DEFEASIBLE REASONING.

Abstract

Our reasoning often leads to conclusions that we would reject if we had additional information. We need a general account of this 'defeasible' reasoning. Several accounts found in the literature give intuitively incorrect answers when applied to examples of correct defeasible reasoning in ordinary circumstances. An account that avoids these problems is developed as a formal system of sentential logic and an accompanying epistemic semantics. Called LDR, this logic is implemented in PROLOG.