Eighteenth-and early nineteenth-century ideas about the occurrence and spread of epidemic disease were complex and contested. Although many thought that diseases such as plague, typhus, and cholera were contagious and were communicated from person to person or via the medium of goods, others believed that they were the product of atmospheric change. Moreover, as historians have emphasized, the early nineteenth century saw a move from a multifactoral, climatic etiology toward one that prioritized specific local corruption of the atmosphere caused by putrefying animal and vegetable matter. In this paper, I extend this analysis by linking to recent literature on dirt and disgust and exploring the importance of theologies. I examine the work of two key figures in the history of British epidemiology, Charles Maclean and Thomas Southwood Smith, and demonstrate how the latter’s increasing emphasis upon the causal agency of filth was structured by his Unitarian faith and his belief in a universally benevolent God.