 When forced to give up previous beliefs, the epistemic agent should give up beliefs that have as little explanatory power and overall informational value as possible. As an example of this, in the choice between giving up beliefs in natural laws and beliefs in single factual statements, beliefs in the natural laws, that have much higher explanatory power, should in general be retained. This was the basic idea behind Peter Gärdenfors’s proposal that contraction of beliefs should be ruled by a binary relation, epistemic entrenchment. (Gärdenfors 1988, Gärdenfors and Makinson 1988) To say of two elements \(p\) and \(q\) of the belief set that “\(q\) is more entrenched than \(p\)” means that \(q\) is more useful in inquiry or deliberation, or has more “epistemic value” than \(p\). In belief contraction, the beliefs with the lowest entrenchment should be the ones that are most readily given up.