Scorekeeping in a language game

At any stage in a well-run conversation, a certain amount is presupposed. The parties to the conversation take it for granted; or at least they purport to, whether sincerely or just “for the sake of the argument”. Presuppositions can be created or destroyed in the course of a conversation. This change is rule-governed, at least up to a point. The presuppositions at time r’ depend, in a way about which at least some general principles can be laid down, on the presuppositions at an earlier time r and on the course of the conversation (and nearby events) between r and r’. Some things that might be said require suitable presuppositions. They are acceptable if the required presuppositions are present; not otherwise. ‘me king of France is bald” requires the presupposition that France has one king, and one only; “Even George Lakoff could win” requires the presupposition that George is not a leading candidate; and so on. We need not ask just what sort of unacceptability results when a required presupposition is lacking. Some say falsehood, some say lack of truth value, some just say that it’s the kind of unacceptability that results when a required presupposition is 1acking;and some say it might vary from case to case. Be that as it may, it’s not as easy as you might think to say something that will be unacceptable for lack of required presuppositions. Say something that requires a missing presupposition, and straightway that presupposition springs into existence, making what you said acceptable after all. (Or at least, that is what happens if your conversational partners tacitly acquiesce if no one says “But France has three kings! ” or ‘Vhadda ya mean, ‘even George’? “) That is why it is peculiar to say, out of the blue, “All Fred’s children are asleep, and Fred has children.” The first part requires and thereby creates a presupposition that Fred has children; so the second part adds nothing to what is already presupposed when it is said; so the second part has no conversational point. It would not have been peculiar to say instead “Fred has children, and all Fred’s children are asleep.”