 The most critical problem in applying circumscription is that of deciding on what predicates to minimize (there is, in addition, a further technical question about which predicates to treat as fixed and which as variable in extension). Most often what is done is to introduce a family of abnormality predicates \(ab_1, ab_2\), etc. A default rule then can be written in the form: \(\forall x((F(x) \amp \neg ab_i (x) ) \rightarrow G(x))\), where “\(\rightarrow\)” is the ordinary material conditional of classical logic. To derive the consequences of a theory, all of the abnormality predicates are simultaneously minimized. This simple approach fails to satisfy the principle of Specificity, since each default is given its own, independent abnormality predicate, and each is therefore treated with the same priority. It is possible to add special rules for the prioritizing of circumscription, but these are, of necessity, ad hoc and exogenous, rather than a natural result of the definition of the consequence relation.