"The philosopher K Codell Carter's authoritative study of the transition from an assumption that diseases have multiple causes to the modern belief in universal, necessary causes is such a book. For decades, historians have fruitfully explored the social history of modern medicine to the neglect of its intellectual history. Carter's careful dissection of the changing concepts that led to the germ theory of infectious diseases provides a sturdy base on which historians may rectify this imbalance and investigate previously unasked questions about the history of medicine in the last hundred years." (Medical History).