This chapter provides a possibly unwelcome defense of the significance of legal taxonomy. It may be unwelcome because it starts from a very different jurisprudential premise than the one shared by most of the scholars interested in taxonomy who tend to be positivists. The jurisprudential underpinnings of this chapter are of course realist; and realism, at least in the account of this book, is antithetical to legal positivism. It is argued that the profound realist critique of legal positivism is quite damaging to the positivist rationale of legal taxonomy. But legal realism does not look down on taxonomy. Rather, there are good (read: legal realist) reasons for considering legal taxonomy significant. Identifying these reasons is important not only to show that realists can and should care about taxonomy, but also because it points to some prescriptions about the taxonomic enterprise that are quite distinct from the way taxonomy is envisioned from a positivist (or doctrinalist) perspective.