 Despite these virtues, the grammatical approach faces a difficult question: why think that the structures we find in language reflect the metaphysical structures of the world? For instance, it may simply be a historical accident that our language contains individuating and non-individuating predicates. Likewise, it may be a historical accident that there are active and passive verbs in our language. Of course, this type of objection, when pushed to its limits, leads to one of the more difficult philosophical questions, namely how can we be sure that the structures of our representations are in any way related to what some might call the basic metaphysical structures and to what others might call the things in themselves? But one might hold out hope that some justification for a categorial scheme could be given that did not rest entirely on the unjustified assertion of some deep correspondence between linguistic and metaphysical structures.