The search for the cause of yellow fever reveals a lot about the early American republic.
In August 1793, pestilence struck Philadelphia, the political capital of the nascent United States and its center of economic, cultural, and scientific activity. Those stricken exhibited high fever, chills, and delirium; in the worst cases, their skin turned yellow, and they emitted the infamous “black vomit,” a foul mixture made of partially digested blood that had hemorrhaged from the organs. Doctors who attended the sick identified the disease as yellow fever, a wasting illness that usually prevailed in tropical environments and struck down as many as half of those afflicted. By November, when the fever finally relented, more than four thousand people had died. Those who survived hoped that it would never return.
With the future of the republic hanging in the balance, thinkers hoping to prevent the disease posed a deceptively simple question: What caused yellow fever?
To the consternation of Americans, yellow fever reappeared annually from 1793-1805. The disease killed thousands in Philadelphia and New York, and hundreds more in Boston, Baltimore, Charleston, and New Orleans. Yellow fever was the most pressing natural problem of the era. Besides the deaths, the fever incited frantic mass evacuations. It halted trade in the nation’s busiest commercial centers for months at a time and led to burdensome quarantines and expensive sanitary reform measures. To many, yellow fever also seemed to erode public virtue, the cornerstone of a healthy republic, as fearful citizens turned against each other. For many others, the fever constituted a direct challenge to American exceptionalism, the pervasive belief that Americans were God’s people and were destined to escape the cycles of history that doomed past peoples.
With the future of the republic hanging in the balance, thinkers hoping to prevent the disease posed a deceptively simple question: What caused yellow fever? Understanding the cause of the disease would offer clues about how to prevent it. Almost a century before Walter Reed identified the mosquito vector (the Aedes aegypti mosquito) responsible for spreading yellow fever, opinions about the cause of yellow fever congealed around the two dominant models for understanding disease. One group, the “localists,” believed that yellow fever arose from clouds of noxious matter called miasmas, which were generated from within cities. As proof they argued that yellow fever occurred only within the boundaries of cities, never beyond. The other group, the “contagionists,” claimed that yellow fever was caused by portable particles of contagious matter, which were imported from abroad. They showed that outbreaks of the disease occurred only after the arrival of infected vessels. In short time, the dispute devolved into a bitter controversy that divided thinkers.
Far from splitting along political lines, investigators actually shared more similarities than differences. They were almost all devoutly religious and well-educated and they cast themselves as gentlemen and natural philosophers. Most, though not all, were trained doctors though as lexicographer, Noah Webster wrote, “I . . . consider the question as resting principally on fact, and not on medical skill; therefore proper to be investigated and discussed by any man who has leisure and means, as well as by physicians.” Indeed, most early republicans embraced the ideal of open and egalitarian public discourse, and so viewed claims to authority with suspicion. Truth claims rested not on the authority of the claimant, but upon the approval of the public.
Truth claims rested not on the authority of the claimant, but upon the approval of the public.
Only upon closer examination of the investigators do their deeper philosophical differences come into view. Localists embraced the essential precepts of the latest scientific methodologies—knowledge of nature was to be attained inductively, through the slow accumulation of empirical facts and data. As pious Protestants, they also believed the natural, its laws and its wonder, revealed the will and design of God. Localists believed that God had endowed human beings with an innate rational capacity known as common sense, a faculty with a two-fold nature: it was at once the perceiving organ of the mind itself, and it was the obvious, common-sense truths it detected in the world. Common sense became in the hands of localists a malleable tool that allowed them to grasp the underlying logic of the world, to unravel its mysteries, and to find truth; it was a concept devised to free inquirers from crushing skepticism and validate self-evident knowledge.
Contagionists were no less pious or scientific, and perhaps no less philosophical than the localists, but they refused to let the same considerations enter into their inquiries. Taught through apprenticeships, in hospitals and with hands-on experience, they tended toward materialism, evidenced by a predilection for surgery (a mere technical skill, according to university-trained physicians, and one they looked on condescendingly) and experimental chemistry. They consistently criticized the localists for their speculations and flights of fancy, and they adhered more strictly to the facts of yellow fever. Contagionists even sometimes admitted that local environmental conditions might activate particles of yellow fever into epidemic proportions. They focused principally on tracing and intercepting the pathways of the contagious particles, which they thought were ultimately responsible for yellow fever. For them, no arguments, no rationales, no elaborate justifications negated the convincing and well-founded fact that infected vessels arrived before every outbreak, and that the first victims came from those pestilential vehicles or nearby.
Despite their convincing and well-founded arguments, the contagionists ultimately failed to hold public opinion, and the localist perspective prevailed in the yellow fever debate. One factor behind their victory was purely practical. Contagionists did not publish as voraciously as localists, nor did they occupy university positions from which to perpetuate their ideas to scores of young students. More importantly, localist explanations better appealed to common sense, they more plausibly depicted yellow fever as an entity that conformed to the apparent design of the world, one that could be understood with common faculties of the mind. They persuaded audiences that locally generated diseases occurred in cycles that appeared throughout history; they rationalized the chemical construction of the matter that brought on yellow fever, and explained its emergence from normal chemical reactions; and, finally, they used evidence of design and scripture to explain why it would exist in God’s world, and how people could stop it. In a religious and enlightened society, where a learned public followed the debate with great interest and anxiety, the plausibility of localism outweighed the facts of contagionism.
The controversy produced one of the most innovative and expansive outpourings of scientific thought in American history. As scientific controversies often do, the yellow fever questions forced investigators to question assumptions, and to articulate points of view that normally remain unspoken. The yellow fever controversy thus opens an excellent and important window onto the life of the mind in the early United States, a time when intellectuals were busy crafting the institutions and ideas that they hoped would set the country on the path to prosperity. Though the disease eventually left the American port cities, it left permanent rifts in the young nation’s medical and scientific institutions, and the legacy of the vituperative conflict it generated helped to convince Americans that unanimity of sentiment and opinion were impossible to achieve. People would be divided, despite the best of intentions, a lesson which would make the search for the cause of yellow fever one of the formative episodes of early American history.