An Integrated View on Rules and Principles

In the law, it is generally acknowledged that there are intuitive differences between reasoning with rules and reasoning with principles. For instance, a rule seems to lead directly to its conclusion if its condition is satisfied, while a principle seems to lead merely to a reason for its conclusion. However, the implications of these intuitive differences for the logical status of rules and principles remain controversial.A radical opinion has been put forward by Dworkin (1978). The intuitive differences led him to argue for a strict logical distinction between rules and principles. Ever since, there has been a controversy whether the intuitive differences between rules and principles require a strict logical distinction between the two. For instance, Soeteman (1991) disagrees with Dworkin's opinion, and argues that rules and principles cannot be strictly distinguished, and do not have a different logical structure.In this paper, we claim that the differences between rules and principles are merely a matter of degree. We give an integrated view on rules and principles in which rules and principles have the same logical structure, but different behavior in reasoning. In this view, both rules and principles are considered to consist of a condition and a conclusion. The observed differences between rules and principles are, in our view, the result of different types of relations that they have with other rules and principles. In the integrated view, typical rules and typical principles are the extremes of a spectrum.We support our claim by giving an explicit formalization of our integrated view using the recently developed formal tools provided by Reason-Based Logic. As an application of our view on rules and principles, we give three ways of reconstructing reasoning by analogy.