Being Tolerant about Identity?

Abstract

Identity and identification are very important concepts in philosophy and logic. They are crucial for the analysis of quantification and for counting. According to some philosophers, many examples that are supposed to show that identity is contingent, in fact show that the notion of identity is relative. Leibniz's Principle is closely related to the principle of substitution. Many philosophers find ontic vagueness absurd. Moreover, vague identity due to ontic vagueness cannot exist, or so it is argued. The case of Theseus's ship (TS) is like that of the sorites paradoxes but this time for identity. Vague predicates seem to be tolerant in the sense that a small enough difference in the relevant properties of two objects cannot make a difference in the applicability of the predicate. Finally, the chapter examines contingent identity by making use of sortal variables with a constraint on their interpretation. Keywords: contingent identity; relative identity; Theseus's ship (TS); tolerant logic; vague identity