On Restricting Rigidity

In this note I revive a lingering (albeit dormant) account of rigid designation from the pages of Mind with the aim of laying it to rest. Why let a sleeping dog lie when you can put it down? Andre Gallois (1986) has proposed an account of rigid designators that allegedly squares with Saul Kripke's (1980) characterisation of them as terms which designate the same object in all possible worlds, but on which, contra Kripke, identity sentences involving rigid designators may be merely contingently true. This suits Gallois, as he finds the notion of contingent identity coherent. Thus, the thrust of Gallois' thesis is that his account of rigidity is preferable to Kripke's because his accommodates a coherent metaphysical viewpoint, whereas Kripke's doesn't. Gallois has thwarted one unconvincing challenge (see Carter 1987; Gallois 1988) and his account, as yet, remains untainted. But not for long, I hope.' Let us assume, for the sake of argument, that the notion of contingent identity is coherent, that, in other words, it makes-or can make-sense to say that certain (possible) objects are identical in one world but distinct in another. What I shall argue here is that Gallois' account of rigidity would prevent us from expressing the contingent non-identity of objects; if so, this is a significant failing of the account, for, as will emerge, clearly Gallois is committed to the contingency of non-identity. Here's a brief outline of Gallois' position. He revives a familiar scenario involving the identity of ships. We are asked to consider a world W in which a ship designated "Mary" undergoes gradual plank replacement so that what eventually emerges is a ship made from a collection of planks, Cl, that has no members in common with the original collection of planks, C, that made up Mary. The resulting ship is christened "Alice" in W. We are then asked to consider a possible world WI which contains two ships: Mary,, made up of planks from C (arranged in the same way as when they constituted Mary in W) and Alice,, made up of planks from C1 (arranged in the same way as when they constituted Alice in W). Now, Gallois says: