Discourse dynamics, pragmatics, and indefinites

Everyone agrees that conversations take place in a context. This is not to merely point out that conversations occur at a time and a place, or that there are particular speakers and hearers, though this is all of course true. Conversations take place against a background of mutually recognized facts: facts about the beliefs and presumptions of the participants, facts about the information conveyed thus far, facts about what’s under discussion, and so on. Although there is some disagreement as to the exact nature of conversational contexts, it is generally agreed that they record these sorts of facts. As Stalnaker (1978) and Lewis (1979) first pointed out, the context both affects and is affected by the utterances in a conversation. Consider a conversation in which I ask (1) and another one in which I ask (2):