 Given philosophers typically use ‘intrinsic’ to express some notion of interiority, there are several reasons to think that the notion of interiority they typically express is that of identity interiority. First, identity interiority is more fundamental, or simpler, than the other notions of interiority, and philosophers are often interested in employing more fundamental notions than less fundamental notions. Second, the intrinsic properties of a thing should be the properties that thing has “in itself”, rather than merely the properties that are metaphysically necessitated, or nomically necessitated, or metaphysically explained, by the properties the thing has “in itself”. But this suggests that the intrinsic properties should be the identity interior properties, rather than the metaphysical necessitation interior properties, or the nomic necessitation interior properties, or the weak grounding interior properties. Finally, while the identity interiority of necessarily coextensive properties can intuitively differ, this is not true for at least some of the other notions of interiority, such as metaphysical necessitation interiority and nomic necessitation interiority. Since it is a widespread intuition that necessarily coextensive properties can differ in whether they are intrinsic, this suggests these other notions of interiority aren’t what philosophers typically express by ‘intrinsic’. (This last reason also provides a further reason to think that duplication preservation isn’t the notion of intrinsicality philosophers typically employ, since it also does not differ among necessarily equivalent properties.)