 Even if we suppose that all actual individuals are distinguished from one another by such ‘distinctive’ essential properties, this still does not, strictly speaking, imply that they have individual essences. For example, it does not rule out the existence of a possible world that is exactly like the actual world except that, in this possible world, the Adam role is played, not by Adam, but by some merely possible individual (distinct from all actual individuals). However, if we find intolerable the idea that there are such possible worlds—worlds that, like the role-switching world, differ from the actual world only in the identities of some of the individuals that they contain—then, it seems, we must suppose that individuals like Adam (and Noah and you) have (non-trivial) individual essences, where an individual essence of Adam is (by definition) some property (or set of properties) that is both essential to being Adam and also such that it is not possessed, in any possible world, by any individual other than Adam—i.e., an essential property (or set of properties) that guarantees that its possessor is Adam and no one else.