The 'Expiscation' of Legal Principles

This chapter deals with one way in which courts are said to rely on precedent: they sometimes look at a string of previously decided cases and seek to ‘extract’ or ‘induce’ or ‘expiscate’—the language used to describe the move varies—a principle that underlies them. The standard view among legal theorists is that courts in such instances are drawing an inference that somehow relies on (a) the fact that those previous cases were authoritatively decided in a certain way to (b) a more general conclusion about a principle that ‘unites’ them. This chapter argues that the standard view is wrong. The ‘expiscatory’ move involves no distinctive inference from past cases to general principle; it does not amount to a specific way of relying on precedents as sources of content-independent practical reasons. But the chapter begins by introducing a theoretical framework that conceptualizes judicial decisions in terms of the relevant questions courts can be said to face, and by then clarifying the practices of both following precedent and extending it by analogy. Once we are clear about those two ways of relying on precedents as sources of content-independent practical reasons, the ‘expiscatory’ move becomes easier to understand—and to demystify.