Speech acts that support other speech acts

Theories of discourse structure and existing discourse structure annotation schemes (e.g. Mann and Thompson, 1988; Sanders, 1997; Asher and Lascarides, 2003; Webber et al., 2019) often make a distinction between propositional, subject-matter, or semantic coherence relations on the one hand, and speech-act-level, presentational, or pragmatic relations, on the other. While there have been several convincing attempts to circumscribe the space of all possible propositional relations and to subdivide it into theoretically motivated subcategories (Sanders et al., 1992; Kehler, 2002), to date there is no comparable comprehensive taxonomy for speech-act-level relations. This paper develops a fragment of a such taxonomy, which describes what we call support relations—relations that connect two speech acts iff one of them fails to achieve its goal and the other helps achieve that same goal, as for instance, in Evidence relations, where one speech act makes the proposition asserted in the other more believable. We provide conceptual motivation for the proposed categories grounded in isights from sociolinguistic, psychological, and philosophical studies of human communication and illustrate the categories with examples from naturally occurring discourse, some of which do not fiteasily into any existing classifications.