# Logic & Philosophy of Science

**Carl Wagner**

Department of Mathematics, University of Tennessee

## “Uncertain Old Evidence and
Probabilistic New Explanation”

Richard Jeffrey has devised a probability revision method,
called reparation, that increases the probability of hypothesis H
when it is discovered that H implies previously known evidence E.
The speaker has generalized Jeffrey's method to the case of
uncertain old evidence and probabilistic new explanation, based on
the so-called "uniformity principle," which, in one of its several
avatars, dictates that explanation-based revisions should preserve
certain Bayes factors. A plausible alternative principle dicates that
observation- and explanation-based revisions should commute.
One formulation of the latter principle is equivalent to the uniformity
principle, but another is not. In this talk, we will survey the
mathematical properties of these competing revision principles, and
raise the question of whether one has a superior claim to ground a
generalization of reparation, or if each might be applicable to a
separate class of uncertain old evidence problems.

## Friday, March 24, 2000

SSPB 1208, 3 pm

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