Book Summary: The Laws of Medicine by Siddhartha Mukherjee

“The discipline of medicine concerns the manipulation of knowledge under uncertainty.”

Doctor Siddhartha Mukherjee, oncologist and best selling author, opens ‘The Laws of Medicine’ with an anecdote from his training years. He sets up the course for the book in a description of his time spent with a surgeon whose intuition and knowledge were so great that he allowed interns to complete procedures while he observed, knowing that he could predict, intervene and fix any slip ups that occurred. The medical ‘intuition’, and it’s role in navigating the unpredictable nature medical practice is a focal point of the book.

“It’s easy to make perfect decisions with perfect information. Medicine asks you to make perfect decisions with imperfect information.”

In the three laws of medicine which he has accumulated from his clinical experience, Mukherjee addresses the glaring probabilistic, almost ‘lawless’, nature of Medicine and how physicians can navigate “the reconciliation between knowledge (certain, fixed, perfect, concrete) and clinical wisdom (uncertain, fluid, imperfect, abstract).”

Law One: A strong intuition is much more powerful than a weak test

“It is here that an insight enters our discussion—and it might sound peculiar at first: a test can only be interpreted sanely in the context of prior probabilities.”

When conducting a clinical test, there is always a margin for error. This error can vary per test, per patient ect, however Mukherjee points out the fallacy of relying entirely on tests and not enough on professional insight. In an anecdote concerning an AIDs patient who’s case was hard to crack Mukerjee points out the doctors role as data collectors. By collecting enough data from examinations, they can stack up probabilities for whether the patient has diseases x or y, and then conduct tests to confirm or strike their hypothesis. If conducting tests without professional insight, interpreting them can become relatively more speculative hence more likely to be a false positive or false negative, than if the test had been ordered with knowledge of the patient’s context- he also backs this up with explanations of Bayesian analysis:

“Pure statistical reasoning cannot tell you the answer to the question—but common sense does. The fact that the coin has landed “heads” twelve times tells you more about its future chances of landing “heads” than any abstract formula. If you fail to use prior information, you will inevitably make foolish judgments about the future. This is the way we intuit the world, Bayes argued. There is no absolute knowledge; there is only conditional knowledge. History repeats itself—and so do statistical patterns. The past is the best guide to the future.”

Law Two: “Normals” teach us rules; “outliers” teach us laws.

Next he reflects on the importance of outliers. Using Kepler’s discovery of ellipitical orbits, which was precipitated due to his fixation on understanding outliers to the traditional Copernican theory, Mukherjee draws parallels to the importance of cases which buck the trend when it comes to medical advancements. From Cancer drugs to understanding Autism ( to establish the cause and effect relationship between ‘refrigerator mothers’ and their emotionally distant offspring), he notes the importance of scientific pursue these outliers to form ‘laws’ rather than outcomes which confirm hypotheses.

“Think about the vast range of medicines and surgical procedures not as therapeutic interventions but as investigational probes.”

Law Three: For every perfect experiment, there is a perfect human bias.

Finally Mukherjee pauses to reflect on bias in Medicine. Bias is inherent to all sciences as extracting wisdom involves ‘human perception, arbitration and interpretation’ . In medical science the clouding of bias is particularly acute due to hope – ‘the tender centre’ of medicine which wants treatment to save or improve human lives- and illusion. To illustrate this he refers to the surge in Radical Mastectomies that occurred in the early 20th century, despite mounting evidence that the success of the intervention didn’t justify its widespread use. Mukherjee also reflects on the veneration of randomized controlled trials and the limits to their scope. He notes the very effect of running a trial changes the nature of the subject, once again limiting the extent they can be generalized for patient populations.

Loaded with historical and philosophical anecdotes ‘The Laws of Medicine’ makes for an enjoyable read. I’ll leave you with my favorite quote ( judge me all you want 🙂 )

In Harry Potter, the philosophical treatise disguised as a children’s book, a teacher of wizardy asks Hermione Granger, the young witch-in-training, whether she wishes to learn the Magical Laws to pursue a career in magic. “No” says Granger. She wishes to learn the laws so she can do some good in the world. For Granger, the magical laws do not exist to perpetuate magic. The exist as tools to interpret the world.

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