The place of instrumental reasoning in law

Most people think of law as an instrument that can help us achieve human purposes that can themselves be adequately specified without reference to law or legal ideas. But a number of scholars, associated in various ways with the natural law tradition in jurisprudence, have argued that we should understand law non-instrumentally, in the sense that its role is to constitute rightful relations between people, where the rightfulness of these relations cannot be specified apart from the legal ideas, institutions, principles, and rules that constitute them. On this view, the law cannot be instrumental because its purpose cannot be understood independently of the way it achieves that purpose. In this paper, I argue that these two views are compatible to the following extent. Even if the point of the legal order as a whole is to constitute a state of affairs that is rightful in a sense that cannot be characterised apart from legal ideas, instrumental reasoning about the causal effectiveness of particular laws in achieving particular purposes is not precluded, indeed is essential, provided those purposes are themselves understood as contributions to the constitution of just relations between people rather than as contributions to the achievement of some independently defined good.