 Prior’s next two axioms for n-statability express principle S above. The first captures the left-to-right direction that, intuitively, expresses the supervenience of propositions on their subjects: a statement \(\varphi\) is n-statable only if the things referred to in \(\varphi\) are necessary beings. Prior could in fact express that the object signified by an individual constant \(\sfa\) is necessary in the usual fashion as \(\Box\exists \sfx\,\sfx=\sfa\) but, given \(\Box\textbf{Def}_Q\), this unpacks rather cumbersomely to \(\rS \exists \sfx\,\sfx=\sfa \land ◼\exists \sfx\,\sfx=\sfa\). However, as we will see, in the context of Q this is equivalent simply to \(\rS \exists \sfx\,\sfx=\sfa.\) For convenience, Prior shortens this to \(\rS \sfa\); more  generally:[76]