Interpretation, argumentation, and the determinacy of law

The paper models legal interpretation though argumentation and provides a logical analysis of interpretive arguments, their conflicts and resulting indeterminacies in interpretation. First a general pattern is introduced for representing interpretive arguments. Such arguments are modelled as defeasible inferences, which can be challenged by counterarguments. Arguments and counterarguments participate in larger argumentative interactions, where defeated arguments may be reinstated when their defeaters are in their turn defeated. The idea is then developed of an interpretive argumentation basis, i.e., the set of interpretive canons and premises that can be used to build or attack interpretive arguments. It is shown what claims are possibly (defensibly) or necessarily (justifiably) supported by the arguments constructible from a given interpretive basis. Finally, it is established under what conditions such arguments provide single outcomes, or rather support alternative interpretive solutions, and consequently lead to propositions of law whose truth value is undetermined.