 The main representation theorem of Kraus, Lehmann, and Magidor concerns the system P in terms of preferential models. Below we repeat the rules of the system, except that here axioms come in argument form (the entailment symbol “\(\pipsim\)” is not part of the object language), and inference rules in meta-argument form. The rules in the systems they consider are not thought of as validity preserving. They are rather taken to be closure conditions: any reasonable nonnomotonic inference relation \(\pipsim \) is such that when it includes the premises (sometimes, though, the premises are exclusion conditions, see RMon, DRat and NRat below), then it includes the conclusion, too. Kraus, Lehmann and Magidor’s representation results then state that an inference relations \(\pipsim \) is reasonable in this syntactically specified sense just in case it can be defined by a model with certain properties.