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Irrelevant Conjunction and the Ratio Measure or Historical Skepticism

Pitts, J. Brian (2011) Irrelevant Conjunction and the Ratio Measure or Historical Skepticism. [Preprint]

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    It is widely believed that one should not become more confident that _all swans are white and all lions are brave_ simply by observing white swans. Irrelevant conjunction or "tacking" of a theory onto another is often thought problematic for Bayesianism, especially given the ratio measure of confirmation considered here. It is recalled that the irrelevant conjunct is not confirmed at all. Using the ratio measure, the irrelevant conjunction is confirmed to the same degree as the relevant conjunct, which, it is argued, is ideal: the irrelevant conjunct is irrelevant. Because the past's really having been as it now appears to have been is an irrelevant conjunct, present evidence confirms theories about past events only insofar as irrelevant conjunctions are confirmed. Hence the ideal of not confirming irrelevant conjunctions would imply that historical claims are not confirmed. Confirmation measures partially realizing that ideal make the confirmation of historical claims by present evidence depend strongly on the (presumably subjective) degree of belief in the irrelevant conjunct. The unusually good behavior of the ratio measure has a bearing on the problem of measure sensitivity. For non-statistical hypotheses, Bayes' theorem yields a fractional linear transformation in the prior probability, not a linear rescaling, so even the ratio measure arguably does not aptly measure confirmation in such cases.

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    Item Type: Preprint
    Additional Information: Forthcoming in _Synthese_
    Keywords: irrelevant conjunction, tacking, Bayesianism, confirmation measure, induction
    Subjects: General Issues > Confirmation/Induction
    Specific Sciences > Earth Sciences
    General Issues > History of Philosophy of Science
    General Issues > Logical Positivism/Logical Empiricism
    General Issues > Operationalism/Instrumentalism
    General Issues > Realism/Anti-realism
    General Issues > Science and Religion
    General Issues > Science vs. Pseudoscience
    Depositing User: Dr. Dr. J. Brian Pitts
    Date Deposited: 25 May 2011 12:03
    Last Modified: 08 Jun 2011 09:27
    Item ID: 8616

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