The vagaries of medical explanations

Science prides itself on its scientific explanations. A good scientific explanation does not vary, but still accounts for what it purports to account for.[1]

The classic example of a good scientific explanation is that the tilt of the Earth’s axis accounts for the seasons due to the angle at which light arrives on the planet—straight on (at 90% to the surface of the planet) in summer vs. more angled in winter. With this Newtonian/mechanical explanation, humans no longer had to come up with deity stories, such as Demeter (goddess of spring) being sad and making the Earth cold when her daughter Persephone was kidnaped by Hades (god of the underworld). You can change these stories (explanations) however you like to suit the phenomenon. The axis-tilt explanation is universal (does not change for any solar system). Something else in favor of the axis-tilt explanation for the seasons is that it is a planetary explanation for a planetary phenomenon.

Medical explanations are quite different. Doctors mostly accept with reverence explanations at a lower or more fundamental (i.e., smaller, more biochemical, more molecular) level than the scale of the human body. In medicine there aren’t good mechanical explanations (like the axis-tilt example) for the diseases we treat (though heart valve issues come to mind). Our prime tool for finding a truth is the randomized controlled trial, which is theoretically true but in practise too expensive to get a study powered enough, statistically speaking, to say anything conclusive. The classic line at the end of most articles is “more studies are needed.” Furthermore, medical knowledge seems to bounce around over time (e.g., beta blockers are in this decade, out the next, and in the one after that).

In physics there are explanations like the axis-tilt example above because ridiculously simplified assumptions are made, but in biology one can’t do that. The biosphere (say 10−4 m for a small bacterium to 103 m for a giant mycelium) is right at the midpoint of the scales that physics spans (10−33 m for the Planck length to 1026 m for the size of the known universe). For the physicist, biology is too complex to simplify assumptions, and we “flounder on the shores of confounding variables” with our statistics.[2]

Here is a medical explanation that might fit the bill. A human body has three billion heartbeats (or a maximum of 120 years) and that’s it. Again, this is somewhat statistical and descriptive versus truly explanatory. 

Do any BCMJ readers have any good medical explanations to offer?
—Mark Elliott, MD, FRCPC


1.    Deutsch D. The beginning of infinity: Explanations that transform the world. Penguin Random House, 2011.

2.    Pearl J, Mackenzie D. The book of why: The new science of cause and effect. Basic Books, 2018.

Dr Elliott is a staff anesthesiologist at Providence Healthcare in Vancouver.

This blog post has been peer reviewed.

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