Incommensurability, Proportionality, and Rational Legal Decision-Making

Courts frequently engage in the weighing of competing values; perhaps most obviously, such balancing constitutes an integral aspect of proportionality analysis in many states’ constitutional law. However, such balancing raises a difficult theoretical question: What does it mean that one value “outweighs” another in any particular case? If the values at issue are incommensurable — as they often will be — such balancing may appear to break down. As Justice Scalia has stated, balancing in the presence of incommensurable values “is more like judging whether a particular line is longer than a particular rock is heavy.” It may appear that if a judge is asked in a particular case to decide, for example, whether a state interest is sufficiently strong to justify the limitation of a constitutional right, he will be forced to a) either abandon the notion of a genuine plurality of values, or b) make an arbitrary decision.This article argues that neither of these options need be accepted and that rational choice is indeed possible in the presence of incommensurable values. Specifically, it contends that the Nash bargaining solution provides a means, at least in certain circumstances, of rationally understanding and undertaking the weighing of distinct and mutually irreducible values which adjudication frequently requires. The Nash framework can both elucidate proportionality analysis by providing a social choice-based framework for understanding the structure of proportionality analysis and also justify proportionality analysis by demonstrating that the weighing of competing values is not necessarily mere judicial hand-waving.