Noting specific inadequacies with truth-conditional approaches, Ishikawa develops a dynamic theory of reference incorporating features of Discourse Representation Theory, File Change Semantics and Situation Semantics, and also deals with non-monotonic belief revision. He argues that the task of natural language semantics is to describe meaning in terms of the psychological relation of language to our cognition of external reality. In his approach, a linguistic expression's meaning is its potential to change the information state of a cognitive agent. Reference is not understood as a link to a real individual external to an agent, but as the agent's act to link a character in a linguistic frame of individuation to characters in other (linguistic or nonlinguistic) frames. As the target of inquiry, the distinction between referential and attributive uses of definite descriptions is analyzed through the construction of conversation scenarios. In addition, Ishikawa extends his theory to an analysis of belief and attitude reports. Application of the theory to cleft and pseudocleft constructions is also outlined. Presented in a very accessible style, Ishikawa's theory will be of interest to scholars in cognitive science/artificial intelligence and philosophy as well as linguistics.