I've finished Steven Johnson's The Ghost Map. This post as well as this, this, and this one constitute my thoughts about it. While the putative subject of this excellent book is the London cholera epidemic of 1854, it is actually about something far less specialized and more far reaching - changing minds. Johnson tells us of the slow but seismic shift from the theory that diseases were caused by foul air to germ theory in general and, in the case of cholera, the notion that those germs infected our drinking water via its contamination by waste water.
The narrative relates this in a series of stages that move from - the original miasma theory, the counter-theory of waterborne infection, the logic or wisdom that supported the miasma theory, what made it compelling and why people held onto it for so long. Then, rather than any sort of eureka moment of discovery - such a popular way of characterizing scientific discovery - the eventual change, due to the dogged persistence of one man, Dr. John Snow, and his eventual winning over Henry Whitehead, the clergyman of the neighborhood most impacted by the outbreak.
The press and Board of Health were staunch defenders of the miasma theory but Johnson observes:
So often what is lacking in many of these explanations and prescriptions is some measure of humility, some sense that the theory being put forward is still unproven. It's not just that the authorities of the day were wrong about miasma; it's the tenacious, unquestioning way they went about being wrong. An investigator looking for holes in the theory could find them everywhere, even in the writings of the miasmatists themselves. The canary in the miasma coal mine should have been the sewer-hunters, who spent their waking hours exposed to the most noxious - sometimes even explosive - air imaginable. And yet, bizarrely, the canary seemed to be doing just fine...
As Snow observed many times in his writings during the period, there were countless cases of groups sharing the exact same living environment, breathing the exact same air, who seemed to have entirely opposing responses to the allegedly poisonous vapors. If the miasma was truly killing off Londoners, it seemed to choose its victims in an entirely arbitrary fashion...
Miasma had the support of the Chairman of the Board of health, Florence Nightingale - the nursing revolutionary, Charles Dickens, Engels - leading maverick minds of the day. It was an entrenched understanding that the noxious fumes produced when organic matter decomposed cause disease:
those telltale molecules - hydrogen sulfide, cadavrine - were clues pointing to a threat...methane and putrescine and cadavrine were the smoke. Microbes are the fire...John's Snows tireless interviews of residents lead a list of the address of each cholera victim and where they got their drinking water. He illustrated the connection by creating a map which won over Whitehead. Whitehead's insider-status and knowledge of the neighborhood residents lead to the discovery of the index case - the original case to which the infection can be traced. These two contributions together helped tip the balance and also pioneered our modern approach to epidemiology. But it took years longer for the general public to be swayed and John Snow died with little recognition for his work and without seeing that shift happen.
The committee begins with the assertion that cholera is transmitted via the atmosphere. When it discovers evidence that contradicts this initial assertion - a clear case that cholera has been transmitted by water - the counter-evidence is invoked as further proof of the original assertion: atmosphere must be so poisoned that it has infected the water as well. Psychologists call this type of faulty reasoning "confirmation bias":the tendency to force new information to fit one's preconceptions about the world.
Johnson concludes the book by connecting this slow but important change in thinking to his favorite subject - the nature of cities and other networks. I think the value of this book in in this story of how a network of minds possessing an idea creates a different force than the possession of that idea by any one individual. Consequently, the force needed to change it is different too. It is tempting to ridicule those who held on to the false miasma based theory of infection given our knowledge today. Even the eventual discovery of the cholera bacteria could not convince Edwin Chadwick, one of the leading Victorian physicians. However, no age is free from popular ideas supported only with arrogance, circular reasoning, and cemented in place by confirmation bias.
I'll connect this story to two of my own favorite concepts: 1- the idea that what you see is not necessarily what you get - it is more true to say that "seeing is believing." Our sense of sight is thought of as a great window on objective truth but in actuality, perception is strongly guided by our knowledge so it is not surprising to me how difficult it is to see a "new truth," if the old one not only guides our thinking but how we take in information with our senses as well. I post in depth on that notion here. Favorite idea #2 - It is the function of what Atul Gawande terms positive deviants (people who are in some way different from the norm in a useful way) to see through the miasma of faulty reasoning and to persist in telling us how we may look at old things anew and see clearly, see my post on Gawande's book and that notion here. In other words, the world does not benefit from everyone being alike. Many people are most comfortable when they are in the company of like minds and like beliefs, but eternally doing nothing but confirming what we already know makes us less able to see challenging truths, even when they are true, and less able to change. It is a sure recipe for halting our individual or societal progress - that is why Johnson's book is valuable. It is not a book about cholera, it is a book about ideas - hanging on to them, changing them, and letting them go when they are found to longer be useful or true. It is a human tendency to think in shortcuts and rest comfortably on common wisdom. Sometimes a deviant thinker has to jolt us out of our stasis into a new awareness. Dr. John Snow's ability to see a new pattern in the face of ridicule has since saved millions of lives. Positive deviants may be our world's most useful assets.