Cheng Book Roundtable: Predicting, Explaining and Guiding (A Response to Professor Ku)

I am glad that there is very little distance between me and Professor Ku. We both agree that legal theory does not have to be predictive to be successful. In this regard, Professor Ku finds my theory compelling “as a matter of politics and policy.”

Professor Ku implies, however, that may have set too low a bar in attempting to present an approach to international law that guides rather than controls. He contrasts my approach to positivisim, which he says “claims to control,” and rationalism, which he says “claims to predict.”

I wonder if Professor Ku assigns too much to the goal of positivism. In 1999, in the American Journal of International Law, Bruno Simma wrote:

Relying on a positivist conception of law does not necessarily imply subscribing to the view that there is only one correct answer to any legal problem. Rather, it means that we do not give up the claim to normativity and the prescriptive force of law. In many cases, law does provide guidance regarding what to do or not to do.

If one accepts Judge Simma’s summary of modern positivism, then positivism, like my theory, aims to “guide.” The relevant question is then not whether the goal of guiding is too modest, but whether each theory does a good job guiding.

I also wonder if Professor Ku’s description of rationalism’s goal is shared by the scholars he identifies as leading that field. Eric Posner and Jack Goldsmith explicitly state in The Limits of International Law:

We do not make fine grained predictions. . . . Our goal is, rather, to give a simple but plausible account for the various features of international law . . . in terms of something other than a state’s propensity to comply with international law.

In other words, rationalist theories and my theory try to explain how the international legal system functions or fails. The reader will have to decide for him or herself whether the highly-contextual accounts of international incidents in my book provide useful explanations of decisions and outcomes.