Supposition-Based Logic for Automated Nonmontonic Reasoning

We present a first-order logical system based on a standard first-order language which is enriched with new predicate symbols — supposition predicates. The logic is standard. The interesting non-standard features of a nonmonotonic logic are captured by considering whether a given consequence depends on the special predicates. A supposition theory contains formulas of the original language and special axioms governing the behaviour of the suppositions. Our system, when applied to suppositions theories, has many of the desired features of a nonmonotonic logic. We also discuss proof procedures issues.