 Circumscription does have the capacity of representing the existence of undercutting defeaters. Suppose that satisfying predicate \(F\) provides a prima facie reason for supposing something to be a \(G\), and suppose that we use the abnormality predicate \(ab_1\) in representing this default rule. We can state that the predicate \(H\) provides an undercutting defeater to this inference by simply adding the rule: \(\forall x (H(x) \rightarrow ab_1 (x))\), stating that all \(H\)s are abnormal in respect number 1.