In eighteenth- and nineteenth-century Britain, a bacterial infection which we now know to be caused primarily by a streptococcus, was killing women in childbirth at an alarming rate. The disease, called puerperal, or childbed, fever, was being transmitted primarily from doctor to patient by a doctor’s unwashed hands and filthy, contaminated clothing and linens. Despite this evident and, in retrospect, obvious vector, the doctors of this period never discovered how to prevent their patients from dying a gruesome and painful death. Many physicians wrote extensive accounts of the illness but often ended their works in despair, unable to find the cause. Much of the historical literature blames this befuddlement on personality traits of the physicians, arguing that egos and professional hostilities prevented the kind of cooperation that could have led to progress. This study attempts to show that this failure was not a product of personalities but of the modern physicians’ assumptions and logic. The assumptions were the stillpowerful, but often unnoticed, dictates about the human body handed down from ancient Greek medicine. The logical errors were a product of pre-scientific notions of definition, explanation, and evidence. The author argues that it was not a lack of data that thwarted the physicians, but a series of these intellectual roadblocks that prevented them from understanding and extended the terror of puerperal fever for another two centuries.