Characterising rhetorical argumentation

The study of argumentation has undergone periods of decadence alternate with periods of renaissance. Currently, we are witnessing one of the latter, as proved by research flowering in many issues and aspects, both in Philosophy and in Artificial Intelligence. The work presented in this thesis is concerned in particular with “rhetorical argumentation”, which on the other hand has enjoyed consideration to a somewhat lesser extent. By rhetorical arguments we denote arguments which are both heavily based on the audience’s perception of the world, and concerned more with evaluative judgments than with establishing the truth or otherwise of a proposition. Rather than a logic focus on argumentative reasoning, or a pure computational linguistic focus on modelling discourse which happens to be argumentative, we place ourselves halfway and specifically focus on the characterisation of rhetorical argumentative discourse. Methodologically, we do this by explicitly drawing upon the philosophy of argument. The thesis proposes an all encompassing framework for the formalisation of rhetorical argumentation, inspired by a well established philosophical theory, the New Rhetoric. The thesis starts by giving a formal definition of rhetorical argument, and rhetorical reasoning. It proposes a model for a rhetorical dialogue game between two partners. It provides a characterisation of the game partners, in terms of their mental attitudes. The model is then applied to a particular task and domain, that is the provision of health education on nutritional issues. An ontological analysis of the knowledge required to perform the task is proposed, based on a psychological model of behavioural change. Finally, the thesis proposes an architecture integrating the various components, informed by the formal model defined. The work is admittedly biased towards the generation, rather than understanding, of argumentative discourse, and we see, and indeed we built, our formalisation to be comfortably used in a system for generating argumentative discourse based on planning. At the same time, we see our work as a contribution to typical pragmatic issues of providing a characterisation of what the speaker has to take into account when producing a “good” argument, and therefore what the hearer can ascribe to the speaker. The framework is well grounded on theoretical foundations, and indeed our proposal coherently integrates work in the philosophy of argument, in linguistics, in social psychology and in artificial intelligence.