When defending the causal efficacy of a scientific theory, such as germ theory, it is critically important to ensure that the story telling embeds both the casual arguments and mutually exclusive evidence that proves one explanation is correct and the other is false. Telling compelling stories is nice, but defense requires logical rigor, not just emotions. The SUCCES acronym (Simple, Unexpected, Concrete, Credible, Emotional, Stories) created by the Heath brothers in their book Made To Stick is not enough for defending science. We need storytelling that communicates the logical exclusivity between the central dogma and the important competing theories that are rejected by that rhetorical structure.
Recently a post claiming that germ theory is false appeared in my Facebook feed. The author claimed that disease is not contagious. I don’t know what claim for the origin of disease was behind the claim, but I am not going to get on their e-mail list to find out. It is probably something along the lines of systemic vulnerability which makes the presence of germs a symptom, a merely correlated factor, not the cause of the disease.
The author was promoting a “secret protocol” that would cure any disease. He can be confident that some portion of the people who enact his protocol will get better and gratefully attest to the miracle cure that he provided. Those that don’t get better will mostly move on with their lives without a second thought for the failure of his protocol. And those few who don’t get better and decide to call him out will be dismissed as having failed to do it properly. That will happen no matter what ultimately caused the disease, so he and the other quacks have a reliable business model.
After seeing the post I asked, “Would the defenders of germ theory please articulate the causal argument, explain how the experimental data would look in the case of support for AND against the germ theory explanation, and then point out the experiments that provide causal proof? This would be really helpful to those of us that believe in germ theory but do not have the chops to fully defend it.”
My helpful friend Greg immediately found a couple of videos about germ theory to answer my call:
“It's not hard to find sources. it took me all of sixty seconds to find these.
https://www.youtube.com/watch?v=N9LC-3ZKiok
https://www.pbs.org/video/how-we-discovered-germs-ots3wv/
The problem is that these videos are nice story telling ABOUT the parade of scientists who developed germ theory but they fail to satisfy my request. They are nice historical reviews but they do not articulate the causal argument and neglect to convey how the relevant experiments isolated causal factors in a manner that enables the result to provide mutually exclusive evidence for one explanation over another.
Here’s a NatGeo video that explains one of Pasteur’s demonstrations of vaccination on sheep, it is closer to what I was requesting:
https://www.youtube.com/watch?v=1lLNZQVPpQA
It does not explain what the competing hypothesis was, so as good as it is, it still does not quite meet my criteria.
One version of what I want is embedded in Steven Johnson’s great book The Ghost Map. He tells the story of the cholera epidemic that hit London in 1854 by focusing on both Doctor John Snow (as the TED-Ed video does) but also his antagonist-collaborator the Reverend Henry Whitehead who wanted to prove him wrong about the possibility of a particle in the water. Whitehead was instrumental in gathering good data because it was his parish in which the outbreak of cholera happened. He was a trusted figure in the community so he was able to thoroughly document the deaths and contribute substantially to the observational and logical corpus that enabled them to work out what was really going on.
The key to the causal argument is pitting the expected data pattern from Whitehead’s miasma theory against Snow’s proto-germ theory (germ theory as we know it today wasn’t fully developed until decades later by Pasteur, Lister, Koch, etc.) For instance, the prevailing winds through that area of London would have carried the “miasma” in a particular direction from the source, a water well, perpendicular to a Regent’s Road that had very few intersections. This particular feature cut the neighborhood of the well pump off from other neighborhoods. This means that if miasma were the true cause of the disease the wind would have carried the disease over the road and into the cut-off neighborhoods. That was not the case.
Snow’s theory was that a particle in the water was the cause of the outbreak. After the data was collected and mapped the pattern showed that households that had to take fewer steps to get to the Broadstreet water pump tended to have more deaths than those that had to take more. The pattern was strongly correlated with the steps but not the wind.
But the anomalies in the data were important, too. The nearby brewery had almost no cholera deaths because despite using the same water, the brewery employees drank beer, not straight water. The brewing process must have been eliminating the cholera.
Another anomaly was a woman in an outlying area who died of the cholera. Upon investigation it turns out that she used to live near the Broadstreet well and had her children bring her that particular well water, which ended up killing her and many of her children, too. There were even more anomalies that consistently reinforced the idea that the cause had to be in the water, not the air.
Finally, Snow and Whitehead were able to find patient zero of that neighborhood outbreak was an infant whose mother dumped the soiled diapers into a basement cesspool, a common practice of the time. That particular cesspool was less than 3 feet from the Broadstreet well and had a leaky wall that introduced its foul contents into the well. Uncovering this specific information required two excavations because the first was done under the direction of miasmists who were not thorough enough. The second excavation was undertaken with the particle theory in mind so the excavation was done in a manner that could reveal relevant facts. Ultimately, the Broadstreet well was the source of death for the whole neighborhood, including a variety of outliers.
The point is that compelling story telling is only part of the challenge that I posed. The critically important part is conveying how the evidence supports a mutually exclusive logical interpretation in support of one theory against the competing theory. I agree that the burden of proof is on those who make claims against germ theory, but we need to be proactive about making precise arguments in the context of compelling stories. Sloppy arguments embedded in compelling stories might be fun, but they are not doing the work that needs to be done.
To restate my request to defenders of germ theory: tell (and share access to) compelling stories that embed the logic of mutually exclusive hypotheses about the causes of disease. A thorough defense should be able to explain what pattern of data the opposition needs to present in order to both undermine germ theory and support their own. If they come up with that pattern, defenders need to admit that a challenge is in play and figure out how each theory can be further tested to settle the challenge.
It has also turned out in prior scientific controversies that mutual exclusivity itself proves to be the error. When physicists concocted the double slit experiment to settle the debate about whether light is a particle or a wave both sides legitimately claimed the results supported their hypothesis. Eventually, every legitimate physicist had to admit that both sides were right and light can have both sets of properties.
Maybe germs are only part of the causal story. If the critics have some legitimate data that calls germ theory into question, we should be grateful. If they are making specious arguments then that should be demonstrable with data we already have. We need some storytellers who can be true to the logic of the experiments that can settle causal questions with mutually exclusive interpretations of good data.
I get that we should not address every crank who objects. Don’t feed the trolls, right? However, we also should be careful not to dismiss them entirely because if they build up sufficient political power they can simply deny the relevance of expertise, as the current federal administration here in the USA is doing. There is a political dimension to defending science that we ignore at our peril. We need skillful story tellers who can embed the logic of scientific argument in their stories, not just focus on a parade of interesting people.
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