 The moral that Chisholm (1967) drew from his argument was scepticism about transworld identity, based partly on scepticism about whether the non-trivial individual essences that would block the generation of role-switching worlds are available. Others would go further, and conclude that such puzzles provide not only a reason for rejecting transworld identity, but also a reason for adopting counterpart theory. (Note, though, that Lewis’s reasons for adopting counterpart theory appear to be largely independent of such puzzles (cf. Lewis 1986, Ch. 4).)