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  • 1. University of Notre DameProgram in the History and Philosophy of ScienceDepartment of PhilosophyThe Early History of‘Chance’ in Evolution&HPS4, Athens, GreeceCharles H. Pencecharles@charlespence.net
  • 2. A Talk in Three Acts• Act I: The “standard” historical narrative of chance inevolution
  • 3. A Talk in Three Acts• Act I: The “standard” historical narrative of chance inevolution• Act II: A problem for the standard narrative: Pearson andWeldon
  • 4. A Talk in Three Acts• Act I: The “standard” historical narrative of chance inevolution• Act II: A problem for the standard narrative: Pearson andWeldon• Act III: A speculative philosophical conclusion
  • 5. The “Standard History”• Two questions:
  • 6. The “Standard History”• Two questions:1. When did evolutionbecome a statisticaltheory?
  • 7. The “Standard History”• Two questions:1. When did evolutionbecome a statisticaltheory?2. When did evolutionbecome a theory of“genuinely chancy”processes?
  • 8. Some Preliminaries: Darwin
  • 9. Some Preliminaries: DarwinOrigin (1859), p. 106
  • 10. Question 1: Francis Galton
  • 11. Question 1: Francis GaltonThe principle on which the action of the apparatusdepends is, that a number of small and independentaccidents befall each shot in its career. In rare cases,a long run of luck continues to favour the course of aparticular shot towards either outside place, but inthe large majority of instances the number ofaccidents that cause Deviation to the right, balance ina greater or less degree those that cause Deviation tothe left. […] This illustrates and explains whymediocrity is so common.Galton, Natural Inheritance (1889), pp. 64–65
  • 12. Question 2: Sewall WrightFrom Provine, Sewall Wright and Evolutionary Biology
  • 13. Question 2: Sewall Wright
  • 14. A Problematic: Pearson & Weldon
  • 15. Traditional Questions: Pearson
  • 16. Traditional Questions: PearsonIn our ignorance we ought to consider beforeexperience that nature may consist of all routines, allanomalies, or a mixture of the two in any proportionwhatever, and that all such are equiprobable....Pearson, Grammar of Science, 1st ed. (1892), p. 172
  • 17. Traditional Questions: WeldonAll experience, which we are obliged to deal withstatistically, is experience of results which dependupon a great number of complicated conditions, somany and so difficult to observe that we cannot tell inany given case what their effect will be.Weldon, “Inheritance in Animals and Plants” (1906), p. 97
  • 18. Pearson & Weldon on Chance• Pearson and Weldon theorize extensively about their useof chance
  • 19. Pearson & Weldon on Chance• Pearson and Weldon theorize extensively about their useof chance• This theorizing is not captured by the two “traditional”questions
  • 20. Pearson & Weldon on Chance• Pearson and Weldon theorize extensively about their useof chance• This theorizing is not captured by the two “traditional”questions• It provides us the historical impetus we need to build anew framework for understanding chance
  • 21. Pearson & Weldon on Chance• Pearson and Weldon theorize extensively about their useof chance• This theorizing is not captured by the two “traditional”questions• It provides us the historical impetus we need to build anew framework for understanding chanceAuthors personal copy‘‘Describing our whole experience’’: The statistical philosophies ofW. F. R. Weldon and Karl PearsonCharles H. PenceUniversity of Notre Dame, Program in History and Philosophy of Science, 453 Geddes Hall, Notre Dame, IN 46556, USAa r t i c l e i n f oKeywords:BiometryMendelismKarl PearsonPositivisma b s t r a c tThere are two motivations commonly ascribed to historical actors for taking up statistics: to reduce com-plicated data to a mean value (e.g., Quetelet), and to take account of diversity (e.g., Galton). Differentmotivations will, it is assumed, lead to different methodological decisions in the practice of the statisticalsciences. Karl Pearson and W. F. R. Weldon are generally seen as following directly in Galton’s footsteps. Iargue for two related theses in light of this standard interpretation, based on a reading of several sourcesStudies in History and Philosophy of Biological and Biomedical Sciences 42 (2011) 475–485Contents lists available at SciVerse ScienceDirectStudies in History and Philosophy of Biological andBiomedical Sciencesjournal homepage: www.elsevier.com/locate/shpsc
  • 22. Pearson & Weldon on Chance1. What was the content of Pearson’s and Weldon’sphilosophical work on chance?
  • 23. Pearson & Weldon on Chance1. What was the content of Pearson’s and Weldon’sphilosophical work on chance?2. What is the right way to understand their philosophicalproject?
  • 24. Pearson and Biometry[The last step of the scientific method is] thediscovery by aid of the disciplined imagination of abrief statement or formula, which in a few wordsresumes the whole range of facts. Such a formula…istermed a scientific law. The object served by thediscovery of such laws is the economy of thought.Pearson, Grammar of Science, 1st ed. (1892), p. 93
  • 25. Pearson and Biometry[The lack of progress in biology is] largely owing to acertain prevalence of almost metaphysical speculationas to the causes of heredity, which have usurped theplace of that careful collection and elaborateexperiment by which alone sufficient data might havebeen accumulated, with a view to ultimatelynarrowing and specialising the circumstances underwhich correlation was measured.Pearson, “Mathematical Contributions to the Theory of Evolution.III. Regression, Heredity, and Panmixia” (1896), p. 255
  • 26. Weldon on StatisticsIf we want to make a statement about the stature ofEnglishmen, we must find a way of describing ourwhole experience; we must find some simple way ofdescribing our whole experience, so that we caneasily remember and communicate to others howmany men of any given height we find among athousand Englishmen. We must give up the attemptto replace our experiences by a simple average valueand try to describe the whole series of results ourobservation has yielded.Weldon, “Inheritance in Animals and Plants” (1906), p. 94
  • 27. Weldon on CauseProf. Weldon declared, with some expressions of reluctance andregret – due, as he was good enough to say, from an old pupilto the teacher whom he is about to denounce and demolish –that to attempt to say which of two or more correlated growthsis the cause of survival is unreasonable, and that when Isuggested, even as a matter for consideration, that a certaingerm-slaying quality in phagocytes accompanying a pigmentedskin, rather than the pigment itself in the skin, is the cause ofthe survival of dark-skinned people in malarial regions, I was“absolutely illogical.” “It is,” said Prof. Weldon, “impossiblelogically to separate these two correlated phenomena. Thecoloured skin is as much a cause of the survival of the dark manas is the germ-destroying property of his blood.”E. Ray Lankester, “Are Specific CharactersUseful? [letter]” Nature 54:1394 (1896), p. 245
  • 28. Pearson vs. WeldonOn the second point [causation], surelyProf. Lankester is entirely in the right? It is notsufficient to show that there is a correlation betweena certain frontal ratio and death-rate in order toassert that the frontal ratio is a cause of death-rate.Very probably it may be, but the definition is notlogically complete, or at any rate a definition of causehas been adopted which does not appear of muchutility to science.Pearson, “The Utility of Specific Characters [letter]”Nature 54:1403 (1896), pp. 460–461
  • 29. Weldon’s Crabbery
  • 30. Pearson & Weldon on ChancePearson:• Positivist role of science for the economy of thought• Statistics as a tool for simplification of data• Causation as precise mathematical law (think Newton)Weldon:• Science as the maximally complete description of nature• Statistics as a tool to capture all causal influences• Causation = correlation (and experiments sharpen ourcorrelations)
  • 31. What’s the Driving Question?
  • 32. What’s the Driving Question?What is the relationship between statistical scientific theoriesand the processes those theories intend to describe?
  • 33. What’s the Driving Question?What is the relationship between statistical scientific theoriesand the processes those theories intend to describe?• Pearson: acausal, anti-realist view of biological theories
  • 34. What’s the Driving Question?What is the relationship between statistical scientific theoriesand the processes those theories intend to describe?• Pearson: acausal, anti-realist view of biological theories• Weldon: statistical theories as causal descriptions of theworld
  • 35. Speculative Philosophical CodaThe “causalist/statisticalist debate” in the philosophy ofbiology:
  • 36. Speculative Philosophical CodaThe “causalist/statisticalist debate” in the philosophy ofbiology:• Causalist: Biological theories describe causal processes ofnatural selection and genetic drift
  • 37. Speculative Philosophical CodaThe “causalist/statisticalist debate” in the philosophy ofbiology:• Causalist: Biological theories describe causal processes ofnatural selection and genetic drift• Statisticalist: Biological theories are merely statisticalsummaries of genuinely causal individual-level events
  • 38. Speculative Philosophical CodaThe “causalist/statisticalist debate” in the philosophy ofbiology:• Causalist: Biological theories describe causal processes ofnatural selection and genetic drift (Hodge, Beatty, Finsen, Millstein,Stephens, Ramsey, Abrams, Otsuka, Turner, Allen, Lloyd)• Statisticalist: Biological theories are merely statisticalsummaries of genuinely causal individual-level events(Walsh, Matthen, Ariew, Lewens, Ernst, Krimbas, Brunnander)
  • 39. Speculative Philosophical CodaPearson and Weldon’s question: What is the relationshipbetween statistical scientific theories and the processes thosetheories intend to describe?
  • 40. Speculative Philosophical CodaPearson and Weldon’s question: What is the relationshipbetween statistical scientific theories and the processes thosetheories intend to describe?Causalist/statisticalist question: The same?
  • 41. Speculative Philosophical CodaPearson and Weldon’s question: What is the relationshipbetween statistical scientific theories and the processes thosetheories intend to describe?Causalist/statisticalist question: The same?Odd case: historical case responds better to contemporaryquestions than to historical questions?
  • 42. ..ευχαριστώ!charles@charlespence.net