Categorizing Justifications in Legal Argument

In this paper I discuss the various justifications that can be given for components of a legal argument. First a number of different types of argument are described. These are used in legal reasoning, but cannot be satisfactorily reduced to deductive arguments. While deductive arguments have been fruitfully analysed in the literature, these other forms of arguments, and the ways in which they can be challenged are relatively unexplored from any kind of formal perspective. I suggest a way of describing these forms of argument in an extended version of Toulmin’s well known argument schema. I conclude by arguing that progress in a computational understanding of legal reasoning requires that we address these non-deductive argument forms.