Questions of identity1

This article is about the interpretation of quantifiers in epistemic contexts, and the closely related notion of what it means for two objects in different possible worlds to be identical. I will give arguments for several claims. The first claim is that the definition of identity between objects across epistemically possible worlds as being given by the identity of those objects themselves leads to empirical as well as conceptual problems. Recent examples of such a view on identity are the theory of questions of Groenendijk and Stokhof (1997) and the semantics for quantified modal logic of Groenendijk et al. (1996). Secondly, I will argue that these problems can be circumvented by taking trans-world identity to be a notion that is external to the possible worlds themselves (by some sort of counterpart theory, or by a set of individual concepts). This raises the old question what exactly this notion of identity is. I will argue by way of examples that there is no single notion of trans-world identity, but that the way we speak about objects depends on contextual factors. In this paper, I will concentrate mostly on the analysis of questions and of ‘knowing who,’ but the points raised here are also relevant to issues related to de re knowledge and belief and the interaction of epistemic ‘might’ and quantifiers. I will address these and other issues in a more extended version of this paper.