Explaining Plague in Early Modern Europe: The Role of Contagion in the Theories of Girolamo Fracastoro and Thomas Willis.

ABSTRACT

From the famous pandemic known as the Black Death, to the successive outbreaks of plague that continued to decimate the continent for the next three hundred years, the threat of plague was an almost constant presence in the lives of medieval and early modern Europeans. Thus, it is not surprising that various interpretations regarding plague causality arose during this period and were documented in medieval and early modern texts. Given that observation seemed to confirm person-to-person and object-to-person transmission of plague, it is also not surprising that theories of contagion can be found among these explanations. What may be less apparent, however, is that these theories of contagion did not necessarily occur in opposition to, but rather coexisted with, alternative explanations of plague causation, such as divine intervention or, perhaps more importantly, miasma, in which the air itself was thought to be the source of disease. Attempts by some historians to distinguish between the physicians, who supposedly denied contagion in favor of miasma, and the general public, who recognized the contagious nature of certain diseases, are at best oversimplifications, as there is clearly evidence for belief in contagion as a mechanism for plague transmission among both physicians and the general public during this period.

Historians of medicine have, however, tended to either dismiss early modern theories of contagion altogether, to assign too much importance to a perceived debate between contagionists and miasmatists, or to focus on those theories, such as “seeds of disease” or contagium animatum, that seem to bear some resemblance to modern germ theory. In this thesis, I take issue with these positions in two ways. First, I argue that transmission of plague by contagion was a well-established and important explanatory tool for early modern physicians seeking to make sense of plague outbreaks. Second, I argue that there were many different and competing theories of contagion during the early modern period. I suggest that part of the historiographic confusion on the issue of pre-modern notions of contagion stems from the very plethora of theories of contagion. Looking from the vantage point of the twentieth-century acceptance of one theory of contagion – germ theory – historians have failed to appreciate the variety of forms that contagion theory took in the past. To demonstrate these points, I first provide a survey of medieval and early modern explanations of plague, as well as an assessment of the relative importance of contagion among these explanations. I then focus intensively on the ideas of two early modern physicians, Girolamo Fracastoro (1478-1553) and Thomas Willis (1621-1675). In my discussion of these two, I point to some of the range and diversity of early modern theories of contagion.