 Langton and Lewis put forward their account as only an analysis of qualitative intrinsic properties, rather than intrinsic properties in general. Their account, however, arguably fails as an account of qualitative identity interior properties since, given numbers necessarily exist, it classifies being such that there is a number as intrinsic. Therefore, like the Lewis 1986a account, the Langton and Lewis account is arguably most charitably interpreted as an account of duplication preservation, or perhaps of qualitative metaphysical necessitation interiority.