The Fixation of Belief in Medicine
The role of reason versus evidence
Why do we believe what we believe in medicine? How does a new idea become accepted as “true”?
Charles Sanders Peirce (1839-1914) was a brilliant American philosopher from a prominent New England family who never achieved mainstream respectability among the academics of his day, but is now regarded as one of the greatest minds of the past two centuries. One of his most well-known works is his essay "The Fixation of Belief" published in 1877. I have posted an edited version of his essay; it is well worth reading in its entirety.
In the first part, he talks about how people come to believe what they do through a process of moving from doubt (a state of irritation and uncertainty) to belief (a state of repose and certainty). Beliefs are marked by the fact that people will act because of them. The second part of the essay is focused around his claim that there are four methods of moving from doubt to belief, that is, four methods for the fixation of belief:
1. the method of tenacity
2. the method of authority
3. the method of reason
4. the method of science
The method of tenacity is simply that one chooses to believe something, and clings to it regardless of the facts. The second method appeals to authority, as Peirce says the most common and most stable method, employed by governments and religions from time immemorial. The third method, an appeal to reason, is of a somewhat more recent origin, its modern incarnation starting back sometime in the middle ages, and still very much in fashion with the educated crowd, as we shall see. The fourth method is that of science, or the application of logic to evidence found in the real world, an empirical approach. Peirce views this as a progression from more primitive to more advanced methods, but also acknowledges the unique strengths of each.
Examples of the first two methods are rampant in everyday life. Although tenacity and appeal to authority are far from dead methods in medicine as well, I wish here to focus on the third and fourth methods: reason and science.
To be clear, Peirce is not suggesting that reason is somehow an unworthy method. Obviously it plays an invaluable role on its own in many situations, and indeed in science itself. He is instead referring to a method where a thought passes from doubt to belief because it is pleasing to the reason, without corroborating evidence from outside the mind of the reasoner. He cites metaphysics as a field where this method is rampant, but I argue that we can find many examples in medicine, and that in fact this is the preferred method when empirical evidence is considered lacking.
In times gone by, relying upon empirical evidence for a medical practice, say bloodletting, was impractical because there was no evidence. In fact there was almost no medical science to begin with. Physicians were trained to think in terms of the bodily humors: blood, yellow bile, black bile, and phlegm. Imbalances of these led to disease. If blood levels were high, then bloodletting would, logically, reduce it, ergo bloodletting was believed to work. The fact that it had never been actually demonstrated to work didn't seem to enter much into the conversation. Here was a belief founded on authority, that of Galen and other ancient sources, and a mere practitioner would not think to seriously doubt it. Still a few such things have been "grandfathered" into the knowledge base of the average physician, and are not given a second thought.
This state of affairs changed over the nineteenth century with the rise of the scientific method, and by the late twentieth century, robust methods for testing ideas in medicine had evolved.
Great respect accrued to those who could explain how the body works, and in particular how diseases arose.
The major source of funding for medical research in the US, the National Institutes of Health, became dominated by scientists, some medical doctors but many not, whose focus was on working out just how diseases arise preferably in as much detail about their mechanisms as possible. This was underpinned by a belief that in order to effectively treat a disease, it is useful to know these mechanisms. This is of course often true.
But this is not the only, or in fact not even the most common, way in which effective treatments are discovered. Many interventions have been found to work through empirical means, while the underlying mechanism remain completely obscure. Perhaps the greatest example in history is the invention and adoption of vaccination, starting possibly in China around the eleventh century and coming into wider use in the West by the end of the eighteenth century thanks to the efforts of Edward Jenner and others. Understanding of the immune system, in fact awareness of its very existence, did not arrive until much later.
But this belief about the usefulness of knowing the disease process in detail morphed at some point into the idea that such understanding is necessary before a new treatment can be accepted as valid practice by respectable people. This thinking extends beyond treatments to include other dimensions of medical knowledge, such as whether to credit a new observation about the relationship of certain symptoms and signs to others is to be taken seriously, or the connection between, say, certain infective agents and chronic symptoms (e.g. "chronic" Lyme disease).
This is why so often when a new suggestion for a medical treatment is proposed, or a new connection between some exposure and a disease, it is immediately met with the demand to know the mechanism. By mechanism is meant the cellular and molecular factors and interactions underlying its effects. This is unless this demand can be countered by abundant empirical evidence of the highest quality so that the fourth method, science, can be called on for support.
But this kind of scientific empirical evidence is often lacking; there are so many diseases, and clinical trials are so expensive and restricted by governmental rules and privacy concerns and a score of other factors, that falling back on method three is quite common indeed. If we know the mechanism, then we can say that the claim is "pleasing to reason" so we might credit it as true.
Because of this tendency, there are many objectively observed phenomena in medicine that have not been incorporated into mainstream medical thinking because their mechanism is unknown.
The underlying mechanism for many (most?) treatments and some diseases are not understood or poorly so. But present physicians with a truly new idea, and they will cry for the mechanism, unless or until you can hit them over the head with the empirical evidence.
It would behoove us to separate phenomena from explanations for phenomena. Phenomena can exist even though they "don't make sense". If they have been definitively established as being true, reproducible phenomena, then it is our beliefs that need to be revised, not reality.
One of the best examples I know is that of fecal transplant for the treatment of life-threatening C. difficile colitis. This is a very serious disease where the colon is markedly inflamed, and can lead to sepsis and death. The cause is a disruption of the normal ecology of the bacteria in the gut, usually brought on by aggressive antibiotic treatment for some other condition. It can be resistant to treatment and can recur. Over a hundred years ago, veterinarians discovered they could cure the condition by transferring feces from a healthy animal into the colon of the diseased animal. But this method was not tried in a human until 1958, and even then was ignored by essentially all medical researchers until the late 1990s, and not adopted by mainstream practitioners until around 2010. (Even now it is not the first line method.) Once it was tried, patients at death's door in the ICU walked out of the hospital a few days later. It's efficacy was stunning. Why wasn’t it used much earlier? How many patients died (or had a total removal of their colons) over those many years?
In part fecal transfer was not adopted because it didn’t make sense to doctors; the vital role of the gut microbiome was not understood until the 1990s and took another 15 years or so to percolate into the consciousness of everyday medical practitioners. Once the role of the microbiome was understood, then it made sense that fecal transplant could work, so then it was pursued. The mere fact that it actually had for a very long time been seen to work (in animals) was not enough.
Another example is the use of oral vancomycin for the treatment of primary sclerosing cholangitis (PSC). There is no known effective treatment for PSC endorsed by mainstream medicine, but vancomycin has been demonstrated in hundreds of patients to significantly improve the colitis and liver function markers in a reproducible fashion. When the drug is stopped, the symptoms and signs recur. It is not a cure, and not all patients respond, but in those that do it evidently affects the microbiome is some favorable way to stave off the worst effects of the disease. Only a tiny fraction of PSC patients receive this drug at present, and it is often denied by insurance coverage. The professional medical societies for liver and colon diseases do not acknowledge its benefits. I have personally been involved in trying to get a clinical trial off the ground, but because there is no money to be made (vancomycin is a generic drug), and because other researchers are already committed to competing efforts (largely drug trials for pharmaceutical companies), we have so far been unsuccessful in launching a trial.
Here is an example of a reproducible phenomenon, but the mechanism is not known in any detail, so it is not possible to tell the professional opinion makers why using oral vancomycin should be "pleasing to their reason". Enough empirical scientific evidence has not yet accumulated to convince them otherwise.
Meanwhile, the phenomenon of its benefit carries on, as reality tends to do, and untreated patients suffer and die in the meantime.