From Sin to Science: Astrological Explanations for the Black Death, 1347-1350

By Rebecca Johnson

Ex Post Facto: Journal of the History Students at San Francisco State University, Vol.18 (2009)

Introduction: By the time the first wave of the Black Death engulfed Western Europe, the validity of “natural” astrology was firmly accepted by literate elites. Associated with the revival of Aristotelian learning begun in the twelfth century, the concept that “superior” bodies such as stars and planets exercised at least a general influence on earthly events enjoyed a wide currency among clergy as well as laymen. A significant number of scholars doubted—whether based on the heretical implications of the idea, or their own empirical observations—that the stars actually determined the fate of individuals. But even they had to concede, on the evidence of the seasons and tides, that broader forces might emanate from the heavens. This naturalistic discourse of the stars ran parallel to (and often intersected with) the discourse of Christian apocalyptic, in which celestial bodies generally functioned as omens rather than causes. The rising prominence of both discourses during the fourteenth century ensured that the stars would play a central role in contemporary efforts to make sense of the plague’s devastation.


These efforts varied from deterministic analyses focused on the mechanical influences of the celestial spheres, to primarily apocalyptic readings that employed astrological illusions to buttress their authority. They also included accounts that, though mentioning astrology only incidentally, reveal how deeply embedded the idea that the planets were in some way responsible for events on earth had become in the plague discourse shared by the learned.

Although the degree of formal astrology employed in each varies, these accounts contrasted strikingly with contemporary arguments that the plague represented divine retribution for mankind’s sins. In this sense, they can be seen to represent the growth of a world-view that, if not quite “scientific” in the modern use of the word, was nonetheless increasingly deterministic and objective. This perspective was not necessarily irreconcilable with the idea of a vengeful God choosing to punish humanity for its trespasses at a particular moment in time. In the Aristotelian universe elaborated by scholastic thinkers, which received its definitive form in the Summa Theologica of Thomas Aquinas, God was characterized as the primum movens, or first cause, of all things. He might thus be understood as operating through proximate causes, using the planets as vehicles to communicate his wrath.

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