On the general metaphysics of haecceities, see Adams (1979, 1981), Cover and O’Leary-Hawthorne (1997), Cowling (2015), Lewis (1986), Swinburne (1995), and Rosenkrantz (1993). On epistemological and metaphysical issues about haecceities—e.g., whether individuals can be acquainted with the haecceities of other individuals—see Rosenkrantz (1993). On haecceities and the identity of indiscernibles, see Robinson (2000). On haecceities of mathematical entities and their role in mathematical structuralism, see Shapiro (2006: 139).