American Scientist has an erudite, detailed review of two recent books on John Snow, not the former secretary of the treasury but the doctor who solved the mystery of cholera in 19th-century London (spoiler: it was the water). Reviewer Christopher Hamlin likes the book okay but takes the authors to task for their “presentism”—roughly, for praising Snow in hindsight for being right while demonizing his contemporaries who advanced theories that happened to be wrong.
Hamlin says that the scientific community wasn’t ruled by folklore, superstition, and venality, as the books suggest, but rather that they had fairly reasonable, scientific paradigms that led them to disagree with Snow. For instance, other doctors criticized Snow’s theory because he simplistically assumed that the cause of cholera entered through the mouth because it caused problems in the gut. (Other theories at the time involved an inhaled pathogen.)
Seeing that modern medicine has shown that an STD cause body-wide immune deficiency, that listening to a song help fix a brain dysfunction, and that a bacteria entering through the mouth and can change the entire culture of a country, this particular paradigm of Victorian medicine doesn’t sound so backward.