 In circumscription (McCarthy 1982; McCarthy 1986; Lifschitz 1988), one or more predicates of the language are selected for minimization (there is, in addition, a further technical question of which predicates to treat as fixed and which to treat as variable). The nonmonotonic consequences of a theory \(T\) then consist of all the formulas that are true in every model of \(T\) that minimizes the extensions of the selected predicates. One model \(M\) of \(T\) is preferred to another, \(M'\), if and only if, for each designated predicate \(F\), the extension of \(F\) in \(M\) is a subset of the extension of \(F\) in \(M'\), and, for some such predicate, the extension in \(M\) is a proper subset of the extension in \(M'\).