The concept of ‘religion’ as modern, European-derived, and therefore problematic in premodern and Asian contexts is well established, but leaves us with a problem: if the church/state sacred/secular dynamic is a modern misconception even in England, as Fitzgerald argued, then how should we go about examining the central place of specific institutions, behaviour, and belief in the workings of medieval Japanese society that have formerly been classified or understood as ‘religious’? Abandoning ‘religion’ as a separate field of study from the ‘secular’ in Japanese history has the paradoxical effect of drawing attention to the pervasive centrality of activity, performance, mentality, and observance to every aspect of medieval life. Elements of practice, performance, and the sacred were essential, core, components of the functioning of public and private governance from the imperial system to local landholding. The great temple shrine complexes of the medieval period were centres of organisation, authority, and legitimacy, which are best understood not as ‘religious’ complexes which were also ‘economic’ and ‘political’ powers, but as institutions whose authority cannot be separated out into separate (modern) categories of ‘economic’, ‘judicial’, or ‘religious’ authority. Such distinctions cut across the deeply interconnected nature of law, landholding, family, lineage, place, and belief in the period, the networks and systems by which medieval life was ordered, but they also cut across the way that they were perceived by those living within them: the ways in which people thought, behaved, and interacted with each other. In order to understand the workings of what we think of as medieval Japanese society, we must understand these connected systems as composed of elements that might look ‘religious’ or ‘secular’ to modern eyes, but which were complementary, indivisible, even, in the period.