 However, it is not clear how to formalize this condition in first order logic. In essence, we would need to modify (\(\ref{eq:boygirl1}\)) so that \(z\) is not in the scope of \(x\), and hence it does not depend on it; however, we would still want \(z\) to depend on \(y\) and \(y\) on \(x\). As just discussed, however, such a dependency pattern is not realizable in first-order logic. We can sidestep the issue by resorting to higher-order quantification: indeed, one can see that the expression 