 Consider, for concreteness, the special case of classical first-order languages. Let the ground language \(L\) be one such, and let its interpretations be models of some sentences \(T\). Say that an interpretation \(M^{+}\) of \(L^{+}\) is an expansion of an interpretation \(M\) of \(L\) iff \(M\) and \(M^{+}\) have the same domain and they assign the same semantic values to the non-logical constants in \(L\). Furthermore, let us say that