical feature of world.
• Physically (vs. logically or strictly
  metaphysically) grounds the Principle of the
  Common Cause and the methodology of historical
  natural science the Search for a smoking gun.

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An illustration The colors of dinosaurs

• Asym of OD Asserts that the present is filled
  with
• overdetermining traces of the past hence
• one can never completely rule out finding a
  smoking gun
• for any scientific hypothesis about the past.
  The
• methodology of historical field work is based
  upon
• this possibility.

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Conclusions

• Historical Scientists exploit the
  overdetermination of the past by the localized
  present by searching for a smoking gun to
  discriminate among competing hypotheses the
  asymmetry of overdetermination guarantees there
  are likely to be many such telling traces. The
  problem is recognizing them for what they
  represent.

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Conclusions

• 2. Experimental scientists try to circumvent the
  underdetermination of the future by the localized
  present by constantly testing for false positives
  and false negatives that might yield misleading
  confirmations or disconfirmations of their
  hypotheses the asymmetry of overdetermination
  guarantees that this is always a threat.
• There are no records of the future.

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Conclusions

• 3. The methodology of historical science is
  different from that of classical experimental
  science but it is not inferior each practice is
  designed to exploit the differing information
  that nature puts at its disposal.

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References

• Common cause explanation and the search for a
  smoking gun in Baker, V. (ed.), 125th
  Anniversary volume of the Geological Society of
  America (forthcoming).
• Prediction and Explanation in Historical
  Natural Science, British Journal of Philosophy
  of Science 62 (2011), 551-582.
• 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.
• Historical science, experimental science, and
  the scientific method, Geology 29, (2001), pp.
  987-990.