Demographic Crises
Learned Opinion and Measures
From the time it was obvious that this disease was something extraordinary—which is to say, almost from the first weeks—people naturally turned to the wise for advice and explanation. Or, as the wise are prone to do, the advice was offered unasked. One of the more noted of the opinions came from the faculty of the University of Paris, who were asked by the French king. Their response was that there had been a conjunction of planets in 1345 that caused a corruption of the air. This theory was in accord with ancient teaching, current thinking, and popular opinion that the quality of air itself caused sickness or health. A related opinion blamed the earthquakes that had struck the Near East over the previous few years, thereby releasing noxious fumes. Yet another related opinion blamed the exceptionally bad weather that had troubled the Mediterranean recently, for it was widely held that the tropical regions held deadly airs.
The wise were hard-pressed to understand why some people got the disease while others did not. Here they relied on the ancient theory of the four humors, four fundamental qualities of all living beings as well as the inanimate world. Since the evil air clearly came from areas of heat (tropical or underground), those with hot temperments were especially vulnerable while those who were cool were not.
It all sounds rather silly and it's easy to make fun of these ideas, but it's clear from reading passages that the learned of Europe were genuinely trying to think their way through the problem. The trouble was, the event was unprecedented (not really, but the 6th century plague was so long ago that no one knew of it). Nothing in their current state of knowledge gave them any clues. In fact, new diseases were all but unknown, so they didn't even have a way to go about thinking about something new.