It may be argued that the modal structural account does not require an isomorphism between (applied) mathematical structures and those describing the material situation. The account only requires an isomorphism between two standard models of the overall theory T′, which links the mathematical theory T and the description S of the material domain. In reply, note that this only moves the difficulty one level up. In order for T′ to extend the applied mathematical theory T and to provide a link between T and the material situation, a model of T′ will have to be, in particular, a model of both T and S. Thus, if the modal structuralist's synthetic determination claim is satisfied, an isomorphism between two models of T′ will determine an isomorphism between the models of S and those of T. In this way, an isomorphism between structures describing the material situation and those arising from applied mathematics is still required.