This chapter introduces the idea of a plural legal category, namely, a legal category that is deeply heterogeneous and, nonetheless, legally meaningful. More specifically, it proposes structural pluralism as an alternative to the prevailing assumption of structural monism. It argues that a wholesale category should not be a category for deciding; pigeonholing a case within its ambit is not enough to justify any concrete decision. At times, however, holding on to such a category can still be useful because some heterogeneous legal categories can function as categories of thinking. Thus, a wholesale legal category is theoretically important if its subcategories raise questions that invoke similar normative concerns or imply some similarity in the means that inform their pertinent answers. This chapter offers an account of plural legal categories and demonstrates its promise regarding fiduciary law, which it analyzes as a classic example of a plural legal category. It also discusses autonomy-based pluralism in fiduciary law and shows how, despite the significant differences between various fiduciary types, their structural similarities could facilitate learning and cross-fertilization and thereby justify holding such diverse categories as money managers, parents, and sovereigns under the unified umbrella of fiduciary law. Furthermore, since many fiduciary types enhance autonomy, the pertinent subsets of fiduciary law dealing with the facilitation of various forms of money management and division of labor can and should be critically examined against this important function of liberal law.