Hardness of case-based decisions: a formal theory

Stare decisis is a fundamental principle of case-based reasoning. Yet its application varies in complexity and depends, in particular, on whether relevant past decisions agree, or exist at all. The contribution of this paper is a formal treatment of types of the hardness of case-based decisions. The typology of hardness is defined in terms of the arguments for and against the issue to be decided, and their kind of validity (conclusive, presumptive, coherent, incoherent). We apply the typology of hardness to Berman and Hafner's research on the dynamics of case-based reasoning and show formally how the hardness of decisions varies with time.