Discourse Structure and the Structure of Context - Multiple Choices

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throughout. In such a situation KUtt is, at least as far as n is concerned,
immutable. The situation is different, when utterance times are
determined by utterances which cover only a small part of the
discourse (e.. the utterance of an indexical expression on its own, or of
the sentence in which the expression occurs). In that case KUtt changes
beteen utterances belonging to the same discourse and thus shows a
kind of dynamics. 29
2. In English and also in many other languages there is a range of
indexical temporal expressions, whose interpretation depends on the
29 Cases in which the utterance time is taken to be that of the entire discourse
present a certain difficulty, especially when we assume that they involve anchoring of
n to this discourse time. It is quite common for the discourse participants to take the
utterahnce time as that of the entire discourse without having any clear idea, durin
the early part of their conversation for how long it will og on; and, indeed, this may
be genuinely undetermined when the conversation begins. In this case the period to
which n is anchored is not yet fixed and it might be wondered how anchoring would
be possible in such cases.
As a matter of fact I do take this to be a serious problem. As soon as the discourse
begins, its time is accessible to the participants - as the time of the discourse that has
just started - and the fact that the full extent of his time is still indeterminate desn't
prevent it from serving as an anchor. (More ought to be said about exactly what this
implies for the notion of anchoring we have been using, but this would lead too far
afield.)
I believe, however, that the indeterminacy of the time of the entire discourse has an
important implication. Because in so many cases the full extent of the global
utterance time cannot be determined until the discourse has actually come to a
conclusion, it is part of interpretations which make use of this default strategy to take
the utterance time to be inherently indeterminate, with the attendant constraint that
the result of interpretation should not depend on what the utterance time will turn
out to be in the end. Extrapolating from this we arrive at the constraint that
intrpretation should be independent of which subinterval of the duration of the entire
discourse is assumed as utterance time. it is easily seen that this constraint restricts
what can be said to precisely the three possibilites listed in (3): either ev lis in the
future of the entire discourse, in which the appropriate tense is a future tense, or ev
has ended before the discourse started, in which a past tense is appropriate; or ev
spans the entire duration of the entire discourse, in which present tense is
appropriate, with the additional proviso that ev is the kind of eventuality that is
interpreted as including tloc, rather than being included in it. (It is easy to verify that
when and only when we presupppose that the eventuality described by a sentence S
satisfies one of these three possibilities that it becomes immaterial which subinterval
of the discourse duration is chosen in interpreting S.) A discourss whose sentences
satisfy this presuppopsition is semantically robust in that the truth conditions which
interpetation assigns to them are indpendent of what - within the duration of the
discourse as a whole - is taken as the relevant utterance time. This is an alternative
way of explaining why the tripartite division of (3) should hold.