A Three-dimensional Ontology of Customs

Understanding legal customs is a matter of balancing an external factor against an internal one: the former a practice, the latter a belief about the normative character of that practice. In this paper, I try to show how this circular relationship can describe the way customs emerge and develop. To this end I use some conceptual tools developed in contemporary social ontology and analytic metaphysics. I conclude that (a) legal institutions are governed by a three-dimensional ontology and that (b) when we turn custom, this three-dimensional structure will turn out to be markedly different from that that can be identified in positive law. In order to unpack this argument I begin, in Section 2, by showing how the ontology of legal institutions is three-dimensional, meaning that it can be analyzed into three distinct, though intertwined, layers. Then, in Section 3, I analyze the three-dimensionality of positive law by describing the relations of existential dependence, supervenience, and grounding that hold among the three layers. I proceed in Section 4 by applying this analysis to customary law: this will make it possible to see what distinguishes customary law from positive law and to conjecture two phenomena specific to customs, the aforementioned “sedimentation” and “rooting.” Finally, in Section 5, I will conclude by exemplifying sedimentation and rooting through an imagined example of a customary legal institution.