Constraint and Freedom in the Common Law

The purpose of this paper is to advance our formal understanding of the common law, especially the nature of the reasoning involved, but also its point, or justification. As so often in discussions of the modern common law, I will concentrate on the doctrine of precedent, according to which decisions by earlier courts constrain decisions by later courts, while still allowing these later courts a degree of freedom to respond in creative ways to fresh circumstances. It is this balance between constraint and freedom that forms the primary focus of the paper. In limiting my attention to the constraining role of precedent, however, I do not mean to downplay the complementary role played by precedent cases in analogical reasoning, or to deny that, in practice, these two roles can be elaborately intertwined. Although the coherence theories of precedential constraint associated with writers such as Ronald Dworkin, as well as the nihilistic theories associated with the American legal realists, both have a good deal of interest, I will set them aside in this paper to begin with the more familiar position that constraint in the common law is based on rules—that a court faced with a particular case either invokes a previous common law rule or articulates a new one to justify its decision, and that it is this rule that constrains the decisions of future courts.1 This general idea, which might be referred to as the rule model of precedential constraint, can be developed in two ways, depending on the nature of the rules involved. Some writers feel that common law rules are best seen as defeasible, or prima facie, leading to the defeasible rule model of constraint. I have a good deal of sympathy with this view, have explored it in my own work, and agree that precedential constraint is defeasible. But there are other ways of capturing this overall pattern of defeasibility than by assuming from the outset that the underlying rules must themselves be defeasible. To illustrate, I will take as my starting point the position that common law rules are strict, or