This dissertation examines the early modern Japanese legal practice of incorporating narratives drawn from the cosmological and anthropological theories of the archipelago’s varying religious traditions. From the formation of Tokugawa law in 1603 until Matsudaira Sadanobu’s Kansei reforms at the close of the eighteenth century, lawmakers and their critics relied on cosmological and anthropological narratives to explain and justify their attempts to make Tokugawa law and, particularly in moments of crisis, to reframe it. While the use of religious narratives occurred consistently over a two-hundred-year period, legal arguments based on cosmology were not a pervasive feature of Tokugawa law. Instead, lawmakers generally used these narratives in a specific context— to support or corrode the authority of the constitutional laws that framed the Tokugawa legal order. Evaluating Tokugawa legal cosmology offers new perspective on a conundrum found in Tokugawa law; the cosmological narratives that appear in Tokugawa law varied widely over the course of the Tokugawa period, even as the substantive laws that they supported remained remarkably consistent. Tokugawa law, and particularly the Tokugawa constitutional laws, presented an appropriate forum to contest the political authority of the Tokugawa government. Legal cosmology served as an ideological battleground precisely because there was no “cosmological consensus.” Here, interested actors constantly contested political authority in Tokugawa law in furtherance of personal or group interests. In analyzing the intent behind the production of the narratives of Tokugawa legal cosmology, this dissertation makes the case against totalizing generalities about the relationship between Tokugawa religion and Tokugawa law in general or during any particular period. The story of Tokugawa legal cosmology is a story not simply of a singular “Buddhism” in conflict with a singular “Confucianism” but of a myriad of particular Buddhisms and Confucianisms deployed in the service of legal racionation against themselves and one another at particular times and over the course of time. Focusing on periods of crisis, this work considers the articulation of Tokugawa law at times when social and political conditions demanded new responses from both government and law. Looking closely at laws issued in these historical contexts, instead of finding common themes we find tactical reimaginations by interested actors, and instead of shared cultural understandings we find idiosyncratic interpretations that reflect multiple, open conversations occurring simultaneously. These narratives offer a new viewpoint from which to understand social dissensus, and particularly the types of arguments that shaped Tokugawa law. The competition among legal cosmologies found across the Tokugawa period calls into question the totalizing characterizations of Tokugawa law that remain common in legal scholarship and are still commonly used to explain the impact of Tokugawa law on Japanese religion. The constant conflict between various legal cosmologies belies the idea that Tokugawa law was static across the period, or that Confucianism held a preponderant intellectual influence over Tokugawa jurisprudence. At the same time, the ebb and flow of different strands of cosmological speculation calls into question any alternative teleological narrative for Tokugawa law.