Nonmonotonicity and the Scope of Reasoning

Autocircumscription was introduced in part to modularize circumscription into a consistency part and a default part. We have found, to our surprise, that putting the two parts together can actually provide a stronger default mechanism than unmodularized circumscription. This depends in part on an assessment of the `scope` of reasoning, to determine the appropriateness of employing a default axiom.