Medicine is not only a cultural system of its own. It also performs specific roles in the broader culture of society at large. This article examines the role of medical arguments in the critique of "enthusiasm" on the eve of the Enlightenment. The enthusiasts, who claimed to prophesy and to have direct divine inspiration, were increasingly seen in the seventeenth century as melancholics. With the decline of humoral medicine, however, the account of melancholic disturbances--including enthusiasm--that was offered tended to be chemical, mechanistic, and clearly corpuscular. Protestant ministers, in adopting such an account of enthusiasm, also adopted a strict distinction between the realm of the mind (to which true prophecy belonged) and that of the body (in which they located the phenomena of enthusiasm). Such a distinction served in turn to demarcate more specifically the limits between the clerical and medical professions. Yet in relegating the treatment of enthusiasts to the physicians, rather than seeing the enthusiasts as heretics, the ministers stood in danger of relying too much on a secular profession and secular arguments, thus paving the way to a more general secularization of the ideological basis of the social order.