In light of disagreement about which entities play the role of possible worlds, no characterization of haecceitism that makes substantive assumptions about the nature of possible worlds will prove acceptable to all ersatzists. (On ersatzism, see Lewis (1986: 136–142), Divers (2002: 167–292), and Sider (2002).) Despite this, competing ersatzist views can employ their own distinctive resources to provide formulations of haecceitism. For instance, if possible worlds are identified with maximal consistent sets of propositions, haecceitism can be taken as the claim that there are distinct maximal consistent sets of propositions that include the same qualitative propositions but different non-qualitative propositions. For other versions of ersatzism, alternative strategies for formulating haecceitism that appeal to properties, sets, or other entities are available, but none that deploy contentious metaphysical commitments will have a plausible claim to being a canonical expression of haecceitism.