Argumentation in AI and law

This chapter introduces AI & Law approaches to legal argumentation, showing how such approaches provide formal models that succeed in capturing key aspects of legal reasoning. The chapter is organised as follows. Sections 2, 3, and 4 introduce the motivations and developments of research on argumentation within AI & Law. Section 2 looks into the notion of formal inference, and shows how deduction-based approaches fail to account for important aspects of legal reasoning. Section 3 introduces the idea of defeasibility, and argues that an adequate model of legal reasoning should take it into account. Section 4 presents some AI & Law models of argumentation. The remaining sections are dedicated to introducing a formal account of argumentation based on AI & Law research. Section 5 defines and exemplifies the notion of an argument. Section 6 discusses conflicts between arguments and their representation in argument graphs. Section 7 defines methods for assessing the status of arguments and evaluating their conclusions, and Section 8 summarises the steps from premises to dialectically supported conclusions