 Kraus, Lehmann, and Magidor proved that, for every preferential consequence relation \(\dproves\) that is probabilistically  admissible,[5]  there is a unique rational consequence relation \(\dproves^*\) that minimally extends it (that is, that the intersection of all the rational consequence relations extending \(\dproves\) is also a rational consequence relation). This relation, \(\dproves^*\), is called the rational closure of \(\dproves\). To find the rational closure of a preferential relation, one can perform the following operation on a preferential structure that supports that relation: assign to each model in the structure the smallest number possible, respecting the preference relation. Judea Pearl also proposed the very same idea under the name 1-entailment or System \(Z\) (Pearl 1990).