This thesis examines the appearance of humoral discourse in religious literature disseminated in England in the later medieval period. It employs focused case-studies drawn extensively from manuscripts and early printed sources to demonstrate the transmission of humoral theory in religious circles and how this changed over time, especially with the shift from Latin to the vernacular in the fourteenth and fifteenth centuries. By demonstrating the transmission of humoral ideas outside the medical sphere in England in this period, this provides evidence for a ‘medicalization’ of society at this time. However, this study also demonstrates that there was increasingly a ‘Christianization’ of medicine at the same time, evident in the appropriation of humoral discourse in religious literature including sermons, pastoral guides, Rules for religious, works of religious instruction, and devotional and mystical texts.