 Here an independently plausible conception of conversational exchange comes to her aid. The utterances of speakers and the interpretive activity of listeners is profoundly and pervasively shaped by the current values of a small number of basic situating parameters. These parameters have fairly determinate values at each stage in a well-run conversation; a wide variety of conversational proprieties and improprieties turn on their current values at any given stage; the values change from utterance to utterance in response to publicly discernible events in a manner governed by simple principles of conversational dynamics, so that careful and well-situated participants have a fighting chance of keeping track of their changing values. Participants need that fighting chance, since fluent unconstrained conversational exchange resulting in full understanding by each of what all the others are saying requires the participants to possess more or less accurate, more or less thoroughgoing mutual knowledge of the values of the parameters at each and every point in the exchange.