 Another way in which plural quantification and second-order quantification come apart emerges in modal contexts. It is often a contingent matter whether an object falls under a concept. Although I am wearing shoes, I might not have done so. So there is a concept \(F\) under which I fall but might not have fallen. In contrast, it seems that being one of some objects is never contingent. Consider the people \(aa\) who are all and only the people currently wearing shoes. Then not only am I one of these people, but this seems to hold of necessity (assuming the existence of the relevant objects). Removing me from this plurality of people would just result in a different plurality. For the plurality \(aa\) to be the plurality it is, it must include precisely the objects that it in fact includes. So in any world in which the objects \(aa\) exist at all, I must be one of them. True, I might not have been wearing shoes. But even so I would have been one of \(aa\), only then \(aa\) would not have been all and only the people wearing shoes. Plural names and variables thus seem to be rigid in a way that is analogous to the familiar rigidity of singular names and variables: in any world in which a plural term denotes at all, it denotes the same objects. In particular, it is widely believed that pluralities are subject to the following two principles: