 The supposition that Adam and Noah differ in their essential properties in this way, although sufficient to block the generation of this example of a role-switching world, does not by itself imply that each of Adam and Noah has an individual essence: a set of essential properties whose possession is (not only necessary but also) sufficient for being Adam or Noah. Suppose that Adam has, as one of his essential properties, living in the Garden of Eden, whereas Noah essentially lacks this property. This will block the possibility of Noah’s playing the Adam role, although it does not, by itself, imply that nothing other than Adam could play that role. However, when we reflect on the potential generality of the argument, it appears that, if we are to block all cases of role-switching concerning actual individuals, we must suppose that every actual individual has some essential property (or set of essential properties) that every other actual individual essentially lacks. For example, to block all cases of role-switching concerning Adam and other actual individuals, there must be some component of ‘the Adam role’ that is not only essential to being Adam, but also cannot be played, in any possible world, by any actual individual other than Adam.