 As seen, Kripke objects to the necessitation of open formulas. Indeed, if open formulas are understood as universally closed, \(\Diamond Fx\rightarrow(\exists x)\Diamond Fx\) is to be read as \((\forall x)(\Diamond Fx\rightarrow(\exists x)\Diamond Fx)\) and Prior’s proof will not go through. On the other hand, the open formula \(\Diamond Fx\rightarrow(\exists x)\Diamond Fx\) is already ‘problematic’ insofar as it does not hold in a model with two worlds \(G\) and \(H\), where the domain of \(G\) is \(\{a\}\) and the domain of \(H\) is \(\{a, b\}\), and where \(Fa\) is false in both \(G\) and \(H\), but \(Fb\) is true in \(H\). In this model \(\Diamond Fx\) is true but \((\exists x)\Diamond Fx\) is false in \(G\). In this counter-model \(\Diamond Fx\) is made true in \(G\) by the individual \(b\) that is not in the domain of \(G\). 