Presuppositions in Spoken Discourse

Chapter 2
describing defeasible inference rules, i.e. rules that generate inferences that may
later be revised or abandoned because of additional knowledge.
Asher & Lascarides (1998b) treat presupposition resolution as an integrated
part of the task of building a discourse representation. They believe that the
original binding theory cannot properly deal with all examples of presupposition
because it lacks a richer representation of discourse structure which place a part in
some examples. They consider one of the biggest problems with the binding theory
to be its treatment of accommodation. Accommodated information is not related
to the discourse in any principled way, it is merely added. That there is a need for
accommodated information to be integrated into the discourse representation is
often noted in binding theory literature (e.g. van der Sandt, 1992, Geurts 1999), but
how and to what degree this integration should proceed is not discussed in any
detail, if at all. Asher & Lascarides’ (1998b) proposal eliminates the need for pure
accommodation by instead treating all cases that would be accommodated in the
original binding theory as binding to a rhetorical relationship. This is one of the
important ways in which their treatment of presupposition differs from the original
binding theory. They also believe that they can explain more easily why some uses
of accommodated presuppositions result in infelicitous discourses, an explanatory
ability that they see as a definite advantage over van der Sandt’s (1992) account
which would treat these examples as normal, permissible adjustments of the input
context by accommodation.
In their account, binding and accommodation are both treated by the same
method ⎯ by binding via a rhetorical relationship to the rest of the discourse
representation at some accessible attachment site. Because they also consider nonidentity
relationships such as the relationship between inferred information, such as
bridging NPs, to a be related by binding to other objects in the discourse, basically
all information is resolved by the same method. At first glance this seems to blur
the distinction between assertional meaning and presuppositional meaning.
However, when the resolution process begins, the presupposed information and
the asserted information are separated. In resolution, presupposed information is
treated differently than asserted information in two important ways.
First, presupposed information is generally related to the discourse by the
rhetorical relationship of Background, where the presupposition is considered to be
background information to the proposition to which it attaches. Alternatively the
presupposition can be related to another proposition by Defeasible-Consequence or
Def-Con, where the proposition to which the presupposition is bound is considered
to be a defeasible consequence of the presupposition. The majority of triggers are
rhetorically related via Background or Defeasibile-Con and this is meant to capture the
intuition that presupposed information is backgrounded or taken for granted. Some
triggers however, particularly particles, are treated differently, associated with a
particular rhetorical relationship almost exclusively. Asher and Lascarides mention
too in particular, where the presupposition it triggers is always rhetorically related via
the Parallel relationship to another proposition. The induced presupposition of
because is always related via the relation of Explanation to an earlier proposition in
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