NAMING AND IDENTITY IN EPISTEMIC LOGIC .2. A FIRST-ORDER LOGIC FOR NAMING

Modal epistemic logics for many agents sometimes ignore or simplify th e distinction between the agents themselves, and the names these agent s use when reasoning about each other. We consider problems motivated by practical computer science applications, and show that the simplest theories of naming are often inadequate. The issues we raise are rela ted to some well-known philosophical concerns, such as indexical descr iptions, de re knowledge, and the problem of referring to nonexistent objects. However, our emphasis is on epistemic logic as a descriptive tool for distributed systems and artificial intelligence applications, which leads to some nonstandard solutions. The main technical result of this paper is a first-order modal logic, specified both axiomatical ly and semantically (by a variant of possible-worlds semantics), that is expressive enough to cope with all the difficulties we discuss.