Abstract
Elliott Sober argues that the statistical slogan “Absence of evidence is not evidence of absence” cannot be taken literally: it must be interpreted charitably as claiming that the absence of evidence is (typically) not very much evidence of absence. I offer an alternative interpretation, on which the slogan claims that absence of evidence is (typically) not objective evidence of absence. I sketch a definition of objective evidence, founded in the notion of an epistemically objective likelihood, and I show that in Sober’s paradigm case, the slogan can, on this understanding, be sustained.
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Notes
This in virtue of the principle of rationality dictating that in normal circumstances, conditional subjective probabilities should be set equal to corresponding physical probabilities (Lewis 1980).
All such probabilities should be regarded as implicitly conditioned on the dig’s having been completed as planned, for the reasons given in Sect. 1.
Here I assume for simplicity’s sake that the hypothesis is independent of the auxiliaries, so that P(a i |h) = P(a i ). This is in fact a rather tendentious assumption (Strevens 2001, note 7); however, its dubious status does no harm to my argument here.
Equally, you might note that it is a mathematical truth that \(P(\neg e|h) = 1 - P(e|h)\); one of these two likelihoods cannot, then, be more objective than the other.
This is not quite Sober’s assumption; his concerns the probability of finding some fossil intermediate or other, whereas mine concerns the probability of finding a fossil representative of some particular intermediate form. The difference is significant for the justification of the assumption; see the end of this section.
References
Lewis, D. (1980). A subjectivist’s guide to objective chance. In R. C. Jeffrey (Ed.), Studies in inductive logic and probability (Vol. 2). Berkeley, CA: University of California Press.
Sober, E. (2008). Evidence and evolution: The logic behind the science. Cambridge: Cambridge University Press.
Sober, E. (2009) Absence of evidence and evidence of absence: Evidential transitivity in connection with fossils, fishing, fine-tuning, and firing squads. Philosophical Studies. doi:10.1007/s11098-008-9315-0.
Strevens, M. (2001). The Bayesian treatment of auxiliary hypotheses. British Journal for the Philosophy of Science, 52, 515–538.
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Strevens, M. Objective evidence and absence: comment on Sober. Philos Stud 143, 91–100 (2009). https://doi.org/10.1007/s11098-008-9312-3
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DOI: https://doi.org/10.1007/s11098-008-9312-3