Apples and Oranges: The Commensurability Debate in Legal Scholarship

Much recent debate on the economic analysis of law has focused on "commensurability" - the proposition that all options can be compared by reference to a single metric - such as utility or money. Commensurabilists argue not only that we can, but that we should, compare alternatives and make choices based on commensuration. Indeed, classical price theory holds that only choices made on the basis of commensurability are economically rational. Proponents of incommensurability argue that certain alternatives can not or perhaps should not be ranked according to some single metric or lowest common denominator because no single metric can capture the rich diversity of values. Indeed, to even attempt such a utilitarian calculus is to diminish our humanity. Unfortunately, this has largely been a debate without dialogue. Both proponents and opponents of commensurability tend to assert that their position must be true because the presuppositions on which their opposition's position is based are self-evidently false. Consequently, the debate resembles an "is not", "is too" playground argument. Rather than making logical arguments derived from a set of first principles, both sides of the arguments rely primarily on empirical examples that supposedly disprove the tenets of their opponent. The proponents of both sides of the argument do agree that the truth of their own side can be established by pointing out the flaws of the other side. The debate is owned, but only temporarily, by whoever makes the last argument. Both sides are, therefore, ultimately equally unconvincing. We have before us a classic Kantian antinomy based on apagogic reasoning. Both sides assume that something crucial hangs on the question of commensurability - specifically that one's position on commensurability has a necessary relationship to one's position on the economic analysis of law. That is, if one agrees that commensuration is possible or appropriate,then one should - or must - also accept a utilitarian, cost-benefit analysis of legal regimes. A rejection of utilitarianism, therefore, seems to require a rejection of commensuration. Consequently, both sides assume that if they lose the debate on commensurability then they must also give up their most cherished legal and political ideals. It is the thesis of this Article that absolutely nothing pends on this debate precisely because the debate itself is inept. In contrast, speculative theory does not assume that one side of the debate is the opposite or simple negative of the other. Rather, the speculative tradition has its origin in Kant's insight that certain propositions that seem to be logically inconsistent with each other, may necessarily require each other in the sense that each is a true but incomplete and inadequate description of the world. Hegel famously expressed Kant's paradox as the doctrine of the identity of identity and difference. Interestingly for the purposes of this Article, he developed this through the specific example of the dialectical relationship between quantity (commensurability) and quality (incommensurability). In the twentieth century, psychoanalyst Jacques Lacan goes further and interprets this paradox as the very heart of human subjectivity - a subjectivity formed by an essential non-relationship between the masculine (commensurability) and the feminine (incommensurability). In this Article, I trace the speculative relationship between commensuration and incommensuration from Kant, through Hegel and to Lacan. I argue that, although logically incompatible, every choice necessarily reflects a moment of both commensuration (the recognition of quantitative difference) and incommensuration (the recognition of qualitative difference). Choice and exchange form the place at which commensuration and incommensuration meet. A speculative theorist, therefore, agrees with the utilitarian that commensuration is both possible and a necessary aspect of choice. Nevertheless, she disagrees with the utilitarian's assertion that rational choice is determined by commensuration. Commensurability along a single metric is never a reason to make a choice or engage in an exchange because rationality is defined as the very capacity for spontaneous, free - and, therefore incommensurate - action. Commensurable values merely represent a limitation on the choices one can make in the sense that one is limited to choosing what one can afford. Incommensurable or qualitative values always drive choice.