Carter on Contingent Identity and Rigid Designation

Abstract

In a paper entitled 'Rigid Designation and the Contingency of Identity' I stated a condition for a designator to designate rigidly, and made the following claims about it.1 First, the condition in question, referred to as RDC, is extensionally adequate. No designator conforming to it intuitively fails to be rigid, and no designator failing to conform to it intuitively qualifies as rigid. Second, an identity sentence incorporating only designators satisfying RDC could be contingently true. Hence, if proper names need only satisfy RDC to qualify as rigid designators an identity sentence containing only proper names could be contingently true. Apart from making these claims on behalf of RDC I described a candidate example of a contingent identity which I will call the case of the ships. The case of the ships features the ships Mary, Alice, Mary1, and Alice1. Mary and Alice are located in possible world W, and Mary1 and Alice1 are located in world W1. In W Mary is originally constructed from the members of a plank collection C, and Alice eventuates from Mary by a gradual but complete identity-preserving replacement of the members of C with the members of the non-overlapping plank collection C1. In W1 Mary1 is originally constituted from the members of C, and Alice1 is originally constituted from the members of C1. I contended that there is something to be said for taking Mary to be identical to Mary1 in W, and something to be said for taking Alice to be identical with Alice1 in W. Mary and Mary1 are originally identically constituted, and Alice and Alice1 are identically constituted from much of their careers. However, if Mary is identical with Mary1 in W, and Alice is identical with Alice1 in W then, by the transitivity of identity, Mary1 is identical with Alice1 in W. Hence, Mary1 is identical with Alice1 in W, and Mary1 is non-identical with Alice1 in W1. So Mary1 is contingently identical with Alice1. In 'Contingent Identity and Rigid Designation' William R. Carter challenges the extensional adequacy of RDC.2 In addition, Carter disputes that the case of the ships can be plausibly thought of as a contingent identity on the following grounds. Carter contends that the most satisfactory solution to the problem posed by the case of the ships implies no contingent identity. In addition, he constructs a dilemma for anyone who takes the case of the ships to be an example of a contingent identity. According to Carter the case of the ships raises certain transworld identity questions, and on any resolution of them, turns out not to be a case of a contingent identity. I will begin this reply by considering Carter's criticism of RDC. In 'Rigid Designation and the Contingency of Identity' RDC was stated as follows: