 Degree of essentialness. Given a valid argument \((\Gamma,\phi)\) and a premise \(\gamma\in\Gamma\), the degree of essentialness of \(\gamma\), written \(E(\gamma)\), is \(1/|S_\gamma|\), where \(|S_\gamma|\) is the cardinality of the smallest essential premise set that contains \(\gamma\). If \(\gamma\) does not belong to any minimal essential premise set, then the degree of essentialness of \(\gamma\) is 0.