Paraconsistent Logics and Identity - a Pragmatic Approach MSc

This thesis investigates what role paraconsistency can play in dealing with traditionally intractable problems concerning identity and change. More specifically, we consider three logics that all commit to a Leibnizian account of identity, but that provide distinct solutions to a version of the sorites paradox related to the Ship of Theseus. It is shown how the first of these logics solves the problem by taking an approach that embraces inconsistency, rendering invalid some familiar principles, while the second takes a more consistent approach, satisfying these familiar principles, but is not able to capture some core elements of paraconsistency. The final logic uses positive features of both approaches to provide a radically different account of the nature of change. This logic is particularly interesting in that it is a non-monotonic logic inspired by pragmatic considerations regarding vagueness. The viability of each approach is assessed in part according to their treatment of the paradox, and in part according to five rules of inference that we argue any account of identity should allow.