the second is that it prevents anything else from being where it is; and the third is that, if others like it were added to it, a large volume and considerable magnitude would result. Undoubtedly, whatever is located in a region of space has these three properties. Yet the entity possessing these three properties must itself possess volume and magnitude. This is an intelligible feature common to all volumes. We have already demonstrated that this common concept cannot be an attribute of something else, but must be essential. Accordingly, space-occupying entities are identical in their essences and differ only in their attributes. The reasoning set out above therefore follows.

The second response is that, if the objection you have raised is sound, you cannot be certain that substances are identical in nature, since it might be said that substances