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PY226: Philosophy of Science

PY226: Philosophy of Science. [F]alsificationists like myself much prefer an attempt to solve an interesting problem by a bold conjecture, even (and especially) if it soon turns out to be false, to any recital of a sequence of irrelevant truisms. Karl Popper. Review:.

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PY226: Philosophy of Science

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  1. PY226: Philosophy of Science [F]alsificationists like myself much prefer an attempt to solve an interesting problem by a bold conjecture, even (and especially) if it soon turns out to be false, to any recital of a sequence of irrelevant truisms. Karl Popper

  2. Review: • What is falsification? Why does Popper hold that falsification is a better model for scientific method than inductivism? • According to falsification, how does science proceed? • What is the demarcation problem? • If falsification is correct, how would it solve the demarcation problem?

  3. Today’s topics: Context of Discovery vs. Context of Justification Duhem-Quine Problem Problems for falsification Karl Popper (1902-1994)

  4. Context of Discovery vs. Context of Justification • According to inductivism, what is the relation between observation and theory? • Popper: “[T]he act of conceiving or inventing a theory seems to me neither to call for logical analysis nor to be susceptible to it. … [I]t is irrelevant to the logical analysis of scientific knowledge” (cited on p. 75) • Why does Popper think the act of inventing a theory is irrelevant to the logical analysis of scientific knowledge?

  5. “An experiment … can never condemn an isolated hypothesis but only a whole theoretical group” (Duhem cited on p. 77) The logic of refutation: Let T = theory, p = prediction 1) If T then p 2) ~ p 3) Therefore, ~ T Duhem-Quine Problem

  6. How are predictions ‘deduced’ from a theory? Pierre Duhem (1861-1916) and Willard V.O. Quine (1908-2000) The logic of refutation (Duhem-Quine): If (T and A) then p ~ p Therefore ~ (T and A) ~ (T and A) = ~ T or ~ A Therefore, ~ T or ~ A Duhem-Quine problem

  7. Duhem-Quine Problem • What does the conclusion ~ T or ~ A allow us to do in the logic of refutation? • Do we have to reject the theory immediately when we have a disconfirmation?

  8. Duhem-Quine Problem • “Physical science is a system that must be taken as a whole; it is an organism in which one part cannot be made to function except when the parts that are most remote from it are called into play, some more so than others, but all to some degree” (Duhem cited on 79). • Duhem’s view is called wholism. Wholism concerns justification, the way our beliefs are justified.

  9. Duhem-Quine: Popper’s response • Popper’s response (80): • Conflict between high-level theory and disconfirming observation leads to further tests. The experimental procedure for the test are agreed to by the relevant scientists. If the conflict between theory and observation cannot be resolved, then the theory has to be rejected. From the perspective of the practice of science, the refutation is conclusive

  10. Popper’s response: • What has Popper conceded? • Nonetheless, “it is still the case that if the scientific community accepts the truth of a statement reporting the observation of a negative instance of some theory …it is logically inconsistent for the community to believe the generalization as well. On the other hand, there is nothing inconsistent in accepting the truth of a positive instance of the same generalization and at the same time believing the generalization to be false” (80-81). Why?

  11. Problems for falsification • Some parts of science appear not to be falsifiable: • 1) existential claims: e.g. there are black holes • 2) some scientific laws appear not to be falsifiable because they are constitutive of the very practice of science

  12. Problems for falsification • Falsification is itself not falsifiable • Popper responds by saying that falsification is a logical principle and not itself part of science (makes no bold conjectures) • It can be treated like other formal principles, such as Occam’s razor

  13. Problems for falsification • Falsification cannot account for our expectations about the future: • Since we can’t say that theories that have withstood challenges are true, why should we continue to believe them? (This question calls for more than a pragmatic response)

  14. Problems for falsification • Popper’s solution: the concept of corroboration (a theory is corroborated if it made a bold conjecture … that is not falsified) • Corroborated theories are ones we have least reason to believe false. So it is rational for us to continue to believe in them.

  15. Problems for falsification • Falsification cannot completely dispense with induction (induction through the backdoor) • (1) From Duhem-Quine problem, we know that predictions are generated only in conjunction with background assumptions. • Which of the background assumptions do we reject? What does that judgment depend on? • (2) What about the very idea of a ‘novel’ prediction?

  16. Problems for falsification • Popper is more radical than Hume: How is it possible that scientists are not to use induction at all? • Suppose you are a scientist. Your results show that a particular theory T has been successful in the past, predicting the location of comets say, wouldn’t it be rational for you to keep using the theory? • The examples of Neptune and Mecury

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