Reasoning with Reasons in
Case-Based Comparisons

Kevin D. Ashley and Bruce M. McLaren
University of Pittsburgh, Pittsburgh, Pennsylvania 15260

Abstract. In this work, we are interested in how rational decision makers reason
with and about reasons in a domain, practical ethics, where they appear to reason
about reasons symbolically in terms of both abstract moral principles and case
comparisons. The challenge for reasoners, human and artificial, is to use abstract
knowledge of reasons and principles to inform decisions about the salience of
similarities and differences among cases while still accounting for a case's or
problems specific contextual circumstances. TRUTH-TELLER is a program we
have developed and tested that compares pairs of cases presenting ethical
dilemmas about whether to tell the truth. The programs methods for reasoning
about reasons help it to make context sensitive assessments of the salience of
similarities and differences.

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