Defeat Among Arguments: A System of Defeasible Inference

This paper presents a system of non-monotonic reasoning with defeasible rules. The advantage of such a system is that many multiple extension problems can be solved without additional explicit knowledge; ordering competing extensions can be done in a natural and defensible way, via syntactic considerations. The objectives closely resemble Poole's objectives. But the logic is different from Poole's. The most important difference is that this system allows the kind of chaining that many other non-monotonic systems allow. Also, the form in which the inference system is presented is quite unusual. It mimics an established system of inductive logic, and it treats defeat in the way of the epistemologist-philosophers. The contributions are both of content and of form: (content) the kinds of defeat that are considered, and (form) the way in which defeat is treated in the rules of inference