  Lewis finds a replacement for Ways in a principle of  recombination whereby “patching together parts of  different possible worlds yields another possible world” (1986, 87–88). The principle has two aspects. The first is the principle  that “anything can coexist with anything”. For “if  there could be a dragon, and there could be a unicorn,” Lewis  writes, “but there couldn't be a dragon and a unicorn side by  side, that would be ... a failure of plenitude” (ibid.,  88). Given that individuals are worldbound, however, the principle is expressed more rigorously (and more generally) in terms of  other-worldly duplicates: 