ABSTRACT
This chapter presents the notion of a "possible world." In an argument against description theories of proper names, Saul Kripke appealed to the notion of a "possible world" or universe alternative. Kripke argues that when one uses the name "Nixon" to refer to a person in this world and then starts describing hypothetical scenarios or alternative possible worlds, continuing to use the name, one is talking about the same person. Subsequent direct reference (DR) theories of names have been built on Marcus' and Kripke's work. Bertrand Russell used the four puzzles and his spot-check argument to attack the view that ordinary proper names are Millian names, in favor of the Description Theory. The causal–historical view's key notion is that of the passing on of reference from one person to another. This view sharply opposed a long-held Descriptivist Theory of natural-kind terms, which associated each such term with a descriptive stereotype.
