 A third reaction is to accept bare identities—or, at least, to accept that individuals (including actual individuals) may have qualitative duplicates in other possible worlds, and that transworld identities may involve what have been called ‘haecceitistic’ differences. (See Adams 1979; Mackie 2006, Chs 2–3; Lewis 1986, Ch. 4, Section 4; also the separate entry on Haecceitism.)