Rigid designator is an expression that refers to the same entity in every possible world. According to Kripke (1972), this is the case with proper names, i.e. names of individuals. The definite description the president of the US may refer to different persons in different worlds, but the denotation of the proper name Richard Nixon is the same person in every possible world. Kripke accounts for the relation between a name and its bearer by a causal theory of reference: the first use of a name for an individual determines its designation independent of its meaning properties (initial baptism). Kripke (1972) made the claim that natural kind terms (i.e. names of biological sorts, natural or mineral substances) are also rigid designators.
- Gamut, L.T.F. 1991. Logic, language, and meaning, Univ. of Chicago Press, Chicago.
- Kripke, S.A. 1972. Naming and Necessity, D.Davidson and G.Harman, eds. Semantics of Natural Language, Reidel:Dordrecht.