The idea of embracing uncertainty is a popular one in the physical therapy community and for good reason — the clinical environment is complex and our patients even more so. This complexity makes it difficult to determine what might be contributing to someone’s pain or what treatments actually produce meaningful effects — pulling any sort of signal from the noise is quite hard. This awareness of uncertainty in our clinical practice can help improve our judgement and maybe even reduce mistakes in our reasoning (such as hasty generalizations). But as they say, the difference between medicine and poison is the dose.
The problem with uncertainty is when we believe that since there is so much chaos and unpredictability in what we do, we believe everything to be equally uncertain and that assuming a position resembling any bit of certainty must be false. This appeal to uncertainty is essentially the inverse of a false dilemma where a dichotomous, black or white perspective is replaced with an indecipherable mess of gray, hence the title of this informal fallacy — “The Fallacy of Gray.” The issue with this type of reasoning is that the fallacy of gray places all premises on equal footing in that there is equal uncertainty in their validity, which is far from reality. It would be foolish to place the phlogiston theory of combustion in equal scientific standing to the oxygen theory of combustion solely due to the inherent uncertainty and complexity of the universe.
People often default to the fallacy of gray not as a way of reasonably appealing to the complexity of clinical care, but instead to undermine or reject evidence that goes against one’s beliefs. The fallacy of gray is often invoked in arguments involving alternative medicine, such as the debate that acupuncture works (in other words, demonstrates efficacy) or that acupuncture does not work. There is robust evidence that allows us to be as reasonably certain as possible that acupuncture has no meaningful specific effect and does not work across a litany of clinical conditions (1, 2, 3). An argument illustrating the fallacy of gray would vaguely appeal to the complexity of clinical care as reason to dismiss the results of well performed studies in order to suggest that the most reasonable position on acupuncture’s efficacy is actually somewhere in the middle — “We just can not be certain that acupuncture does not work and it would be foolish to adopt such a black or white stance.” This is then usually followed by a rationalization for the continued use of acupuncture on a “case by case basis” with poorly described expertise used to determine when acupuncture is truly worthwhile. What the fallacy of gray fails to do is provide specific and valid reasons as to why the premise that acupuncture does work should be placed in equal standing to the premise that acupuncture does not work, in the face of strong evidence suggesting that the positions are anything but equal in uncertainty.
While we should continue to embrace uncertainty, we should also be aware that along a grayscale there is an obvious distinction between a gray that is closer to black and a gray that is closer to white. It would be wrong to think that we are equally uncertain about all things in physical therapy practice. Just as there is a relativity of wrong, there is a relativity of uncertainty. We should strive to be both less wrong and less uncertain in our practice.