A reduction-graph model of ratio decidendi

This paper proposes a model of ration decidendi as a justification structure consisting of a series of reasoning steps, some of which relate abstract predicates to other abstract predicates and some of which relate abstract predicates to specific facts. This model satisfies four adequacy criteria for ratio decidendi identified from the jurisprudential literature. In particular, the model shows how the theory under which a case is decided controls its precedential effect. By contrast, a purely case-based model of ratio fails to account for the dependency of precedential effect on the theory of decision.