Abstract

This dissertation addresses the problem of trans-world identity in possible worlds semantics, and argues that essentialism does not provide a satisfactory solution to it. If one takes possible worlds semantics seriously as a viable elucidation of the logic of the metaphysical modalities, one must also take a realistic stance toward possible worlds. But then, contrary to Kripke, Plantinga, Van Inwagen, and others, there is a problem with trans-world identity; the real problem being, not the problem of identifying individuals across possible worlds, but rather the problem of the theoretical basis for these identifications. Possible worlds semantics presupposes a substantive theory of what constitutes the cross-world continuation or persistence of individuals. Standard formulations of these semantics nevertheless fail to articulate such a theory. Therefore cross-world identifications become inherently problematic. All available solutions to this problem either presuppose non-trivial essentialism or are incoherent. Non-trivial essentialism is the view that there are certain non-identity properties which a given individual has in every world in which it exists but which other possible individuals fail to have in some of the worlds in which they exist. ;But the question of the coherence of essentialism itself is intimately connected with one's views concerning the nature and existence of properties. Three Cantorian paradoxes are adduced, one against individuative essentialism, one against non-trivial essentialism, and one against properties in general. The paradoxes against properties in general and non-trivial essentialism can be avoided only if one eschews a Quine/Goodman view of property existence---the view that any extensionally well-defined class answers to a property---and makes some kind of distinction between natural and artificial properties. Nevertheless such an eschewal does not avoid the paradox of individuative essentialism. Thus essentialism cannot provide a completely adequate theory of trans-world individuation. For although it provides the necessary conditions for the identity of individuals across possible worlds, it does not allow us to identify these individuals on this basis alone. This conclusion precludes actualist solutions to the problem of the individuation of possibilia which quantify over individual essences.