 On Lewis’s ‘extreme realist’ account of possible worlds, it looks as if, for Clover to exist in another possible world as well as the actual world would be for her to be a part of such a world: Clover would somehow have to exist as a (concrete) part of two worlds, ‘in the same way that a shared hand might be a common part of two Siamese twins’ (Lewis 1986, 198). But this is problematic. Clover actually has four legs, but could have had three legs. Should we infer that Clover is a part of some world at which she has only three legs? If so, then how many legs does Clover have: four (since she actually has four legs), or seven (since she has four in our world and three in the alternative world)? Worse still, we appear to be ascribing contradictory properties to Clover: she has four legs, and yet has no more than three.