How should judges decide the cases presented to them? In our system the answer is, “according to law,” as opposed to the judges’ preferred outcomes. But for at least a century, skeptics have cast doubt on whether adjudication under law is possible. Judge Richard Posner, now retired from the U.S. Court of Appeals for the Seventh Circuit, has, for example, argued that the indeterminacy of legal argument and the influence of judges’ predispositions show that it is not. Judge Posner thus recommends that judges give up on the rule of law in contested cases and instead candidly base their decisions on what they take to be in the best interests of society. Is there a convincing response to Judge Posner’s critique? H.L.A. Hart famously sought to de...