Miller, MichaelPerlis, DonThe tie between linguistic entities (e.g., words) and their meanings (e.g., objects in the world) is one that a reasoning agent had better know about and be able to alter when occasion demands. This has a number of important commonsense uses. The formal point, though, is that a new treatment is called for so that rational behavior via a logic can measure up to the constraint that it be able to change usage, employ new words, change meanings of old words, and so on. Here we do not offer a new logic per se; rather we borrow an existing one (step logic) and apply it to the specific issue of language change. (Also cross-referenced as UMIACS-TR-94-36)en-USTechnical Report